USE Flag Index

---

Global USE Flags

Flag	Description
3dfx	Enable support for Voodoo chipsets, also called as 3DFX and TDFX
X	Add support for X11
Xaw3d	Add support for the 3d athena widget set
a52	Enable support for decoding ATSC A/52 streams used in DVD
aac	Enable support for MPEG-4 AAC Audio
aalib	Add support for media-libs/aalib (ASCII-Graphics Library)
accessibility	Add support for accessibility (eg 'at-spi' library)
acl	Add support for Access Control Lists
acpi	Add support for Advanced Configuration and Power Interface
adns	Add support for asynchronous DNS resolution
afs	Add OpenAFS support (distributed file system)
aim	Enable AIM IM protocol support
alsa	Add support for media-libs/alsa-lib (Advanced Linux Sound Architecture)
altivec	Add support for optimizations for G4 and G5/ppc970 processors
ao	Use libao audio output library for sound playback
apache2	Add Apache2 support
apm	Add APM (Advanced Power Management) support
aqua	Include support for the Mac OS X Aqua (Carbon/Cocoa) GUI
atm	Enable Asynchronous Transfer Mode protocol support
audiofile	Add support for libaudiofile where applicable
audit	Enable support for Linux audit subsystem using sys-process/audit
avahi	Add avahi/Zeroconf support
ayatana	Build in support for Ayatana notification using the libindicate or libappindicator plugin
bash-completion	Enable bash-completion support
bcmath	Add support for libbcmath
berkdb	Add support for sys-libs/db (Berkeley DB for MySQL)
bidi	Enable bidirectional language support
bindist	Flag to enable or disable options for prebuilt (GRP) packages (eg. due to licensing issues)
blas	Add support for the virtual/blas numerical library
bluetooth	Enable Bluetooth Support
bootstrap	!!internal use only!! DO NOT SET THIS FLAG YOURSELF!, used during original system bootstrapping [make stage2]
boundschecking	Add the bounds checking patch by Haj Ten Brugge, this will DISABLE the hardened PIE+SSP patches
branding	Enable Gentoo specific branding
bsf	Enable support for Apache Bean Scripting Framework (dev-java/bsf)
build	!!internal use only!! DO NOT SET THIS FLAG YOURSELF!, used for creating build images and the first half of bootstrapping [make stage1]
bzip2	Use the bzlib compression library
cairo	Enable support for the cairo graphics library
calendar	Add support for calendars (not using mcal!)
canna	Add support for the Canna kana to kanji conversion engine
caps	Use Linux capabilities library to control privilege
cdb	Add support for the CDB database engine from the author of qmail
cdda	Add Compact Disk Digital Audio (Standard Audio CD) support
cddb	Access cddb servers to retrieve and submit information about compact disks
cdinstall	Copy files from the CD rather than asking the user to copy them, mostly used with games
cdparanoia	Enable cdparanoia (audio CD ripper) support
cdr	Add support for CD writer hardware
cgi	Add CGI script support
cjk	Add support for Multi-byte character languages (Chinese, Japanese, Korean)
clamav	Add support for Clam AntiVirus software (usually with a plugin)
connman	Add support for net-misc/connman
coreaudio	Build the CoreAudio driver on Mac OS X systems
cracklib	Support for cracklib strong password checking
crypt	Add support for encryption -- using mcrypt or gpg where applicable
cscope	Enable cscope interface -- in vim for example
css	Enable reading of encrypted DVDs
ctype	Enable ctype functions
cups	Add support for CUPS (Common Unix Printing System)
curl	Add support for client-side URL transfer library
custom-cflags	Build with user-specified CFLAGS (unsupported)
cvs	Enable CVS (Concurrent Versions System) integration
cxx	Build support for C++ (bindings, extra libraries, code generation, ...)
dbi	Enable dev-db/libdbi (database-independent abstraction layer) support
dbm	Add support for generic DBM databases
dbus	Enable dbus support for anything that needs it (gpsd, gnomemeeting, etc)
debug	Enable extra debug codepaths, like asserts and extra output. If you want to get meaningful backtraces see https://wiki.gentoo.org/wiki/Project:Quality_Assurance/Backtraces
dedicated	Add support for dedicated game servers (some packages do not provide clients and servers at the same time)
dga	Add DGA (Direct Graphic Access) support for X
directfb	Add support for DirectFB layer (library for FB devices)
djvu	Support DjVu, a PDF-like document format esp. suited for scanned documents
doc	Add extra documentation (API, Javadoc, etc). It is recommended to enable per package instead of globally
dri	Enable direct rendering: used for accelerated 3D and some 2D, like DMA
dts	Enable DTS Coherent Acoustics decoder support
dv	Enable support for a codec used by many camcorders
dvb	Add support for DVB (Digital Video Broadcasting)
dvd	Add support for DVDs
dvdr	Add support for DVD writer hardware (e.g. in xcdroast)
eds	Enable support for Evolution-Data-Server (EDS)
emacs	Add support for GNU Emacs
emboss	Add support for the European Molecular Biology Open Software Suite
encode	Add support for encoding of audio or video files
enscript	Add enscript support to colourize code stored in the repository
evo	Add support for mail-client/evolution
examples	Install examples, usually source code
exif	Add support for reading EXIF headers from JPEG and TIFF images
expat	Enable the use of dev-libs/expat for XML parsing
fam	Enable FAM (File Alteration Monitor) support
fastcgi	Add support for the FastCGI interface
fbcon	Add framebuffer support for the console, via the kernel
ffmpeg	Enable ffmpeg/libav-based audio/video codec support
fftw	Use FFTW library for computing Fourier transforms
filecaps	Use Linux file capabilities to control privilege rather than set*id (this is orthogonal to USE=caps which uses capabilities at runtime e.g. libcap)
firebird	Add support for the Firebird relational database
flac	Add support for FLAC: Free Lossless Audio Codec
flatfile	Add dbm support for flat files
fltk	Add support for the Fast Light Toolkit gui interface
fontconfig	Support for configuring and customizing font access via media-libs/fontconfig
foomaticdb	Add support for the foomatic printing driver database
fortran	Add support for fortran
freetds	Add support for the TDS protocol to connect to MSSQL/Sybase databases
freewnn	Add support for FreeWnn kana to kanji conversion engine
ftp	Add FTP (File Transfer Protocol) support
gcj	Enable building with gcj (The GNU Compiler for the Javatm Programming Language)
gd	Add support for media-libs/gd (to generate graphics on the fly)
gdbm	Add support for sys-libs/gdbm (GNU database libraries)
geoip	Add geoip support for country and city lookup based on IPs
geolocation	Enable physical position determination
ggi	Add support for media-libs/libggi (non-X video api/drivers)
gif	Add GIF image support
gimp	Build a plugin for the GIMP
git	Enable git (version control system) support
glut	Build an OpenGL plugin using the GLUT library
gmp	Add support for dev-libs/gmp (GNU MP library)
gnome	Add GNOME support
gnome-keyring	Enable support for storing passwords via gnome-keyring
gnuplot	Enable support for gnuplot (data and function plotting)
gnutls	Add support for net-libs/gnutls (TLS 1.0 and SSL 3.0 support)
gphoto2	Add digital camera support
gpm	Add support for sys-libs/gpm (Console-based mouse driver)
gps	Add support for Global Positioning System
graphicsmagick	Build and link against GraphicsMagick instead of ImageMagick (might require USE=imagemagick if optional)
graphviz	Add support for the Graphviz library
gsl	Use the GNU scientific library for calculations
gsm	Add support for the gsm lossy speech compression codec
gstreamer	Add support for media-libs/gstreamer (Streaming media)
gtk	Add support for x11-libs/gtk+ (The GIMP Toolkit)
guile	Add support for the guile Scheme interpreter
gzip	Compress files with Lempel-Ziv coding (LZ77)
handbook	Enable handbooks generation for packages by KDE
hardened	Activate default security enhancements for toolchain (gcc, glibc, binutils)
hddtemp	Enable monitoring of hdd temperature (app-admin/hddtemp)
hdf5	Add support for the Hierarchical Data Format v5
hscolour	Include coloured haskell sources to generated documentation (dev-haskell/hscolour)
ibm	Add support for IBM ppc64 specific systems
iconv	Enable support for the iconv character set conversion library
icq	Enable ICQ IM protocol support
icu	Enable ICU (Internationalization Components for Unicode) support, using dev-libs/icu
idn	Enable support for Internationalized Domain Names
ieee1394	Enable FireWire/iLink IEEE1394 support (dv, camera, ...)
imagemagick	Enable optional support for the ImageMagick or GraphicsMagick image converter
imap	Add support for IMAP (Internet Mail Application Protocol)
imlib	Add support for imlib, an image loading and rendering library
infiniband	Enable Infiniband RDMA transport support
inifile	Add dbm support for .ini files
inotify	Enable inotify filesystem monitoring support
introspection	Add support for GObject based introspection
iodbc	Add support for iODBC library
ios	Enable support for Apple's iDevice with iOS operating system (iPad, iPhone, iPod, etc)
ipod	Enable support for iPod device access
ipv6	Add support for IP version 6
iwmmxt	Add support for optimizations for ARM iwMMXt instructions
jack	Add support for the JACK Audio Connection Kit
java	Add support for Java
javascript	Enable javascript support
jbig	Enable jbig-kit support for tiff, Hylafax, ImageMagick, etc
jingle	Enable voice calls for jabber
jit	Enable just-in-time compilation for improved performance. May prevent use of some PaX memory protection features in Gentoo Hardened.
joystick	Add support for joysticks in all packages
jpeg	Add JPEG image support
jpeg2k	Support for JPEG 2000, a wavelet-based image compression format
kde	Add support for KDE (K Desktop Environment)
kerberos	Add kerberos support
kontact	Enable support for the KDE personal information manager (kde-apps/kdepim*)
ladspa	Enable the ability to support ladspa plugins
lame	Prefer using LAME libraries for MP3 encoding support
lapack	Add support for the virtual/lapack numerical library
lash	Add LASH Audio Session Handler support
latex	Add support for LaTeX (typesetting package)
lcms	Add lcms support (color management engine)
ldap	Add LDAP support (Lightweight Directory Access Protocol)
libass	SRT/SSA/ASS (SubRip / SubStation Alpha) subtitle support
libav	Prefer libav over ffmpeg whenever both are supported
libcaca	Add support for colored ASCII-art graphics
libedit	Use the libedit library (replacement for readline)
libffi	Enable support for Foreign Function Interface library
libnotify	Enable desktop notification support
libressl	Use dev-libs/libressl as SSL provider (might need ssl USE flag), packages should not depend on this USE flag
libsamplerate	Build with support for converting sample rates using libsamplerate
libwww	Add libwww support (General purpose WEB API)
lirc	Add support for lirc (Linux's Infra-Red Remote Control)
livecd	!!internal use only!! DO NOT SET THIS FLAG YOURSELF!, used during livecd building
lm_sensors	Add linux lm_sensors (hardware sensors) support
lua	Enable Lua scripting support
lzma	Support for LZMA (de)compression algorithm
lzo	Enable support for lzo compression
m17n-lib	Enable m17n-lib support
mad	Add support for mad (high-quality mp3 decoder library and cli frontend)
maildir	Add support for maildir (~/.maildir) style mail spools
matroska	Add support for the matroska container format (extensions .mkv, .mka and .mks)
mbox	Add support for mbox (/var/spool/mail) style mail spools
memcached	Add support for memcached
memlimit	Add memory usage limiting in supporting programs
mhash	Add support for the mhash library
migemo	Enable migemo support for Japanese
mikmod	Add libmikmod support to allow playing of SoundTracker-style music files
milter	Add sendmail mail filter (milter) support
mime	Add MIME support
minimal	Install a very minimal build (disables, for example, plugins, fonts, most drivers, non-critical features)
mmap	Add mmap (memory map) support
mms	Support for Microsoft Media Server (MMS) streams
mng	Add support for libmng (MNG images)
modplug	Add libmodplug support for playing SoundTracker-style music files
modules	Build the kernel modules
mono	Build Mono bindings to support dotnet type stuff
motif	Add support for the Motif toolkit
mozilla	Add support for the Mozilla web-browser
mp3	Add support for reading mp3 files
mp4	Support for MP4 container format
mpeg	Add libmpeg3 support to various packages
mpi	Add MPI (Message Passing Interface) layer to the apps that support it
mplayer	Enable mplayer support for playback or encoding
msn	Enable MSN Messenger IM protocol support
mssql	Add support for Microsoft SQL Server database
mtp	Enable support for Media Transfer Protocol
mule	Add multi-language support to XEmacs
multilib	On 64bit systems, if you want to be able to compile 32bit and 64bit binaries
musepack	Enable support for the musepack audio codec
musicbrainz	Lookup audio metadata using MusicBrainz community service (musicbrainz.org)
mysql	Add mySQL Database support
mysqli	Add support for the improved mySQL libraries
nas	Add support for network audio sound
ncurses	Add ncurses support (console display library)
neXt	Enable neXt toolkit
neon	Enable optimization support for ARM NEON processors
netboot	Enable network booting
netcdf	Enable NetCDF data format support
networkmanager	Enable net-misc/networkmanager support
nis	Support for NIS/YP services
nls	Add Native Language Support (using gettext - GNU locale utilities)
nntp	Add support for newsgroups (Network News Transfer Protocol)
nocd	Install all files required to run the application without a CD mounted
nptl	Enable support for Native POSIX Threads Library, the new threading module (requires linux-2.6 or better usually)
nsplugin	Build plugin for browsers supporting the Netscape plugin architecture (that is almost any modern browser)
ocaml	Add support/bindings for the Ocaml language
ocamlopt	Enable ocamlopt support (ocaml native code compiler) -- Produces faster programs (Warning: you have to disable/enable it at a global scale)
oci8	Add Oracle 8 Database Support
oci8-instant-client	Use dev-db/oracle-instantclient-basic as Oracle provider instead of requiring a full Oracle server install
odbc	Add ODBC Support (Open DataBase Connectivity)
offensive	Enable potentially offensive items in packages
ofx	Enable support for importing (and exporting) OFX (Open Financial eXchange) data files
ogg	Add support for the Ogg container format (commonly used by Vorbis, Theora and flac)
openal	Add support for the Open Audio Library
openexr	Support for the OpenEXR graphics file format
opengl	Add support for OpenGL (3D graphics)
openmp	Build support for the OpenMP (support parallel computing), requires >=sys-devel/gcc-4.2 built with USE="openmp"
oracle	Enable Oracle Database support
orc	Use dev-lang/orc for just-in-time optimization of array operations
osc	Enable support for Open Sound Control
oscar	Enable Oscar (AIM/ICQ) IM protocol support
oss	Add support for OSS (Open Sound System)
pam	Add support for PAM (Pluggable Authentication Modules) - DANGEROUS to arbitrarily flip
pch	Enable precompiled header support for faster compilation at the expense of disk space and memory (>=sys-devel/gcc-3.4 only)
pcmcia	Add support for PCMCIA slots/devices found on laptop computers
pcntl	Add support for process creation functions
pcre	Add support for Perl Compatible Regular Expressions
pda	Add support for portable devices
pdf	Add general support for PDF (Portable Document Format), this replaces the pdflib and cpdflib flags
perl	Add optional support/bindings for the Perl language
php	Include support for the PHP language
pie	Build programs as Position Independent Executables (a security hardening technique)
plasma	Build optional KDE plasma addons
plotutils	Add support for plotutils (library for 2-D vector graphics)
png	Add support for libpng (PNG images)
policykit	Enable PolicyKit authentication support
portaudio	Add support for the crossplatform portaudio audio API
posix	Add support for POSIX-compatible functions
postgres	Add support for the postgresql database
postscript	Enable support for the PostScript language (often with ghostscript-gpl or libspectre)
ppds	Add support for automatically generated ppd (printing driver) files
prefix	Defines if a Gentoo Prefix offset installation is used
prelude	Add support/bindings for the Prelude Intrusion Detection System
profile	Add support for software performance analysis (will likely vary from ebuild to ebuild)
pulseaudio	Add support for PulseAudio sound server
python	Add optional support/bindings for the Python language
qdbm	Add support for the qdbm (Quick Database Manager) library
qmail-spp	Add support for qmail SMTP plugins
qt4	Add support for the Qt GUI/Application Toolkit version 4.x
qt5	Add support for the Qt 5 application and UI framework
quicktime	Add support for OpenQuickTime
radius	Add support for RADIUS authentication
raw	Add support for raw image formats
rdp	Enables RDP/Remote Desktop support
readline	Enable support for libreadline, a GNU line-editing library that almost everyone wants
recode	Enable support for the GNU recode library
rss	Enable support for RSS feeds
ruby	Add support/bindings for the Ruby language
samba	Add support for SAMBA (Windows File and Printer sharing)
sasl	Add support for the Simple Authentication and Security Layer
savedconfig	Use this to restore your config from /etc/portage/savedconfig ${CATEGORY}/${PN}. Make sure your USE flags allow for appropriate dependencies
scanner	Add support for scanner hardware (e.g. build the sane frontend in kdegraphics)
sctp	Support for Stream Control Transmission Protocol
sdl	Add support for Simple Direct Layer (media library)
seamonkey	Add support for the Seamonkey web-browser
seccomp	Enable seccomp (secure computing mode) to perform system call filtering at runtime to increase security of programs
selinux	!!internal use only!! Security Enhanced Linux support, this must be set by the selinux profile or breakage will occur
semantic-desktop	Cross-KDE support for semantic search and information retrieval
session	Add persistent session support
sharedmem	Add support for shared memory use
shorten	Add support for the shorten audio compressor
simplexml	Support for SimpleXML
skey	Enable S/Key (Single use password) authentication support
slang	Add support for the slang text display library (it's like ncurses, but different)
slp	Add Service Locator Protocol support
smartcard	Enable smartcard support
smp	Enable support for multiprocessors or multicore systems
sndfile	Add support for libsndfile
snmp	Add support for the Simple Network Management Protocol if available
soap	Add support for SOAP (Simple Object Access Protocol)
sockets	Add support for tcp/ip sockets
socks5	Add support for the socks5 proxy
sound	Enable sound support
source	Zip the sources and install them
sox	Add support for Sound eXchange (SoX)
speex	Add support for the speex audio codec (used for speech)
spell	Add dictionary support
sqlite	Add support for sqlite - embedded sql database
ssl	Add support for Secure Socket Layer connections
startup-notification	Enable application startup event feedback mechanism
static	!!do not set this during bootstrap!! Causes binaries to be statically linked instead of dynamically
static-libs	Build static versions of dynamic libraries as well
subversion	Enable subversion (version control system) support
suid	Enable setuid root program, with potential security risks
svg	Add support for SVG (Scalable Vector Graphics)
svga	Add support for SVGAlib (graphics library)
sybase	Add support for the Sybase SQL Database Server
sybase-ct	Add support for Sybase-CT
symlink	Force kernel ebuilds to automatically update the /usr/src/linux symlink
syslog	Enable support for syslog
systemd	Enable use of systemd-specific libraries and features like socket activation or session tracking
sysvipc	Support for System V-compatible inter-process communication
szip	Use the szip compression library
taglib	Enable tagging support with taglib
tcl	Add support the Tcl language
tcmalloc	Use the dev-util/google-perftools libraries to replace the malloc() implementation with a possibly faster one
tcpd	Add support for TCP wrappers
test	Workaround to pull in packages needed to run with FEATURES=test. Portage-2.1.2 handles this internally, so don't set it in make.conf/package.use anymore
theora	Add support for the Theora Video Compression Codec
threads	Add threads support for various packages. Usually pthreads
tidy	Add support for HTML Tidy
tiff	Add support for the TIFF image format
timidity	Build with Timidity++ (MIDI sequencer) support
tk	Add support for Tk GUI toolkit
tokenizer	Add support for the PHP file parser
truetype	Add support for FreeType and/or FreeType2 fonts
uclibc	Enable uclibc specific patches and build or link uclibc
udev	Enable virtual/udev integration (device discovery, power and storage device support, etc)
udisks	Enable storage management support (automounting, volume monitoring, etc)
unicode	Add support for Unicode
unwind	Add support for call stack unwinding and function name resolution
upnp	Enable UPnP port mapping support
upnp-av	Enable UPnP audio/video streaming support
upower	Enable power management support
usb	Add USB support to applications that have optional USB support (e.g. cups)
v4l	Enable support for video4linux (using linux-headers or userspace libv4l libraries)
vaapi	Enable Video Acceleration API for hardware decoding
vala	Enable bindings for dev-lang/vala
vanilla	Do not add extra patches which change default behaviour; DO NOT USE THIS ON A GLOBAL SCALE as the severity of the meaning changes drastically
vcd	Video CD support
vdpau	Enable the Video Decode and Presentation API for Unix acceleration interface
vhosts	Add support for installing web-based applications into a virtual-hosting environment
videos	Install optional video files (used in some games)
vim-syntax	Pulls in related vim syntax scripts
vnc	Enable VNC (remote desktop viewer) support
vorbis	Add support for the OggVorbis audio codec
wayland	Enable dev-libs/wayland backend
wavpack	Add support for wavpack audio compression tools
wddx	Add support for Web Distributed Data eXchange
webkit	Add support for the WebKit HTML rendering/layout engine
webp	Add support for the WebP image format
wifi	Enable wireless network functions
wmf	Add support for the Windows Metafile vector image format
wxwidgets	Add support for wxWidgets/wxGTK GUI toolkit
x264	Enable h264 encoding using x264
xattr	Add support for extended attributes (filesystem-stored metadata)
xcb	Support the X C-language Binding, a replacement for Xlib
xcomposite	Enable support for the Xorg composite extension
xemacs	Add support for XEmacs
xface	Add xface support used to allow a small image of xface format to be included in an email via the header 'X-Face'
xft	Build with support for XFT font renderer (x11-libs/libXft)
xine	Add support for the XINE movie libraries
xinerama	Add support for the xinerama X11 extension, which is mandatory if you work in multiple monitors setup
xinetd	Add support for the xinetd super-server
xml	Add support for XML files
xmlrpc	Support for xml-rpc library
xmp	Enable support for Extensible Metadata Platform (Adobe XMP)
xmpp	Enable support for Extensible Messaging and Presence Protocol (XMPP) formerly known as Jabber
xosd	Sends display using the X On Screen Display library
xpm	Add support for XPM graphics format
xscreensaver	Add support for XScreenSaver extension
xv	Add in optional support for the Xvideo extension (an X API for video playback)
xvid	Add support for xvid.org's open-source mpeg-4 codec
yahoo	Enable Yahoo Messenger IM protocol support
yaz	Add in optional support for the Z39.50 Protocol for Information Retrieval (YAZ)
zeroconf	Support for DNS Service Discovery (DNS-SD)
zlib	Add support for zlib (de)compression
zsh-completion	Enable zsh completion support

Local USE Flags

app-accessibility

brltty

api	build brltty's application program interface
beeper	support the console tone generator
contracted-braille	support in-line contracted braille
fm	support for the sound card synthesizer
midi	support the musical instrument digital interface
pcm	support for sound card digital audio
speech	speech support

eflite

16k_voice	Use a higher-quality voice.

emacspeak

espeak	Adds support for the espeak tts engine

festival-it

mbrola	Adds support for mbrola voices

freetts

jsapi	build Java Speech API (JSAPI)
mbrola	Adds support for mbrola voices

orca

braille	Enable braille support

simon

opencv	Use media-libs/opencv
pim	Use kde-apps/kdepimlibs
sphinx	Build sphinx backend (pulls app-accessibility/julius if disabled

speech-dispatcher

espeak	Adds support for espeak speech engine
flite	Adds support for flite speech engine

speechd-el

brltty	brltty support

app-admin

bcfg2

cheetah	Include dev-python/cheetah support
genshi	Include dev-python/genshi support
server	Installs scripts to be used on the server-side of this app

calamares

pythonqt	Enable PythonQt-based module interface

clsync

cgroups	Use cgroups to limit /dev access.
cluster	Enable clustering support (allows master-master clsync on multiple hosts). Not fully implemented yet.
control-socket	Enable AF_UNIX control socket support.
extra-debug	Enable extra debugging. This will hurt performance badly. Be ready for tons of output.
extra-hardened	Enable extra security checks. This will hurt performance.
gio	Enable GIO for FS monitoring (glib based alternative to inotify interface, not recommended; if both are compiled, may be selected at runtime).
highload-locks	Allows to use spinlocks for short delays instead of mutexes, but only on SMP systems.
namespaces	Enable namespaces isolation.

collectd

contrib	Install user-contributed files in the doc directory
filecaps	When set collectd daemon will have set required capabilities to run most plugins even if run as unprivileged user
java	Must be set (workaround for java-pkg-opt-2 eclass limitation) when you want java or genericjmx plugin
udev	Enable optional udev usage in disk plugin; Required for smart plugin
xfs	Enable optional capability to filter on XFS file system in df plugin; Requires XFS headers from sys-fs/xfsprogs

conky

apcupsd	Enable support for sys-power/apcupsd
audacious	Enable monitoring of music played by media-sound/audacious
cmus	Enable monitoring of music played by media-sound/cmus
eve	Enable support for the eve-online skill monitor
ical	Enable support for events from iCalendar (RFC 5545) files using dev-libs/libical
iostats	Enable support for per-task I/O statistics
irc	Enable support for displaying everything from an irc channel using net-libs/libircclient
lua-cairo	Enable if you want Lua Cairo bindings
lua-imlib	Enable if you want Lua Imlib2 bindings
lua-rsvg	Enable if you want Lua RSVG bindings
math	Enable support for glibc's libm math library
moc	Enable monitoring of music played by media-sound/moc
mpd	Enable monitoring of music controlled by media-sound/mpd
nano-syntax	Enable syntax highlighting for app-editors/nano
nvidia	Enable reading of nvidia card temperature sensors via media-video/nvidia-settings
portmon	Enable support for tcp (ip4) port monitoring
thinkpad	Enable support for IBM/Lenovo notebooks
weather-metar	Enable support for metar weather service
weather-xoap	Enable support for metar and xoap weather service
webserver	Enable support to act as a webserver serving conkys output using net-libs/libmicrohttpd
xmms2	Enable monitoring of music played by media-sound/xmms2

diamond

mongo	Enable MongoDB support
redis	Enable Redis support

diradm

automount	Support for automount data in LDAP
irixpasswd	Support for storing separate IRIX passwords

elektra

augeas	Enable plugin for reading and writing configuration files with help from Augeas
ini	Enable new, advanced ini support
simpleini	Enable simpleini support
uname	Enable uname information for the key database
yajl	Enable yajl support

gkrellm

X	Build both the X11 gui (gkrellm) and the server (gkrellmd). Disabling this flag builds the server only.
gnutls	Enable SSL support for mail checking with net-libs/gnutls (overrides 'ssl' USE flag)
hddtemp	Enable monitoring harddrive temperatures via app-admin/hddtemp
lm_sensors	Enable monitoring sensors via sys-apps/lm_sensors
ntlm	Enable NTLM authentication for mail checking with net-libs/libntlm
ssl	Enable SSL support for mail checking with dev-libs/openssl

glance

swift	Adds swift storage support

gtkdiskfree

gtk2	Support GTK+ 2.x instead of GTK+ 3.x

hddtemp

network-cron	Monthly cronjob to update hddtemp.db.

keepass

aot	Generate native code at build time, rather than runtime.

keepassxc

autotype	Add support to autotype the passwords into other applications
http	Add http support

lastpass-cli

X	Use x11-misc/xclip or x11-misc/xsel to copy passwords to the clipboard.
pinentry	Use app-crypt/pinentry to prompt for passwords.

logrotate

acl	Installs acl support
cron	Installs cron file
selinux	Installs Security Enhanced Linux support

matter

entropy	Add Entropy support

mcollective

client	Install client utilities

mms-agent

monitoring	Install the monitoring agent

openrc-settingsd

systemd	Use the versions of dbus and polkit files provided by sys-apps/systemd

packagekit-base

command-not-found	Enable packagekit support on shell "command not found"
cron	Install cron script for auto-update
elogind	Enable elogind support to get user session
entropy	Enable Entropy backend

pass

X	Use x11-misc/xclip to copy passwords to the clipboard.
dmenu	Add support for x11-misc/dmenu with the 'passmenu' program.
fish-completion	Enable fish completion support.
git	Use dev-vcs/git for password revisions.
importers	Allow importing passwords from other password managers using various contributed scripts.

passwordsafe

minimal	Avoid collision with app-misc/pwsafe
xml	Enable XML import support
yubikey	Enable support for Yubikey

prelude-manager

dbx	Enables Prelude Manager storing Prelude alerts into database through dev-libs/libpreludedb .
tcpwrapper	Enables Prelude Manager using tcp wrapper. It requires sys-apps/tcp-wrappers .

puppet

augeas	Enable augeas support
diff	Enable diff support
experimental	Add patches for things in testing
rrdtool	Enable rrdtool support
shadow	Enable shadow support

puppet-agent

experimental	Add patches for things in testing
puppetdb	Adds puppetdb support

puppetserver

puppetdb	Adds support for connecting to puppetdb

pwgen

livecd	Install init script for root password scrambling on boot

rsyslog

dbi	Build the general database output module (requires dev-db/libdbi)
elasticsearch	Build the Elasticsearch output module (requires net-misc/curl)
gcrypt	Add support for encrypted log files using dev-libs/libgcrypt
grok	Build the grok modify module (requires dev-libs/grok)
jemalloc	Use dev-libs/jemalloc for allocations.
kafka	Build the Apache Kafka input/output module (requires dev-libs/librdkafka)
kerberos	Build the GSSAPI input and output module (requires virtual/krb5)
libressl	Use dev-libs/libressl for building the rfc5424hmac modify module (requires rfc5424hmac USE flag)
mdblookup	Build the MaxMind DB lookup message modify plugin using dev-libs/libmaxminddb
mongodb	Build the MongoDB output module (requires dev-libs/libmongo-client)
mysql	Build the MySQL database output module (requires virtual/mysql)
normalize	Build the normalize modify module (requires dev-libs/libee and dev-libs/liblognorm)
omhttpfs	Build the httpfs output module (requires net-misc/curl)
omudpspoof	Build the udpspoof output module (requires net-libs/libnet)
postgres	Build the PostgreSQL database output module (requires dev-db/postgresql)
rabbitmq	Build the RabbitMQ output module (requires net-libs/rabbitmq-c)
redis	Build the Redis output module using (requires dev-libs/hiredis)
relp	Build the Reliable Event Logging Protocol (RELP) output module (requires dev-libs/librelp)
rfc3195	Build the rfc3195 input module (requires dev-libs/liblogging)
rfc5424hmac	Build the rfc5424hmac modify module (requires dev-libs/openssl or dev-libs/libressl)
snmp	Build the snmp modify and output module (requires net-analyzer/net-snmp)
ssl	Add support for encrypted client/server communication (requires net-libs/gnutls)
systemd	Build the journal input and output module (requires sys-apps/systemd)
usertools	Installs the user tools (rsgtutil, rscryutil...) corresponding to the set USE flags
uuid	Include UUIDs in messages (requires sys-apps/util-linux)
zeromq	Build the ZeroMQ input and output modules (requires net-libs/czmq)

sagan

libdnet	Add support for dev-libs/libdnet
lognorm	Add support for log/rules normalizations via dev-libs/liblognorm
pcap	Add support for network packet capture via net-libs/libpcap
smtp	Build witch SMTP (E-Mail) support
snort	Add support to interact with Snort IDE using net-analyzer/snortsam'

sagan-rules

lognorm	Install normalize rules support with dev-libs/liblognorm

salt

cherrypy	Enable support for using cherrypy.
gnupg	Enable support for gnupg via python-gnupg.
keyring	Enable support for keyrings via python-keyring.
libcloud	Enable salt-cloud support via libcloud.
libvirt	Support managing virtual machines with app-emulation/libvirt.
mako	Add support for using the mako template engine for parsing salt states.
mongodb	Support returning data to a mongodb server.
neutron	Support the OpenStack neutron network service.
nova	Enable support for the OpenStack Nova API
openssl	Add support for using TLS via OpenSSL.
portage	Add support for package state enforcement using sys-apps/portage
raet	Add support for the new RAET transport.
redis	Support returning data to a redis database.
timelib	Use timelib to parse english textual date descriptions.
zeromq	Add support for the zeromq transport.

sshguard

ipfilter	Enable ipfilter firewall support (only for *bsd)

sudo

gcrypt	Use SHA2 from dev-libs/libgcrypt instead of sudo's internal SHA2.
offensive	Let sudo print insults when the user types the wrong password.
openssl	Use SHA2 from dev-libs/openssl instead of sudo's internal SHA2.
sendmail	Allow sudo to send emails with sendmail.

sysklogd

logrotate	use app-admin/logrotate for rotating logs rather than custom cron scripts

syslog-ng

amqp	Enable support for AMQP destinations
json	Enable support for JSON template formatting via dev-libs/json-c
mongodb	Enable support for mongodb destinations
pacct	Enable support for reading Process Accounting files (EXPERIMENTAL, Linux only)
redis	Enable support for Redis destinations
smtp	Enable support for SMTP destinations
spoof-source	Enable support for spoofed source addresses

sysstat

isag	Install isag, the Interactive System Activity Graph tool

systemrescuecd-x86

isohybrid	Pass downloaded images through isohybrid in order to make it possible to copy them directly to USB media and boot (requires sys-boot/syslinux at build time).

testdisk

ewf	Include ewf library
ntfs	Include the ability to read NTFS filesystems
reiserfs	Include reiserfs reading ability

tripwire

ssl	Adds support for Secure Socket Layer connections
static	Builds the package statically
tools	Installs app-admin/mktwpol, providing scripts for the installation/setup of tripwire, including generating the tripwire policy file and maintenance of the tripwire database

ulogd

json	Build JSON output plugin to save packets in JSON file format
nfacct	Build NFACCT input plugin to support traffic accounting via nfnetlink_acct
nfct	Build NFCT input plugin to support stateful flow-based logging via nfnetlink_conntrack
nflog	Build NFLOG input plugin to support stateless packet-based logging via nfnetlink_log
pcap	Build PCAP output plugin to save packets in libpcap file format
ulog	Build ULOG input plugin to support deprecated packet-based logging via ULOG target

webalizer

xtended	Include the 404 extension

webapp-config

portage	Propagete python_targets dependencies to sys-apps/portage

yaala

storable	Support for persistence of Perl data structures.

app-antivirus

clamav

clamdtop	A Top like tool which shows what clamd is currently scanning amongst other things
metadata-analysis-api	Enables collection of file property metadata using ClamAV API for analysis by ClamAV bytecode programs.

app-arch

cabextract

extras	Install experimental extra tools: wince_info and wince_rename for examining and processing Windows CE installation cabinet header files; cabinfo for examining the structure of a cab file.

cfv

bittorrent	Enable support for checking .torrent files

deltarpm

system-zlib	Use system sys-libs/zlib. Do not enable features of rsync friendly.

dpkg

update-alternatives	Install update-alternatives

dump

ermt	encrypted rmt support
uuid	Enable UUID support

engrampa

caja	Enable engrampa to integrate with mate-base/caja by providing entries in its context menu
gtk3	Build with GTK+3 instead of GTK+2
magic	Enable filetype auto-detection via sys-apps/file
packagekit	Enable support for installing via app-admin/packagekit based on archive type

file-roller

packagekit	Enable support for the distro-neutral package manager GUI app-admin/packagekit

gzip

pic	disable optimized assembly code that is not PIC friendly

innoextract

c++0x	Compile innoextract using the C++11 standard.
debug	Enable debug logging and the --debug command-line option.
lzma	Enable support for extracting lzma-compressed installers using app-arch/xz-utils.

libarchive

bzip2	Allow accessing bzip2-compressed archives through libbz2 (which comes with app-arch/bzip2). This only affects libarchive's native support: bsdtar will keep using bunzip2 as a filter if that's not built-in.
e2fsprogs	Use file flags from sys-fs/e2fsprogs headers instead of virtual/os-headers headers
lz4	Enable support for LZ4 compression using app-arch/lz4
nettle	Use dev-libs/nettle as crypto backend
zlib	Allow accessing gzip-compressed archives through sys-libs/zlib. This only affects libarchive's native support: bsdtar will keep using gunzip as a filter if that's not built-in. It's also needed for supporting extraction of ZIP files.

lz4

valgrind	Enable usage of dev-util/valgrind in tests

p7zip

rar	Enable support for non-free rar decoder

pbzip2

symlink	Install symlinks which override app-arch/bzip2 implementation

pigz

symlink	Install symlinks which override app-arch/gzip implementation

rar

all_sfx	Install all SFX (Self-Extracting) files rather than just the native format (allows creation of Windows EXEs on Linux ELF systems)

tar

minimal	just install `tar`

unzip

natspec	Use dev-libs/libnatspec to correctly decode non-ascii file names archived in Windows.

zip

natspec	Use dev-libs/libnatspec to correctly decode non-ascii file names archived in Windows.

app-backup

amanda

s3	Support for backing up to the Amazon S3 system
xfs	Support for backing up raw XFS filesystems using xfsdump

backup-manager

s3	Support for backing up to the Amazon S3 system

bacula

bacula-clientonly	Disable DB support, and just build a client
bacula-nodir	Disable building of director
bacula-nosd	Disable building of storage daemon
logwatch	Install support files for logwatch

bareos

cephfs	Enable cephfs storage backend
clientonly	Only install file-daemon (client)
director	Install director
fastlz	Enable support vor lz4, lz4hc and lzfast using dev-libs/bareos-fastlzlib
glusterfs	Enable glusterfs storage backend
gnutls	When ssl is enabled, use GnuTLS instead of OpenSSL
jansson	JSON API support using JANSSON for director
lmdb	enable build of LMDB support for faster accurate backup
logwatch	Install support files for logwatch
ndmp	Enable support for NDMP (Network Data Management Protocol)
rados	Enable rados storage backend
rados-striper	Enable use of rados-striper
scsi-crypto	Enable low level SCSI crypto support
sql-pooling	Enable SQL pooling support
storage-daemon	Install storage daemon (bareos-sd)

borgbackup

fuse	Mount archive as a FUSE filesystem.

boxbackup

client-only	Disable server support, and just build a client

btrbk

pv	Use sys-apps/pv to enable progress bar functionality

bup

web	Support browsing backups via a web interface

dar

dar32	Enables --enable-mode=32 option, which replace infinite by 32 bit integers
dar64	Enables --enable-mode=64 option, which replace infinite by 64 bit integers
gcrypt	Enables strong encryption support
gpg	Enables usage of asymetric crypto algorithms

deja-dup

nautilus	Build gnome-base/nautilus extension

duplicity

s3	Support for backing up to the Amazon S3 system

holland-backup-mysql-meta

lvm	Install Holland LVM Plugin
mysqldump	Install Holland mysqldump Plugin
mysqlhotcopy	Install Holland mysqlhotcopy Plugin

rear

udev	Have ReaR start backup when attaching your USB drive.

snapper

btrfs	Include Btrfs support sys-fs/btrfs-progs
ext4	Include Ext4 support sys-fs/e2fsprogs
lvm	Enable LVM thinprovisioned snapshots support sys-fs/lvm2
xattr	Add support for getting and setting POSIX extended attributes, through sys-apps/attr.

tsm

tsm_cit	IBM Tivoli Common Inventory Technology
tsm_hw	Difference snapshot support for NetApp and N-Series file servers

zbackup

tartool	Install tartool utility

app-benchmarks

filebench

auto-completion	Enable command-line autocompletion using dev-libs/libtecla.

httperf

idleconn	Build with the idleconn program

jmeter

beanshell	Enable BeanShell scripting support

ramspeed

pic	Force shared libraries to be built as PIC (this is slower)

sysbench

aio	Enable libaio support

app-cdr

brasero

libburn	Enable dev-libs/libburn backend
nautilus	Build the gnome-base/nautilus extension
packagekit	Enable support for the distro-neutral package manager GUI app-admin/packagekit
playlist	Enable support for playlists through dev-libs/totem-pl-parser
tracker	Enable audio playlist search using the app-misc/tracker indexer

cdemu

cdemu-daemon	Pull app-cdr/cdemu-daemon dependency, useful in chroot environment (bug #315491). Do not disable until you know what you are doing.

cdrdao

gcdmaster	Enable building of gcdmaster application

cdrkit

hfs	Provide building of HFS (Apple) CD-images

cuetools

extras	Install additional script that tag files based on cue/toc file information

dvdisaster

debug	Enable memory debugging.

gaffitter

scripts	Install additional gaffitter scripts for external programs

mirage2iso

pinentry	Support app-crypt/pinentry password input backend.

app-crypt

aespipe

asm	Enable assembly modules
cpu_flags_x86_padlock	Use VIA padlock instructions, detected at run time, code still works on non-padlock processors

ccid

kobil-midentity	Build and install Kobil_mIDentity_switch tool
twinserial	Enable twinserial reader

codecrypt

cryptopp	Build algorithms that need Crypto++ support dev-libs/crypto++

eid-mw

dialogs	Enable "askaccess" dialog box, by using x11-libs/gtk+
gtk	All dialogs are available, by using x11-libs/gtk+
p11-kit	Support for app-crypt/p11-kit.
xpi	Build and install an extension for Mozilla browsers.

ekeyd

minimal	Only install the ekey-egd-linux service rather than the full ekeyd package.
munin	Install a plugin for net-analyzer/munin to graph statistical data from ekeyd.
usb	Build the libusb-based userland daemon for accessing the EntropyKey (alternative to the CDC USB driver). It is suggested to use this option by default, as the CDC driver in the kernel often seems to be fragile (or the gadget implementation on the EntropyKey is too buggy), and can cause various problems.

gnupg

mta	Build mta support using virtual/mta.
smartcard	Build scdaemon software. Enables usage of OpenPGP cards. For other type of smartcards, try app-crypt/gnupg-pkcs11-scd. Bring in dev-libs/libusb as a dependency; enable scdaemon.
tofu	Enable support for Trust of First use trust model; requires dev-db/sqlite.
tools	Install extra tools (including gpgsplit and gpg-zip).
usb	Build direct CCID access for scdaemon; requires dev-libs/libusb.
wks-server	Install the wks-server

gpgme

common-lisp	Install common-lisp files

heimdal

hdb-ldap	Adds support for LDAP as a database backend
otp	Adds support for one-time passwords
pkinit	Adds support for PKINIT for the initial ticket

hmaccalc

fips	Enable NSS FIPS mode and support only the FIPS-compliant functions

johntheripper

cuda	Use nvidia cuda toolkit for speeding up cracking on capable devices
mozilla	Support mozilla password cracking
opencl	Enable opencl support for speeding up cracking on capable devices

kstart

afs	Enables afs support which means you can acquire an afs token and set PAGs. It's recommended to set this USE if you need authenticated access to an AFS cell for your daemon/app.

libu2f-host

systemd	Use user ACLs rather than plugdev group to give user access to the HIDRAW device.

mit-krb5

doc	Creates and installs the API and implementation documentation. This is only useful if you want to develop software which depends on kerberos.
keyutils	Enable for the keyring ccache using keyutils.
openldap	Enable support for ldap as a database backend.
pkinit	Enable pkinit support for the initial ticket.

ophcrack

tables	Require the additional tables used to carry out cracking (app-crypt/ophcrack-tables)

ophcrack-tables

vistafree	Installs the free Vista ophcrack tables
xpfast	Installs the fast XP ophcrack tables
xpsmall	Installs the small free XP ophcrack tables

p11-kit

asn1	Enable ASN.1 certificate support
trust	Build the trust policy module

qca

botan	Enable botan plugin
gcrypt	Enable gcrypt plugin
gpg	Enable GnuPG plugin
logger	Enable logger plugin
nss	Enable NSS plugin
pkcs11	Enable PKCS#11 plugin
sasl	Enable SASL plugin
softstore	Enable softstore plugin

rhash

openssl	Add support for hashes from dev-libs/openssl

seahorse

ldap	Enable seahorse to manipulate GPG keys on a LDAP server.

tpm-tools

pkcs11	Build Token data management utilities based on OpenCryptoki's (dev-libs/opencryptoki) PKCS#11 implementation.

veracrypt

asm	Enable assembly for optimization

zuluCrypt

gnome	Enable support for the freedesktop.org Secret Service API via app-crypt/libsecret
kwallet	Enable encrypted storage of passwords with kde-frameworks/kwallet
udev	Whether udev will be consulted when deciding if a volume is system or not

app-dicts

aspell-be

classic	Support classic spelling by default

gwaei

hunspell	Enable app-text/hunspell spellchecking and morphological analysis
mecab	Enable app-text/mecab support

myspell-pt

preao	Use the pre ortographic agreement version of the dictionary

app-doc

clsync-docs

api	Install doxygen generated API docs.

csound-manual

html	Install HTML documentation

doxygen

clang	support for sys-devel/clang assisted parsing
dot	allow to create dot graphs using media-gfx/graphviz
doxysearch	build doxyindexer and doxysearch.cgi

kicad-doc

html	Generate documentation in HTML format
pdf	Generate documentation in PDF format

linuxfromscratch

htmlsingle	Install all-on-one-page HTML version.

pms

binary	Download pre-built files instead of building from sources
html	Generate PMS as .html as well
twoside	Enable two-sided layout suitable for printing

root-docs

api	Generate html API documentation
http	Build HttpServer documentation
math	Provide all math related documentation
metric	Default to A4 paper size and metric measurement. Letter will be used otherwise

tldp-howto

html	Install multi-chapter HTML docs
htmlsingle	Install all-on-one-page HTML docs
pdf	Install pdf docs
text	Install plain-text docs

app-editors

bluefish

gtk2	Enable GTK2 instead of GTK3 even if GTK3 is available
gtk3	Enable GTK3 interface (default)
gucharmap	Enable gucharmap dictionary plugin
python	Enable Python integration for zen-coding plugin
spell	Enable spell checking capabilities via enchant library

emacs

athena	Enable the MIT Athena widget set (x11-libs/libXaw)
dynamic-loading	Enable loading of dynamic libraries at runtime
games	Support shared score files for games
gconf	Use gnome-base/gconf to read the system font name
gfile	Use gfile (dev-libs/glib) for file notification
gsettings	Use gsettings (dev-libs/glib) to read the system font name
gtk3	Prefer version 3 of the GIMP Toolkit to version 2 (x11-libs/gtk+)
gzip-el	Compress bundled Emacs Lisp source
hesiod	Enable support for net-dns/hesiod
imagemagick	Use media-gfx/imagemagick for image processing
libxml2	Use dev-libs/libxml2 to parse XML instead of the internal Lisp implementations
pax_kernel	Enable building under a PaX enabled kernel
source	Install C source files and make them available for find-function
toolkit-scroll-bars	Use the selected toolkit's scrollbars in preference to Emacs' own scrollbars
wide-int	Prefer wide Emacs integers (typically 62-bit). This option has an effect only on architectures where "long" and "long long" types have different size.
xwidgets	Enable use of GTK widgets in Emacs buffers (requires GTK3)

emacs-vcs

athena	Enable the MIT Athena widget set (x11-libs/libXaw)
dynamic-loading	Enable loading of dynamic libraries at runtime
games	Support shared score files for games
gconf	Use gnome-base/gconf to read the system font name
gfile	Use gfile (dev-libs/glib) for file notification
gsettings	Use gsettings (dev-libs/glib) to read the system font name
gtk3	Prefer version 3 of the GIMP Toolkit to version 2 (x11-libs/gtk+)
gzip-el	Compress bundled Emacs Lisp source
hesiod	Enable support for net-dns/hesiod
imagemagick	Use media-gfx/imagemagick for image processing
libxml2	Use dev-libs/libxml2 to parse XML instead of the internal Lisp implementations
mailutils	Retrieve e-mail using net-mail/mailutils instead of the internal movemail substitute
pax_kernel	Enable building under a PaX enabled kernel
source	Install C source files and make them available for find-function
threads	Add elisp threading support
toolkit-scroll-bars	Use the selected toolkit's scrollbars in preference to Emacs' own scrollbars
wide-int	Prefer wide Emacs integers (typically 62-bit). This option has an effect only on architectures where "long" and "long long" types have different size.
xwidgets	Enable use of GTK widgets in Emacs buffers (requires GTK3)

fe

sendmail	Send mail after editor abend

gedit-plugins

charmap	Insert special characters just by clicking on them
git	Shows document changes related to git's HEAD
terminal	Embed a terminal in the bottom pane
zeitgeist	Build the plugin to inject events to gnome-extra/zeitgeist

gvim

gtk3	Enable GTK+3 interface
luajit	Use dev-lang/luajit instead of dev-lang/lua
netbeans	Include netbeans external editor integration support
racket	Enable support for Scheme using dev-scheme/racket

jasspa-microemacs

nanoemacs	Build NanoEmacs instead of MicroEmacs

joe

xterm	Enable full xterm clipboard support

latexila

latexmk	Install dev-tex/latexmk (used by default for the build tools)
rubber	Install dev-tex/rubber (can be used for the build tools)

leafpad

emacs	Enable Emacs key theme

mousepad

gtk3	Use GTK+3 instead of GTK+2

nano

debug	Enable debug messages and assert warnings. Note that these will all be sent straight to stderr rather than some logging facility.
justify	Enable justify/unjustify functions for text formatting.
magic	Add magic file support (sys-apps/file) to automatically detect appropriate syntax highlighting
minimal	Disable all fancy features, including ones that otherwise have a dedicated USE flag (such as spelling).

ne

tinfo	Link against libtinfo from sys-libs/ncurses

neovim

clipboard	Enable clipboard support through a provider
jemalloc	Use dev-libs/jemalloc for allocations
luajit	Use dev-lang/luajit instead of dev-lang/lua
nvimpager	Install nvimpager symlink to less.sh macro
tui	Build the neovim unix tui

pluma

gtk3	Build with GTK+3 instead of GTK+2

tea

aspell	Enable spellchecking using app-text/aspell
hunspell	Enable spellchecking using app-text/hunspell

vim

X	Link console vim against X11 libraries to enable title and clipboard features in xterm
luajit	Use dev-lang/luajit instead of dev-lang/lua
racket	Enable support for Scheme using dev-scheme/racket
vim-pager	Install vimpager and vimmanpager links

vis

tre	more memory efficient regex search using dev-libs/tre

xemacs

athena	Chooses the MIT Athena widget set
dnd	Enables support for the x11-libs/dnd drag-n-drop library
eolconv	Support detection and translation of newline conventions
pop	Support POP for mail retrieval
xim	Enable X11 XiM input method

zile

valgrind	Enable usage of dev-util/valgrind in tests

app-emacs

anything

extensions	Install optional extensions

auctex

preview-latex	Use bundled preview-latex

bbdb

tex	Install plain TeX support files
vm	Add support for app-emacs/vm

calfw

howm	Add support for the app-emacs/howm note-taking tool

company-mode

ropemacs	Install backend for dev-python/ropemacs

emacs-common-gentoo

games	Support shared score files for games

emhacks

jde	Enable support for Java Development Environment

magit

contrib	Install user-contributed files

org-mode

contrib	Install user-contributed files
odt-schema	Install non-free schema files for OpenDocument Text exporter

remember

bbdb	Include support for app-emacs/bbdb
planner	Include support for app-emacs/planner

slime

xref	Install xref.lisp cross-referencing tool

vm

bbdb	Include support for app-emacs/bbdb

wanderlust

bbdb	Include support for app-emacs/bbdb

wikipedia-mode

outline-magic	Enable support for outline-mode extensions (app-emacs/outline-magic)

app-emulation

bochs

3dnow	Enable support for emulating 3DNow! instructions (incomplete)
avx	Enable support for emulating Advanced Vector Extensions (AVX)
debugger	Enable debugger (slows down emulation)
gdb	Enable support for the remote GDB stub
x86-64	Enable support for emulation of 64-bit CPUs

crossover-bin

capi	Enable ISDN support via CAPI

docker

apparmor	Enable AppArmor support.
aufs	Enables dependencies for the "aufs" graph driver, including necessary kernel flags.
btrfs	Enables dependencies for the "btrfs" graph driver, including necessary kernel flags.
container-init	Makes the a staticly-linked init system tini available inside a container.
device-mapper	Enables dependencies for the "devicemapper" graph driver, including necessary kernel flags.
experimental	Enable features labelled by upstream to be of "experimental" quality and not yet ready for general consumption.
overlay	Enables dependencies for the "overlay" graph driver, including necessary kernel flags.
pkcs11	Enables pkcs-11 support.

docker-runc

apparmor	Enable AppArmor support.

dosemu

fluidsynth	use media-sound/fluidsynth for MIDI emulation

e-uae

capslib	Add CAPS library support
sdl-sound	Use media-libs/sdl-sound for audio output

free42

alsa	Adds support for Advanced Linux Sound Architecture

fuse-utils

gcrypt	Use dev-libs/libgcrypt for low-level crypto of some features, including logfiles.

ganeti

drbd	Enable DRBD support
experimental	Enable experimental patches. Warning! This will break RPC within major versions if the patches applied differ!
haskell-daemons	Build haskell daemons instead of python
htools	Enable htools support
kvm	Enable KVM support
lxc	Enable Linux Countainers support
monitoring	Enable the ganeti monitoring daemon
multiple-users	Enable support for running VMs as different users
rbd	Enable rados block device support via sys-cluster/ceph
restricted-commands	Enable restricted commands in the node daemon
xen	Enable Xen support

hyperd

libvirt	Enable support for KVM via libvirt
xen	Enable support for the Xen Hypervisor

libguestfs

erlang	Build Erlang bindings
fuse	Enable image mount support via fuse
inspect-icons	Use media-gfx/icoutilsfor acces icon file in image and inspect it
systemtap	Use dev-util/systemtap to inspect VM via "probes" way

libspectrum

gcrypt	Use dev-libs/libgcrypt for low-level crypto of some features, including logfiles.

libvirt

apparmor	Enable AppArmor support
firewalld	DBus interface to iptables/ebtables allowing for better runtime management of your firewall.
fuse	Allow LXC to use sys-fs/fuse for mount points
glusterfs	Enable GlusterFS support via sys-cluster/glusterfs
iscsi	Allow using an iSCSI remote storage server as pool for disk image storage
libssh	Use net-libs/libssh to communicate with remote libvirtd hosts, for example: qemu+libssh://server/system
libvirtd	Builds the libvirtd daemon as well as the client utilities instead of just the client utilities
lvm	Allow using the Logical Volume Manager (sys-fs/lvm2) as pool for disk image storage
lxc	Support management of Linux Containers virtualisation (app-emulation/lxc)
macvtap	Support for MAC-based TAP (macvlan/macvtap). For networking instead of the normal TUN/TAP. It has its advantages and disadvantages. macvtap support requires very new kernels and is currently evolving. Support for this is experimental at best.
nfs	Allow using Network File System mounts as pool for disk image storage
numa	Use NUMA for memory segmenting via sys-process/numactl and sys-process/numad
openvz	Support management of OpenVZ virtualisation (see sys-kernel/openvz-sources)
parted	Allow using real disk partitions as pool for disk image storage, using sys-block/parted to create, resize and delete them.
pcap	Support auto learning IP addreses for routing
phyp	Support IBM HMC / IVM hypervisor via PHYP protocol
qemu	Support management of QEMU virtualisation (app-emulation/qemu)
rbd	Enable rados block device support via sys-cluster/ceph
uml	Support management of User Mode Linux virtualisation
vepa	Virtual Ethernet Port Aggregator (VEPA) / 802.1Qbg support. Relies on macvtap support.
virt-network	Enable virtual networking (NAT) support for guests. Includes all the dependencies for NATed network mode. Effectively any network setup that relies on libvirt to setup and configure network interfaces on your host. This can include bridged and routed networks ONLY if you are allowing libvirt to create and manage the underlying devices for you. In some cases this requires enabling the 'netcf' USE flag (currently unavailable).
virtualbox	Support management of VirtualBox virtualisation (one of app-emulation/virtualbox or app-emulation/virtualbox-bin)
wireshark-plugins	Build the net-analyzer/wireshark plugin for the Libvirt RPC protocol
xen	Support management of Xen virtualisation (app-emulation/xen)
zfs	Enable ZFS backend storage sys-fs/zfs

lxc

cgmanager	Enable support for cgroup management using app-admin/cgmanager

lxd

daemon	Build the system daemon, not just the client tool

open-vm-tools

doc	Generate API documentation
grabbitmqproxy	Enable grabbitmqproxy
pic	Force shared libraries to be built as PIC
vgauth	Enable vgauth

playonlinux

winbind	Enables support for the winbind auth daemon

q4wine

ico	Enable ico support via media-gfx/icoutils
iso	Support unprivileged mounting of ISO9660 images via sys-fs/fuseiso
wineappdb	Enable Wine AppDB browser support

qemu

accessibility	Adds support for braille displays using brltty
aio	Enables support for Linux's Async IO
alsa	Enable alsa output for sound emulation
curl	Support ISOs / -cdrom directives vis HTTP or HTTPS.
fdt	Enables firmware device tree support
glusterfs	Enables GlusterFS cluster fileystem via sys-cluster/glusterfs
gnutls	Enable TLS support for the VNC console server. For 1.4 and newer this also enables WebSocket support. For 2.0 through 2.3 also enables disk quorum support.
gtk2	Use gtk-2 instead of gtk-3
iscsi	Enable direct iSCSI support via net-libs/libiscsi instead of indirectly via the Linux block layer that sys-block/open-iscsi does.
jpeg	Enable jpeg image support for the VNC console server
ncurses	Enable the ncurses-based console
nfs	Enable NFS support
numa	Enable NUMA support
pin-upstream-blobs	Pin the versions of BIOS firmware to the version included in the upstream release. This is needed to sanely support migration/suspend/resume/snapshotting/etc... of instances. When the blobs are different, random corruption/bugs/crashes/etc... may be observed.
png	Enable png image support for the VNC console server
pulseaudio	Enable pulseaudio output for sound emulation
rbd	Enable rados block device backend support, see http://ceph.newdream.net/wiki/QEMU-RBD
sdl	Enable the SDL-based console
sdl2	Use libsdl2 instead of libsdl
snappy	Enable support for snappy compression
spice	Enable Spice protocol support via app-emulation/spice
ssh	Enable SSH based block device support via net-libs/libssh2
static	Build the User and Software MMU (system) targets as well as tools as static binaries
static-user	Build the User targets as static binaries
systemtap	Enable SystemTAP/DTrace tracing
tci	Enable the TCG Interpreter which can speed up or slowdown workloads depending on the host and guest CPUs being emulated. In the future it will be a runtime option but for now its compile time.
usb	Enable USB passthrough via dev-libs/libusb
usbredir	Use sys-apps/usbredir to redirect USB devices to another machine over TCP
vde	Enable VDE-based networking
vhost-net	Enable accelerated networking using vhost-net, see http://www.linux-kvm.org/page/VhostNet
virgl	Enable experimental Virgil 3d (virtual software GPU)
virtfs	Enable VirtFS via virtio-9p-pci / fsdev. See http://wiki.qemu.org/Documentation/9psetup
vte	Enable terminal support (x11-libs/vte) in the GTK+ interface
xattr	Add support for getting and setting POSIX extended attributes, through sys-apps/attr. Requisite for the virtfs backend.
xen	Enables support for Xen backends
xfs	Support xfsctl() notification and syncing for XFS backed virtual disks.

qt-virt-manager

smartcard	Enable smartcard remoting using app-emulation/libcacard

rkt

actool	Install the actool for ACI manipulation
rkt_stage1_coreos	Download and use a prebuilt stage1.aci from CoreOS
rkt_stage1_fly	Build stage1-fly.aci
rkt_stage1_host	Assemble stage1.aci from host binaries
rkt_stage1_kvm	This flag has been replaced by the rkt_stage1_kvm_* flags
rkt_stage1_kvm_lkvm	Build stage1-kvm-lkvm.aci
rkt_stage1_kvm_qemu	Build stage1-kvm-qemu.aci
rkt_stage1_src	Build the stage1.aci from source

runc

ambient	Enable support for ambient capabilities set (Requires Linux kernel 4.3 or later).
apparmor	Enable AppArmor support.

runv

libvirt	Enable support for KVM via libvirt
xen	Enable support for the Xen Hypervisor

spice

lz4	Enable support for LZ4 compression using app-arch/lz4
smartcard	Enable smartcard remoting using app-emulation/libcacard

spice-vdagent

consolekit	Use sys-auth/consolekit to determine the master vdagentd in case of multiple running vdagentds (highly recommended)

uae

scsi	Enable the uaescsi.device

vagrant

virtualbox	Use VirtualBox provider.

vice

ethernet	Enable ethernet emulation
fullscreen	Enable the ability to run fullscreen
sdlsound	Use media-libs/libsdl for sound support
vte	Enable support for x11-libs/vte in the GTK+ interface

virt-manager

policykit	Enables sys-auth/polkit authentication support, required when using app-emulation/libvirt with PolicyKit authentication
sasl	Depend on the proper libraries needed to connect to SASL-enabled libvirtd instances (e.g. Kerberos-protected instances).

virt-viewer

spice	Support connecting to SPICE-enabled virtual machines.
vnc	Support connecting to VNC-enabled virtual machines.

virt-what

dmi	Use sys-apps/dmidecode to read firmware data

virtualbox

headless	Build without any graphic frontend
lvm	Build VBoxVolInfo that needs devicemapper from sys-fs/lvm2.
pax_kernel	Apply patch needed for pax enabled kernels.
sdk	Enable building of SDK
udev	Controls installation of special USB udev rules.
vboxwebsrv	Build and install the VirtualBox webservice

virtualbox-bin

additions	Install Guest System Tools ISO
chm	Install kchmviewer binary to enable online help (in MS CHM format)
headless	Install without any graphic frontend
rdesktop-vrdp	Install the rdesktop client integration
sdk	Enable building of SDK
vboxwebsrv	Install the VirtualBox webservice

virtualbox-modules

pax_kernel	Apply patch needed for pax enabled kernels

vmware-modules

pax_kernel	Apply patch needed for pax enabled kernels
vmci	Build the Virtual Machine Communication Interface module; disable this if you want to use the module from the mainline kernel
vsock	Build the VMware VMCI transport for Virtual Sockets; disable this if you want to use the module from the mainline kernel

vmware-player

bundled-libs	Use precompiled bundled libraries instead of the system installation
ovftool	Install OVF tool for importing and exporting appliance files
vmware-tools	Install VMware Tools images

vmware-workstation

bundled-libs	Use precompiled bundled libraries instead of the system installation
ovftool	Install OVF tool.
server	Install VMware Workstation Server component.
vix	Install VIX. The VIX API allows you to write programs and scripts that automate virtual machine operations, and run programs or manipulate files within guest operating systems.
vmware-tools	Install VMware Tools images

vov

gprof	build with profiling support

wine

capi	Enable ISDN support via CAPI
custom-cflags	Bypass strip-flags; use at your own peril
d3d9	Apply highly experimental patches for Gallium Nine support. This patch may break some applications.
dos	Pull in games-emulation/dosbox to run DOS applications
gecko	Add support for the Gecko engine when using iexplore
gstreamer	Use media-libs/gstreamer to provide DirectShow functionality;
mono	Add support for .NET using Wine's Mono add-on
netapi	Use libnetapi from net-fs/samba to support Windows networks in netapi32.dll
opencl	Enable OpenCL support
osmesa	Add support for OpenGL in bitmaps using libOSMesa
pcap	Support packet capture software (e.g. wireshark)
perl	Install helpers written in perl (winedump/winemaker)
pipelight	Apply Wine-Staging patches for Pipelight/Silverlight support
prelink	Run prelink on DLLs during build; For versions before wine-1.7.55 or hardened, do not disable if you do not know what this means as it can break things at runtime
realtime	Pull in sys-auth/rtkit for low-latency pulseaudio support
run-exes	Use Wine to open and run .EXE and .MSI files
s3tc	Pull in media-libs/libtxc_dxtn for DXTn texture compression, needed for many games
samba	Add support for NTLM auth. see http://wiki.winehq.org/NtlmAuthSetupGuide and http://wiki.winehq.org/NtlmSigningAndSealing
staging	Apply Wine-Staging patches for advanced feature support that haven't made it into upstream Wine yet
themes	Support GTK+:3 window theming through Wine-Staging
udev	Use virtual/libudev to provide plug and play support

wine-any

capi	Enable ISDN support via CAPI
custom-cflags	Bypass strip-flags; use at your own peril
d3d9	Apply highly experimental patches for Gallium Nine support. This patch may break some applications.
dos	Pull in games-emulation/dosbox to run DOS applications
gecko	Add support for the Gecko engine when using iexplore
gstreamer	Use media-libs/gstreamer to provide DirectShow functionality;
mono	Add support for .NET using Wine's Mono add-on
netapi	Use libnetapi from net-fs/samba to support Windows networks in netapi32.dll
opencl	Enable OpenCL support
osmesa	Add support for OpenGL in bitmaps using libOSMesa
pcap	Support packet capture software (e.g. wireshark)
perl	Install helpers written in perl (winedump/winemaker)
pipelight	Apply Wine-Staging patches for Pipelight/Silverlight support
prelink	Run prelink on DLLs during build; For versions before wine-1.7.55 or hardened, do not disable if you do not know what this means as it can break things at runtime
realtime	Pull in sys-auth/rtkit for low-latency pulseaudio support
run-exes	Use Wine to open and run .EXE and .MSI files
s3tc	Pull in media-libs/libtxc_dxtn for DXTn texture compression, needed for many games
samba	Add support for NTLM auth. see http://wiki.winehq.org/NtlmAuthSetupGuide and http://wiki.winehq.org/NtlmSigningAndSealing
staging	Apply Wine-Staging patches for advanced feature support that haven't made it into upstream Wine yet
themes	Support GTK+:3 window theming through Wine-Staging
udev	Use virtual/libudev to provide plug and play support

wine-d3d9

capi	Enable ISDN support via CAPI
custom-cflags	Bypass strip-flags; use at your own peril
d3d9	Apply highly experimental patches for Gallium Nine support. This patch may break some applications.
dos	Pull in games-emulation/dosbox to run DOS applications
gecko	Add support for the Gecko engine when using iexplore
gstreamer	Use media-libs/gstreamer to provide DirectShow functionality;
mono	Add support for .NET using Wine's Mono add-on
netapi	Use libnetapi from net-fs/samba to support Windows networks in netapi32.dll
opencl	Enable OpenCL support
osmesa	Add support for OpenGL in bitmaps using libOSMesa
pcap	Support packet capture software (e.g. wireshark)
perl	Install helpers written in perl (winedump/winemaker)
prelink	Run prelink on DLLs during build; For versions before wine-1.7.55 or hardened, do not disable if you do not know what this means as it can break things at runtime
realtime	Pull in sys-auth/rtkit for low-latency pulseaudio support
run-exes	Use Wine to open and run .EXE and .MSI files
samba	Add support for NTLM auth. see http://wiki.winehq.org/NtlmAuthSetupGuide and http://wiki.winehq.org/NtlmSigningAndSealing
udev	Use virtual/libudev to provide plug and play support

wine-staging

capi	Enable ISDN support via CAPI
custom-cflags	Bypass strip-flags; use at your own peril
dos	Pull in games-emulation/dosbox to run DOS applications
gecko	Add support for the Gecko engine when using iexplore
gstreamer	Use media-libs/gstreamer to provide DirectShow functionality;
mono	Add support for .NET using Wine's Mono add-on
netapi	Use libnetapi from net-fs/samba to support Windows networks in netapi32.dll
opencl	Enable OpenCL support
osmesa	Add support for OpenGL in bitmaps using libOSMesa
pcap	Support packet capture software (e.g. wireshark)
perl	Install helpers written in perl (winedump/winemaker)
pipelight	Apply Wine-Staging patches for Pipelight/Silverlight support
prelink	Run prelink on DLLs during build; For versions before wine-1.7.55 or hardened, do not disable if you do not know what this means as it can break things at runtime
realtime	Pull in sys-auth/rtkit for low-latency pulseaudio support
run-exes	Use Wine to open and run .EXE and .MSI files
s3tc	Pull in media-libs/libtxc_dxtn for DXTn texture compression, needed for many games
samba	Add support for NTLM auth. see http://wiki.winehq.org/NtlmAuthSetupGuide and http://wiki.winehq.org/NtlmSigningAndSealing
staging	Apply Wine-Staging patches for advanced feature support that haven't made it into upstream Wine yet
themes	Support GTK+:3 window theming through Wine-Staging
udev	Use virtual/libudev to provide plug and play support

wine-vanilla

capi	Enable ISDN support via CAPI
custom-cflags	Bypass strip-flags; use at your own peril
dos	Pull in games-emulation/dosbox to run DOS applications
gecko	Add support for the Gecko engine when using iexplore
gstreamer	Use media-libs/gstreamer to provide DirectShow functionality;
mono	Add support for .NET using Wine's Mono add-on
netapi	Use libnetapi from net-fs/samba to support Windows networks in netapi32.dll
opencl	Enable OpenCL support
osmesa	Add support for OpenGL in bitmaps using libOSMesa
pcap	Support packet capture software (e.g. wireshark)
perl	Install helpers written in perl (winedump/winemaker)
prelink	Run prelink on DLLs during build; For versions before wine-1.7.55 or hardened, do not disable if you do not know what this means as it can break things at runtime
realtime	Pull in sys-auth/rtkit for low-latency pulseaudio support
run-exes	Use Wine to open and run .EXE and .MSI files
samba	Add support for NTLM auth. see http://wiki.winehq.org/NtlmAuthSetupGuide and http://wiki.winehq.org/NtlmSigningAndSealing
udev	Use virtual/libudev to provide plug and play support

winetricks

rar	Pull in app-arch/unrar for extraction of rar-compressed game files

x48

readline	Enables support for libreadline

xe-guest-utilities

xenstore	Use xenstore binaries bundled by Citrix instead of building app-emulation/xen-tools

xen

efi	Adds efi boot support, requires LDFLAG -melf_x86_64 for amd64
flask	Enable the Flask XSM module from NSA

xen-tools

api	Build the C libxenapi bindings
flask	Enable the Flask XSM module from NSA
hvm	Enable support for hardware based virtualization (VT-x,AMD-v)
ocaml	Enable support for the ocaml language
ovmf	Enable support to boot UEFI guest vm, needed by hvm
pam	Enable pam support
pygrub	Install the pygrub boot loader
qemu	Enable IOEMU support via the use of qemu-dm
qemu-traditional	Build the old qemu traditional device model (useful only if you cannot change to the new device model e.g. Windows VMs)
screen	Enable support for running domain U console in an app-misc/screen session
system-qemu	Using app-emulation/qemu instead of the bundled one
system-seabios	Using sys-firmware/seabios instead of the bundled one

xtrs

ls-dos	Install LS-DOS disk images for Model 4P

app-eselect

eselect-php

fpm	Enable the FastCGI Process Manager SAPI

app-forensics

afflib

fuse	Enable extra fuse thingies
qemu	Enable qemu stuff
s3	Enable support for Amazon S3

aide

e2fs	Enable support for checking file attributes on ext2/ext3/ext4 filesystems
prelink	Bypass prelinking when calculating checksums

chkrootkit

cron	Install cron script for weekly rootkit scans

libewf

bfio	Enables libbfio for chaining file in file handling
ewf	Enables the v1 API
fuse	Enable fuse support for ewfmount
rawio	Enables raw IO handling
uuid	Enable UUID support in the ewftools

openscap

gconf	Build the gconf independant probes
nss	Prefer NSS over libgcrypt as the crypto engine
rpm	Compiles the RPM probes
sce	Enables Script Check Engine (SCE) support
sql	Build the sql independant probes

ovaldi

rpm	Enable the RPM probes

quickfuzz

archs	support archive formats
codes	support cource code formats
docs	support document formats
imgs	support image formats
media	support media formats
net	support networking formats
pki	support PKI formats

sleuthkit

aff	Enable extra aff formats
ewf	Enable libewf support

app-i18n

anthy

canna-2ch	Enable support for app-dicts/canna-2ch

fcitx

autostart	Enable XDG-compatible autostart of Fcitx
enchant	Enable Enchant backend (using app-text/enchant) for spelling hinting
gtk2	Install input method module for GTK+ 2
gtk3	Install input method module for GTK+ 3
opencc	Enable OpenCC engine (using app-i18n/opencc) for converter between Simplified Chinese and Traditional Chinese
pango	Enable support for x11-libs/pango
qt4	Install input method module for Qt 4
table	Install table input methods for Simplified Chinese

fcitx-configtool

gtk3	Use GTK+3 instead of 2

fcitx-libpinyin

dictmanager	Enable dictionary manager. Requires dev-qt/qtwebkit.

fcitx-unikey

macro-editor	Install macro editor

ibus

deprecated	install the deprecated ibus python library
gconf	Enable support for gnome-base/gconf
gtk3	Enable support for gtk+3

ibus-anthy

deprecated	Install deprecated pygtk2 library

ibus-handwrite

zinnia	Build with app-i18n/zinnia engine.

ibus-libpinyin

boost	Compile against dev-libs/boost libraries
opencc	Enable support for app-i18n/opencc

ibus-m17n

gtk	Build the preference interfaces, based on x11-libs/gtk+ (GTK+ 2).

ibus-pinyin

boost	Compile against dev-libs/boost libraries

ibus-unikey

gtk3	Enable support for gtk+3

im-ja

anthy	Support for Anthy input method
skk	Support for SKK input method

imsettings

gconf	Enable GConf support
gtk3	Enable support for x11-libs/gtk+:3
xfconf	Enable integration in the Xfce desktop environment with xfce-base/xfconf

kimera

anthy	Support for Anthy input method

mozc

fcitx	Enable support for app-i18n/fcitx
ibus	Enable support for app-i18n/ibus
renderer	Enable native candidate window.

pyzy

boost	Enable support for dev-libs/boost
doc	Enable support for documents
opencc	Use app-i18n/opencc for input

scim

gtk3	Enable support for x11-libs/gtk+:3

scim-anthy

gtk3	Enable support for x11-libs/gtk+:3
kasumi	Use Anthy dictionary maintenance tool (app-dicts/kasumi)

tomoe

hyperestraier	Enable support for app-text/hyperestraier

translate-shell

tts	Enable text-to-speech support

uim

anthy	Enable support for app-i18n/anthy input method
eb	Enable support for dev-libs/eb
gtk3	Enable support for x11-libs/gtk+:3
skk	Enable support for app-i18n/skk-jisyo

app-laptop

hdapsd

libconfig	Require dev-libs/libconfig to allow the daemon to read a configuration file at startup

ibam

gkrellm	Enable building of app-admin/gkrellm module

laptop-mode-tools

scsi	Adds dependency on sdparm to control non-SATA SCSI drivers

pbbuttonsd

ibam	Enable support for Intelligent Battery Monitoring
macbook	Enable support for the Macbook and Macbook Pro

thinkfan

atasmart	include libatasmart support to get disc temperature

tp_smapi

hdaps	Install a compatible HDAPS module

app-leechcraft

lc-azoth

acetamide	Build Acetamide, the IRC protocol support
adiumstyles	Build support for Adium styles
astrality	Build Astrality, support for protocols provided by Telepathy
autoidler	Build support for automatic status changing according to user idle time
autopaste	Build Autopaste for pasting long texts to pastebins
birthdaynotifier	Build Birthday Notifier for you to not forget about birthdays of your contacts.
chathistory	Build ChatHistory which stories chat history
depester	Build Depester which enables to ignore MUC participants
embedmedia	Build EmbedMedia for embedding flash videos and images directly into chat windows
herbicide	Build Herbicide, a basic antispam plugin
hili	Build HiLi which allows to customize highlight settings in MUCs
isterique	Build Isterique plugin for neutralizing excessive caps lock usage
juick	Build plugin for the Juick.com microblogging service
keeso	Build plugin for changing text into SoMEtHInG lIKe THiS
lastseen	Build plugin for client-side recording of the last online/available time
media	Enable media calls
metacontacts	Build plugin for metacontacts support
murm	Build Murm, the VKontakte messaging support via their native API (instead of XMPP)
nativeemoticons	Build support for native Azoth's emoticons packs
otroid	Build OTRoid, plugin for the Off-the-Record deniable encryption system
sarin	Build Sarin, Tox protocol support module. Please add mva overlay to use net-libs/tox
shx	Build shell command executor plugin
standardstyles	Build support for standard Azoth styles engine
vader	Bulid Vader, the MRIM (Mail.Ru Agent) protocol support plugin
velvetbird	Build support for protocols provided by libpurple
woodpecker	Build Woodpecker, the Twitter client plugin
xtazy	Build Xtazy for publishing currently playing tune

lc-blasq

deathnote	Support LiveJournal FotoBilder service
rappor	Support VKontakte service
spegnersi	Support Flickr service
vangog	Support Picasa service

lc-blogique

hestia	Allows one to keep a local blog
metida	Support for the LiveJournal blogging platform

lc-core

qwt	Support for QML plotting item through x11-libs/qwt

lc-gmailnotifier

notify	Pull in a plugin to show notifications from GMail Notiifer
quark	Pull in a plugin to show GMail Notifier's quark

lc-lmp

fradj	Build FrAdj, the equalizer effect module
graffiti	Build media tags editor plugin
guess	Enable tags encoding guessing via the libguess library
mp3tunes	Build plugin for supporting the mp3tunes.com music locker service
mpris	Enable MPRIS support
potorchu	Enable the projectM-based visualization effects module for LMP

lc-monocle

fb2	Enable support for FictionBook format
mobi	Enable support for MOBI format

lc-musiczombie

acoustid	Use media-libs/chromaprint for acoustic fingerprinting

lc-netstoremanager

dropbox	Build Dropbox storage backend
googledrive	Build Google Drive storage backend

lc-poshuku

autosearch	Provide automatic search suggestions for Poshuku.
cleanweb	Build CleanWeb for ad blocking compatible with Firefox's AdBlock+.
dcac	Build color inverter module providing a night mode.
fatape	Build FatApe, GreaseMonkey userscripts support layer.
filescheme	Build FileScheme for accessing local URLs.
foc	Build FOC for Flash-on-Click functionality.
fua	Build FUA for faking user agents for different hosts.
keywords	Build Keywords for adjusting search shortcuts.
onlinebookmarks	Build OnlineBookmarks for syncing bookmarks with social bookmarking services like Read It Later.
qrd	Build module for displaying the QR code of a web page.
speeddial	Build SpeedDial module.
webengine	Build WebEngine- (that is, Chromium-)based rendering backend.

lc-secman

exposecontents	Build the GUI for viewing the stored data.

leechcraft-meta

de	Install components, that allow using Leechcraft as Desktop Environment

app-misc

anki

recording	Enable support for audio recording
sound	Enable support for adding sound to cards

bijiben

zeitgeist	Build the plugin to inject events to gnome-extra/zeitgeist

binwalk

graph	Enable support for generating entropy graphs

blink1

mini-tool	Build and install command-line mini-tool blink1-mini-tool (normally used for embedded devices)
server	Build and install REST API server (currently hard-coded to TCP port 8080)
tool	Build and install command-line tool blink1-tool

byobu

screen	Use app-misc/screen as the default backend

ca-certificates

cacert	Include root certs from CAcert (http://www.cacert.org/) and Software in the Public Interest (http://www.spi-inc.org/)
insecure_certs	Install certs which are known to *not* being trustworthy.

ddccontrol

pci	enable direct PCI memory access (the setuid ddcpci util)

ddcutil

enable-api-libs	Enables the C/C++ API.
usb-monitor	Adds support for monitors attached via USB.
user-permissions	Adds a udev rules to allow non-root users in the i2c group to access the /dev/i2c-* devices. If usb-monitor is selected, users will need to be added to the video group to access the USB monitor. Otherwise, only root will be able to use ddcutil.

digitemp

ds2490	Build support for the ds2490 sensor
ds9097	Build support for the ds9097 sensor
ds9097u	Build support for the ds9097u sensor

emelfm2

ansi	Add support for ANSI escape sequences
gtk3	Use x11-libs/gtk+:3 instead of x11-libs/gtk+:2

freemind

groovy	Build plugin for scripting via Groovy
latex	Build plugin for inserting mathematical formulas in LaTeX syntax
pdf	Build plugin for exporting mindmaps to SVG and PDF
svg	Build plugin for exporting mindmaps to SVG and PDF

gcstar

stats	Enable statistics reporting
tellico	Enable support for kde-misc/tellico files

geneweb

ocamlopt	Enable ocamlopt support (dev-lang/ocaml native code compiler)

geoclue

geonames	Install geonames.org provider
gsmloc	Install GSM location provider
gtk	Install gtk-based geoclue-test-gui
hostip	Install hostip.info provder
manual	Install manual provider
modemmanager	Enable geolocation through 3G or GPS enabled hardware through net-misc/modemmanager.
nominatim	Install openstreetmap.org provider
plazes	Install plazes.com provider
skyhook	Install skyhookwireless.com provider
yahoo-geo	Install Yahoo geolocation provider
zeroconf	Enable retrieval of GPS location from Android devices with https://wiki.gnome.org/Apps/GeoclueShare

gourmet

i18n	Enable support for i18n through elib.intl
ipython	Enable support for the interactive Python console plugin
pdf	Enable export to PDF
print	Enable pretty Python printing
spell	Enable support for the spell check plugin
web	Enable support for the web import plugin

gramps

geo	Enable rendering of geographical data using sci-geosciences/osm-gps-map.
reports	All external software that is needed for graphical reports will be installed

graphlcd-base

g15	Add support for app-misc/g15daemon driver (e.g. Logitech G15 Keybord)

irtrans-irserver

mono	Enable mono support

jq

oniguruma	Use dev-libs/oniguruma for regular expression support

lcd4linux

mpd	Add support for display of mpd controlled music (media-libs/libmpd)

lcdproc

ftdi	Enable support for FTDI connections in some selected LCD_DEVICES (currently hd44780)
hid	Enable HID support using libhid
irman	Enable support for IRMan (media-libs/libirman)
lcd_devices_sdeclcd	Enable support for VLSYS M428 display
lcd_devices_vlsys_m428	Enable support for VLSYS M428 display
nfs	Adds support for NFS file system
seamless-hbars	Try to avoid gaps in horizontal bars

linux-logo

nls	Add Native Language Support (using gettext - GNU locale utilities)

lirc

audio	Support using an audio device connected to an IR receiver
devinput	Support the devinput input device
ftdi	Support FTDI devices
gtk	Include GTK support which enables the use of lirc-setup
hardware-carrier	The transmitter device generates its clock signal in hardware
iguanair	Support iguanaIR devices
inputlirc	Add a dependency on app-misc/inputlircd
irman	Add a dependency on media-libs/libirman
transmitter	Add transmitter support to some lirc-drivers (e.g. serial)
uinput	Enable support for uinput

mc

edit	Compile and install the mcedit application
mclib	Compile and install the libmc.so shared library
sftp	Add support for sftp (uses net-libs/libssh2 for it).
slang	Use sys-libs/slang instead of sys-libs/ncurses.
xdg	Toggles mc's config dir location. Enable for $XDG_CONFIG_HOME/mc, disable for $HOME/.mc

mosquitto

bridge	Enable bridge support in the MQTT broker.
persistence	Store messages and subscriptions to a file.
srv	Include SRV lookup support.
websockets	Support the WebSocket protocol.

muttprint

doc	Builds documentation

neofetch

X	Enable support for detecting DEs, WMs, screen resolutions, and showing images from an X terminal

note

general	Add support for ascii flatfile backend
text	Add support for text backend

openastro

jpeg	Enable exporting Astrological Charts to jpeg
png	Enable exporting Astrological Charts to png

pax-utils

python	Install a more powerful/faster version of lddtree

recoll

camelcase	Enable indexing for camelCase sentences and words
inotify	Use the Linux Kernel notification subsystem for monitoring file alterations in realtime
session	Stop monitoring file alterations when X11 session terminates

rlwrap

debug	Enable debug

screen

multiuser	Enable multiuser support (by setting correct permissions)
nethack	Express error messages in nethack style
utmp	Include utmp support

screenfetch

X	Use the media-gfx/scrot package to take screenshots

sphinx

id64	use 64-bit document and word IDs
re2	use the dev-libs/re2 regular expression library
stemmer	Enable language stemming support

task

sync	Enable "task sync" support

tasque

hiveminder	Allows you to use http://www.hiveminder.com/ as your storage backend.
rememberthemilk	Allows you to use http://www.rememberthemilk.com/ as your storage backend.

tmux

utempter	Include libutempter support

towitoko

moneyplex	Makes libtowitoko work for the moneyplex home banking software

tracker

cue	Enable cue sheet parsing
firefox-bookmarks	Install bookmark data miner plugin for www-client/firefox and www-client/firefox-bin
gsf	Enable gnome-extra/libgsf based data extractor and for ODT.
iptc	Enable extraction of IPTC data from pictures
iso	Enable extraction of metadata from ISO disk images
miner-fs	Enable tracker-miner-fs (required for filesystem indexing)
nautilus	Enable tracker to integrate with gnome-base/nautilus by providing entries in its context menu
playlist	Add support for playlists
stemmer	Add word stemming via dev-libs/snowball-stemmer.
thunderbird	Install email data miner plugin for mail-client/thunderbird and mail-client/thunderbird-bin
xps	Add support for XPS file format through app-text/libgxps.

unfoo

minimal	Do not install all support archive binaries

vifm

X	Add support for X11
compatibility	Compatibility with previous versions of vifm
developer	Enable features of interest to developers
extended-keys	Support for extended keys (arrows, home etc)
gtk	Use gtk+ to determine mimetypes
magic	Use libmagic to determine mimetypes
vim	Install the vifm vim plugin and vim-compatible documentation
vim-plugin	Install the vifm vim plugin
vim-syntax	Pulls in related vim syntax scripts

worker

avfs	Enable support for sys-fs/avfs
magic	Add magic file support from sys-apps/file to automatically detect file types

workrave

mate	Add support for MATE panel
xfce	Add support for XFCE panel

zygrib

maps	Installs additional GSHHS maps for high resolution coastline data and cities

app-mobilephone

gammu

irda	Enables infrared support

gnokii

ical	Enable support for dev-libs/libical
irda	Enable infrared support
pcsc-lite	Enable smartcard support with sys-apps/pcsc-lite
sms	Enable SMS support (build smsd)

smstools

stats	Enable statistic reporting

app-office

abiword

collab	Enable collaborative editing plugin
goffice	Enable goffice plugin
grammar	Enable grammar checking via dev-libs/link-grammar
map	Enable world map support through media-libs/libchamplain
math	Enable support for x11-libs/gtkmathview
ots	Enable Text Summarizer plugin
plugins	Enable plugins build (see http://www.abisource.com/wiki/PluginMatrix for more information). If your file cannot be opened due lack of support, try enabling this.
redland	Enables support redland and raptor libs.
thesaurus	Enable thesaurus support
wordperfect	Enable wordperfect file support via app-text/libwpd

calligra

activities	Enable kactivities support
color-management	Enable color management via media-libs/opencolorio
eigen	Enable dev-cpp/eigen mathematical templates support
glew	Enable media-libs/glew opengl extension library support
glib	Enable support for C library routines from dev-libs/glib
gsf	Enable support for ODT structures extraction via gnome-extra/libgsf
import-filter	Enable support for various import filter file formats like WordPerfect, Visio and Apple Keynote
lcms	Build colorengine plugins using media-libs/lcms
okular	Enable bindings for kde-apps/okular
phonon	Build stage/eventplugins and videoshape plugin using media-libs/phonon
pim	Enable support for KDE PIM resources integration
spacenav	Enable support for the 3Dconnexion spacenav input device via dev-libs/libspnav
vc	Enable support for dev-libs/vc, could be a significant speed boost on krita
xbase	Enable support for xbase compatible database formats

glabels

barcode	Enable barcode support through external libraries.

gnucash

chipcard	Enable support for chipcard reading and processing.
hbci	Enable HBCI support, for connecting to some internet banks
quotes	Enable Online Stock Quote retrieval

gnumeric

libgda	Enable database support through gnome-extra/libgda.
perl	Enable perl plugin loader.
python	Enable python plugin loader.

kexi

marble	Enable displaying of maps using kde-apps/marble
mdb	Enable support for Microsoft Access database
webkit	Enable web form designer widget using dev-qt/qtwebkit

kmymoney

hbci	Enable HBCI support using net-libs/aqbanking
pim	Enable KDE PIM integration via kde-apps/kdepimlibs
quotes	Enable Online Stock Quote retrieval
weboob	Enable import of online banking transactions extracted by www-client/weboob

libreoffice

coinmp	Use sci-libs/coinor-mp as alternative solver
collada	Enable Collada for rendering 3D models stored in *.dae and *.kmz format
gltf	Use media-libs/libgltf for inserting 3D models in the glTF format into presentations
googledrive	Enable support for remote files on Google Drive
gtk3	Enable highly experimental gtk3 frontend
jemalloc	Use dev-libs/jemalloc for allocations
odk	Build the Office Development Kit
pdfimport	Enable PDF import via the Poppler library
quickstarter	Build the system tray quickstarter
telepathy	Enable document colaboration features using telepathy communication framework.
vlc	Use media-video/vlc for video embedding

libreoffice-l10n

offlinehelp	Install help files locally instead of using the LibreOffice Wiki

lyx

aspell	Add support for aspell spellchecking
dia	Add support for diagrams (app-office/dia)
docbook	Add support for docbook export
dot	Add support for DOT import (media-gfx/graphviz)
enchant	Add support for enchant spellchecking wrapper (both aspell and hunspell can be used by LyX).
gnumeric	Add support for importing Gnumeric/OpenOffice/MS Excel spreadsheets into LyX.
html	Add support for HTML import
hunspell	Add support for spellchecking based on hunspell and reuse system-wide OpenOffice dictionaries. This also enable thesaurus dictionaries not accessible via aspell.
monolithic-build	This should speed up compilation significantly when you have enough RAM (> 600 MB)
rcs	Add support for revision control via dev-vcs/rcs
rtf	Add support for RTF import/export packages

magicpoint

contrib	Install additional contributed scripts

scribus

boost	Enable support for Boost based enhancement
hunspell	Enable support for spell checking with app-text/hunspell
minimal	Don't install headers (only required for e.g. plug-in developers)
osg	3D redering via dev-games/openscenegraph
scripts	Install the scripts
templates	Document tamplates
tk	Install tk based scripts e.g. FontSample.py

skrooge

activities	Enable kactivities support
crypt	Enable encryption using dev-db/sqlcipher
designer	Build plugins for dev-qt/designer

texmacs

netpbm	Add support for media-libs/netpbm
pdf	Add the experimental native pdf export

texstudio

video	Use phonon for video embedding

wps-office

sharedfonts	Install WPS fonts available system wide

app-pda

barry

boost	Enable boost support
desktop	Install the GUI desktop control panel
gui	Install the GUI backup tool

gtkpod

clutter	Enable clutter support for displaying coverart

app-portage

conf-update

colordiff	Use colors when displaying diffs (app-misc/colordiff)
libressl	Enable SSL connections and crypto functions using dev-libs/libressl

eix

debug	Build with upstream's CXXFLAGS/LDFLAGS for debugging support; not recommended for normal use.
doc	Create description of the eix cache file additionally in html format
sqlite	Compile in support for portage's sqlite backend; to actually use it you need additional configuration of portage and eix

g-sorcery

bson	Support BSON file format for package DB

layman

bazaar	Support dev-vcs/bzr based overlays
cvs	Support dev-vcs/cvs based overlays
darcs	Support dev-vcs/darcs based overlays
g-sorcery	Support app-portage/g-sorcery based overlays
git	Support dev-vcs/git based overlays
gpg	Support app-crypt/gnupg signed overlays lists and manifests
mercurial	Support dev-vcs/mercurial based overlays
squashfs	Support mounting squashfs image overlays locally read-only
subversion	Support dev-vcs/subversion based overlays
sync-plugin-portage	Install the sys-apps/portage sync module

pfl

network-cron	Adds a cron job which does a weekly submit of the package database

tatt

templates	Install template scripts to be used with tatt

app-shells

autojump

ipython	Add support for dev-python/ipython

bash

bashlogger	Log ALL commands typed into bash; should ONLY be used in restricted environments such as honeypots
mem-scramble	Build with custom malloc/free overwriting allocated/freed memory
net	Enable /dev/tcp/host/port redirection
plugins	Add support for loading builtins at runtime via 'enable'

dash

vanilla	Support echo -n, and enable echo -e all the time (unsupported)

mpv-bash-completion

luajit	Use dev-lang/luajit instead of dev-lang/lua

pdsh

rsh	This allows the use of rsh (remote shell) and rcp (remote copy) for authoring websites. sftp is a much more secure protocol and is preferred.

scsh-install-lib

scsh	Use a non-FHS directory layout

shish

diet	Use dev-libs/dietlibc

app-text

acroread

html	HTML support and help reading capability (only for x86).

asciidoc

highlight	Enable source code highlighting

atril

caja	Enable property page extension in mate-base/caja
dvi	Enable build-in DVI viewer
epub	Enable build-in DVI viewer using net-libs/webkit-gtk
gtk3	Build with GTK+3 instead of GTK+2
t1lib	Enable the Type-1 fonts for the build-in DVI viewer (media-libs/t1lib)
xps	Enable XPS viewer using app-text/libgxps

blogc

git	Build blogc-git-receiver tool
httpd	Build blogc-runserver tool
make	Build blogc-make tool

cb2bib

webengine	Use dev-qt/qtwebengine instead of dev-qt/qtwebkit

crm114

mew	Add support for using the mewdecode mime decoder (app-emacs/mew)
mimencode	Add support for using the mimencode mime (net-mail/metamail)
normalizemime	Add support for using the normalizemime (mail-filter/normalizemime)

dbacl

interactive	Enable the interactive mailinspect ability

dictd

judy	Build Judy-based (dev-libs/judy) plugin implementing fast "exact" and especially "lev" strategies
minimal	Don't build server but dict client, dictzip and dictfmt only.

docbook-sgml-utils

jadetex	Add support for app-text/jadetex (for processing tex files produced by the TeX backend of Jade)

docbook-xsl-ns-stylesheets

ruby	Install the Ruby-based dbtoepub script; requires an interpreter compatible with app-eselect/eselect-ruby.

docbook-xsl-stylesheets

ruby	Install the Ruby-based dbtoepub script; requires an interpreter compatible with app-eselect/eselect-ruby.

ebook-tools

lit2epub	Install lit2epub script

editorconfig-core-c

cli	Install command line interface.

enchant

aspell	Adds support for app-text/aspell spell checker
hunspell	Adds support for app-text/hunspell spell checker
zemberek	Adds support for app-text/zemberek-server spell checker server

evince

dvi	Enable the built-in DVI viewer
nautilus	Enable property page extension in gnome-base/nautilus
t1lib	Enable the Type-1 fonts for the built-in DVI viewer (media-libs/t1lib)
xps	Enable XPS viewer using app-text/libgxps

getxbook

ocr	Use app-text/tesseract for optical character recognition

ghostscript-gpl

unicode	Add support for unicode passwords via net-dns/libidn

glark

zip	Support for ZIP files using dev-ruby/rubyzip

groonga

abort	Enable query abortion
benchmark	Build benchmark programs
dynamic-malloc-change	Allow dynamic memory allocation change for testing
exact-alloc-count	Atomic counting for memory alloc count
fmalloc	Make memory allocation failed in specified condition for debug
futex	Use futex
libevent	Enable dev-libs/libevent used for suggestion
mecab	Use app-text/mecab for morphological analysis
msgpack	Enable dev-libs/msgpack used for suggestion
nfkc	Use nfkc based utf8 normalization
sphinx	Enable document generation by app-misc/sphinx
uyield	Build for detecting race conditions
zeromq	Enable net-libs/zeromq used for suggestion

gtranslator

gnome-dictionary	Enable plugin for dictionary lookups using app-dicts/gnome-dictionary.
gucharmap	Enable plugin for unicode symbols selection using gnome-extra/gucharmap.

hyperestraier

mecab	Enable app-text/mecab support for Estraier

jmupdf

system-mupdf	Link against system version of app-text/mupdf

lcdf-typetools

kpathsea	Enable integration with kpathsea search library (TeX related)

libebook

tools	Build file conversion tools

libmwaw

tools	Build file conversion tools

libstaroffice

tools	Build conversion tools
zlib	Enable support for compressed data

libwpd

tools	Build file conversion tools

libwps

tools	Build file conversion tools

mathtex

png	Generate png images by default instead of gif

mupdf

openssl	Use dev-libs/openssl crypto backend

pandoc

embed_data_files	Embed data files in binary for relocatable executable.
http-conduit	Enable downloading of resources over https.
https	Enable support for downloading of resources over https.
make-pandoc-man-pages	Build program to regenerate pandoc man pages from README.
network-uri	Get Network.URI from the network-uri package.
trypandoc	Build trypandoc cgi executable.
weigh-pandoc	Build weigh-pandoc to measure memory usage.

pastebinit

crypt	Install pbputs for gpg-encrypted pastes

pdfgrep

unac	Removing accents and ligatures before search

pelican

markdown	Markdown support

podofo

boost	Add support for boost
tools	Build and install commandline tools.

poppler

cairo-qt	Enable experimental Cairo font rasterizer for Qt4 backend.
nss	Enable signatures handling with dev-libs/nss
utils	Install command-line PDF converters and various utilities.

qpdf

perl	Install fix-qdf tool (for reverting PDF edits) written in perl

qpdfview

fitz	Use experimental fitz rendering, provided by app-text/mupdf, instead of poppler
synctex	Add support for searching TeX sources

sdcv

darkterm	Improve readability of color output on terminals with dark background.

sgmltools-lite

jadetex	Add support for app-text/jadetex (for processing tex files produced by the TeX backend of Jade)

stardict

advertisement	Enable stardict advertisements plugin
cal	Enable calendar support using cal program
dictdotcn	Enable dict.cn network plugin (for Chinese language)
espeak	Enable text to speech synthesizer plugin using app-accessibility/espeak engine
flite	Enable text to speech synthesizer plugin using app-accessibility/flite engine
fortune	Enable plugin to read fortune messages using games-misc/fortune-mod. You may consider installing games-misc/fortune-mod-all to get all fortune messages.
gucharmap	Enable plugin for unicode symbols description using gnome-extra/gucharmap
htmlparse	Enable plugin to parse dictionaries with html content
info	Enable plugin to read info pages
man	Enable plugin to read manual pages
powerwordparse	Enable plugin to parse powerword dictionaries
pronounce	Install WyabdcRealPeopleTTS package (it is just many .wav files) to make StarDict pronounce English words
qqwry	Enable QQWry plugin, which provides information (in Chinese language) about geographical positions, owner, etc. for IP addresses
tools	Build and install dictionary management tools and converters from various dictionary formats
updateinfo	Enable plugin to check for stardict updates
wikiparse	Enable plugin to parse dictionaries in wikimedia format
wordnet	Enable wordnet plugin to find similar English words using lexical database
xdxfparse	Enable plugin to parse dictionaries in xdxf (XML Dictionary eXchange Format)
youdaodict	Enable youdao.com network plugin (for Chinese language)

tesseract

math	Enable support for recognition of equations.
opencl	Enable opencl support for speedup using GPU computation.
osd	Enable support orientation and script detection.
scrollview	Install viewer to debug recognition (ScrollView).
training	Install training applications to add support for new languages.
webp	Enable support for webp image format.

texlive

context	Add support for the ConTeXt format (dev-texlive/texlive-context)
detex	Add support for dev-tex/detex, a filter program that removes the LaTeX (or TeX) control sequences
dvi2tty	Add support for dev-tex/dvi2tty to preview dvi-files on text-only devices
dvipdfm	Add support for app-text/dvipdfm to convert DVI files to PDF
epspdf	Add support for app-text/epspdf, a tool for converting [e]ps files to pdf.
extra	Add support for extra TeXLive packages
games	Add typesetting support for games (chess, etc.) (dev-texlive/texlive-games)
graphics	Add support for several graphics packages (pgf, tikz,...)
humanities	Add LaTeX support for the humanities (dev-texlive/texlive-humanities)
jadetex	Add support for app-text/jadetex (for processing tex files produced by the TeX backend of Jade)
luatex	Add extra support for luatex
metapost	Add support for metapost: A tool for creating graphics in scalable PostScript.
music	Add support for music typesetting (dev-texlive/texlive-music)
omega	Add omega packages (dev-texlive/texlive-omega)
pdfannotextractor	Add dev-tex/pdfannotextractor support, for extracting annotations from PDF files.
pstricks	Add pstricks packages (dev-texlive/texlive-pstricks)
publishers	Add support for publishers (dev-texlive/texlive-publishers)
science	Add typesetting support for natural and computer sciences (dev-texlive/texlive-science)
tex4ht	Add support for dev-tex/tex4ht (for converting (La)TeX to (X)HTML, XML and OO.org)
texi2html	Add support for app-text/texi2html which converts texi files to HTML.
xetex	Add support for XeTeX macros (dev-texlive/texlive-xetex)
xindy	Add support for app-text/xindy, a flexible indexing system

texlive-core

luajittex	Add support for LuaJitTeX: LuaTeX based on LuaJIT which is usually faster.
xetex	Add support for XeTeX: a TeX system with Unicode and modern font technologies.

wdiff

experimental	Build experimental utilities (mdiff, unify, wdiff2)

webgen

builder	Enable programmatic HTML/XML generation
highlight	Enable syntax highlighting for certain plugins
markdown	Markdown support

wklej

vim	Install the vim plugin allowing to paste through ':Wklej'.

writerperfect

abiword	Add support for abiword format using app-text/libabw
ebook	Add support for various ebook formats using app-text/libebook
freehand	Add support for freehand format using media-libs/libfreehand
gsf	Add support for structured files using gnome-extra/libgsf
keynote	Add support for keynote format using app-text/libetonyek
mspub	Add support to mspub format using app-text/libmspub
mwaw	Add support to mwaw formats using app-text/libmwaw
pagemaker	Add support to pagemaker formats using media-libs/libpagemaker
visio	Add support for visio format using media-libs/libvisio
wpd	Add support for wpd format using app-text/libwpd
wpg	Add support for wpg format using app-text/libwpg
wps	Add support for wps format using app-text/libwps

wv

tools	Install optional utilities considered deprecated in favor of using AbiWord.

xmlto

text	Support conversion from XML to plain text

yagf

cuneiform	Enable support for the app-text/cuneiform OCR engine.
tesseract	Enable support for the app-text/tesseract OCR engine.

zathura

magic	Use libmagic to determine mimetypes
synctex	Use libsynctex to get latex codeline from pdf

zathura-meta

cb	Install plug-in for ComicBook support

app-vim

gentoo-syntax

ignore-glep31	Remove GLEP 31 (UTF-8 file encodings) settings

vim-latex

html	Install HTML documentation
python	Enable python support which can help speed up some functionality

youcompleteme

clang	Enable semantic support for C-family languages using sys-devel/clang

dev-ada

gnat_util

shared	Build gnat_util shared library
static	Build gnat_util static library
static-pic	Build gnat_util static library with pic code

gnatcoll

postgresql	Adds support for postgresql
projects	Adds support for projects
pygobject	Adds support for pygobject
shared	Build shared library
static	Build static library

gprbuild

shared	Build shared library
static	Build static library
static-pic	Build static library with pic code

gtkada

shared	Build gtkada as shared library
static	Build gtkada as static library

xmlada

shared	Build shared library
static	Build static library
static-pic	Build static library with pic code

dev-cpp

eigen

c++11	Build using the C++11 standard
cpu_flags_x86_f16c	Take advantage of CPU feature f16c
cuda	Build with cuda support

glog

gflags	Use dev-cpp/gflags for flag parsing
unwind	Use sys-libs/libunwind for stack unwinding instead of glibc/gcc (may be more reliable on x86_64)

libcmis

man	Build and install man pages.

libjson-rpc-cpp

http-client	Build support for HTTP client using net-misc/curl
http-server	Build support for HTTP server using net-libs/libmicrohttpd
stubgen	Build header stub code generator (needed for development and when pregenerated headers are not bundled)

pficommon

fcgi	Build FCGI feature
mprpc	Build MessagePack RPC feature

websocketpp

boost	Use dev-libs/boost instead of C++11

xsd

ace	Enable support for serializing to/from an ACE CDR stream

dev-db

aerospike-server-community

tools	Install extra tools

cppdb

mysql_internal	Don't build a separate mysql loadable module but rather build it into the cppdb library itself
odbc_internal	Don't build a separate postgresql loadable module but rather build it into the cppdb library itself
postgres_internal	Don't build a separate odbc loadable module but rather build it into the cppdb library itself
sqlite_internal	Don't build a separate sqlite3 loadable module but rather build it into the cppdb library itself

firebird

server	Install the server components of Firebird, not just the client
superserver	Install SuperServer
xinetd	Install ClassicServer

haildb

debug	Enable extra debug codepaths and assertions. If disabled, both the debug code and assertions are removed from the resulting binaries. Optimisations are untouched.
zlib	Add support for compressed tables through sys-libs/zlib.

maatkit

udf	Build the MySQL UDFs shipped with maatkit, requires non-minimal MySQL

mariadb

backup	Build mariadb-backup which supports SST and hot backup of InnoDB, Aria and MyISAM including compression and encryption
cluster	Add support for NDB clustering (deprecated)
community	Enables the community features from upstream.
embedded	Build embedded server (libmysqld)
extraengine	Add support for alternative storage engines (Archive, CSV, Blackhole, Federated(X), Partition)
galera	Enables galera replication
innodb-lz4	Enables lz4 compression methods for InnoDB/XtraDB
innodb-lzo	Enables lzo compression methods for InnoDB/XtraDB
innodb-snappy	Enables snappy compression methods for InnoDB/XtraDB using app-arch/snappy
jdbc	Enable the CONNECT engine to access foreign databases via JDBC
jemalloc	Use dev-libs/jemalloc for allocations.
latin1	Use LATIN1 encoding instead of UTF8
libressl	Enable SSL connections and crypto functions using dev-libs/libressl
max-idx-128	Raise the max index per table limit from 64 to 128
minimal	Install client programs only, no server
mroonga	Add support for the Mroonga engine for interfacing with the Groonga text search
openssl	Enable SSL connections and crypto functions using dev-libs/openssl
oqgraph	Add support for the Open Query GRAPH engine
pam	Enable the optional PAM authentication plugin for the server
profiling	Add support for statement profiling (requires USE=community).
server	Build the server program
sphinx	Add suport for the sphinx full-text search engine
sst-rsync	Add tools needed to support the rsync SST method
sst-xtrabackup	Add tools needed to support the xtrabackup and xtrabackup-v2 SST methods
systemtap	Build support for profiling and tracing using dev-util/systemtap
test	Install upstream testsuites for end use.
tokudb	Add support for TokuDB storage engine
yassl	Enable SSL connections and crypto functions using the bundled yaSSL

mariadb-galera

embedded	Build embedded server (libmysqld)
extraengine	Add support for alternative storage engines (Archive, CSV, Blackhole, Federated(X), Partition)
jdbc	Enable the CONNECT engine to access foreign databases via JDBC
jemalloc	Use dev-libs/jemalloc for allocations.
latin1	Use LATIN1 encoding instead of UTF8
libressl	Enable SSL connections and crypto functions using dev-libs/libressl
openssl	Enable SSL connections and crypto functions using dev-libs/openssl
oqgraph	Add support for the Open Query GRAPH engine
profiling	Add support for statement profiling (requires USE=community).
server	Build the server program
sphinx	Add suport for the sphinx full-text search engine
sst-rsync	Add tools needed to support the rsync SST method
sst-xtrabackup	Add tools needed to support the xtrabackup and xtrabackup-v2 SST methods
systemtap	Build support for profiling and tracing using dev-util/systemtap
test	Install upstream testsuites for end use.
tokudb	Add support for TokuDB storage engine
yassl	Enable SSL connections and crypto functions using the bundled yaSSL

maxscale

jemalloc	Use dev-libs/jemalloc for allocations
rabbitmq	Add support for RabbitMQ message queue

mongodb

mms-agent	Install the MongoDB Monitoring Service agent
tools	Install the MongoDB tools (mongoimport, mongodump...) from app-admin/mongo-tools

mysql

cluster	Add support for NDB clustering (deprecated)
community	Enables the community features from upstream.
embedded	Build embedded server (libmysqld)
extraengine	Add support for alternative storage engines (Archive, CSV, Blackhole, Federated(X), Partition)
jemalloc	Use dev-libs/jemalloc for allocations.
latin1	Use LATIN1 encoding instead of UTF8
libressl	Enable SSL connections and crypto functions using dev-libs/libressl
max-idx-128	Raise the max index per table limit from 64 to 128
minimal	Install client programs only, no server
openssl	Enable SSL connections and crypto functions using dev-libs/openssl
profiling	Add support for statement profiling (requires USE=community).
server	Build the server program
systemtap	Build support for profiling and tracing using dev-util/systemtap
test	Install upstream testsuites for end use.
yassl	Enable SSL connections and crypto functions using the bundled yaSSL

mysql-cluster

cluster	Add support for NDB clustering
community	Enables the community features from upstream.
embedded	Build embedded server (libmysqld)
extraengine	Add support for alternative storage engines (Archive, CSV, Blackhole, Federated(X), Partition)
jemalloc	Use dev-libs/jemalloc for allocations.
latin1	Use LATIN1 encoding instead of UTF8
libressl	Enable SSL connections and crypto functions using dev-libs/libressl
max-idx-128	Raise the max index per table limit from 64 to 128
minimal	Install client programs only, no server
openssl	Enable SSL connections and crypto functions using dev-libs/openssl
profiling	Add support for statement profiling (requires USE=community).
systemtap	Build support for profiling and tracing using dev-util/systemtap
test	Install upstream testsuites for end use.
yassl	Enable SSL connections and crypto functions using the bundled yaSSL

mysql-connector-c++

gcov	Build coverage support

oracle-instantclient

jdbc	Support for XA, Internationalization, and RowSet operations under JDBC.
odbc	Libraries for enabling ODBC applications.
sdk	Header files and an example makefile for developing Oracle applications.
sqlplus	Libraries and executable for running SQL*Plus.
tools	Workload Replay Client.

percona-server

embedded	Build embedded server (libmysqld)
extraengine	Add support for alternative storage engines (Archive, CSV, Blackhole, Federated(X), Partition)
jemalloc	Use dev-libs/jemalloc for allocations.
latin1	Use LATIN1 encoding instead of UTF8
libressl	Enable SSL connections and crypto functions using dev-libs/libressl
numa	Enable NUMA support using sys-process/numactl (NUMA kernel support is also required)
openssl	Enable SSL connections and crypto functions using dev-libs/openssl
profiling	Add support for statement profiling (requires USE=community).
server	Build the server program
systemtap	Build support for profiling and tracing using dev-util/systemtap
test	Install upstream testsuites for end use.
tokudb	Add support for TokuDB storage engine
tokudb-backup-plugin	Builds the TokuDB backup plugin
yassl	Enable SSL connections and crypto functions using the bundled yaSSL

pgadmin3

databasedesigner	Enable the Database Designer component

pgbouncer

libevent	Use libevent 2.0+ and evdns as the DNS backend
udns	Use udns as the DNS backend. Supports IPv4 only.

pgpool2

memcached	Use memcached for query caching.

pgrouting

drivingdistance	Enable to calculate driving distance
html	Install HTML formatted documentation

phpmyadmin

setup	Installs the phpMyAdmin setup utility. Users who don't use the utility should disable this USE flag for security reasons as the setup tool was the target of various exploits in the past.

postgis

gtk	Build shp2pgsql-gui a graphical interface to shp2pgsql

postgresql

pg_legacytimestamp	Use double precision floating-point numbers instead of 64-bit integers for timestamp storage.
server	Disable to build and install the clients and libraries only.
uuid	Enable server side UUID generation (via dev-libs/ossp-uuid).

psqlodbc

iodbc	Use dev-db/libiodbc. Disable to use dev-db/unixODBC.

recutils

curl	Enable support for remote descriptors using libcurl
mdb	Build the mdb2rec utility
uuid	Enable support for uuid types

redis

jemalloc	Use dev-libs/jemalloc for allocations.
luajit	Use dev-lang/luajit instead of dev-lang/lua
tcmalloc	Use tcmalloc from dev-util/google-perftools for allocations.

rethinkdb

jemalloc	Use dev-libs/jemalloc for allocations (default).
tcmalloc	Use tcmalloc from dev-util/google-perftools for allocations.

soci

boost	Enable boost support
empty	Build the sample backend called Empty

spatialite

geos	Add the sci-libs/geos library for exact topological tests
proj	Add the sci-libs/proj library for reprojection features
xls	Add the dev-libs/freexl library for xls import support

sqlite

secure-delete	Enable overwriting of deleted content with zeros by default (http://sqlite.org/pragma.html#pragma_secure_delete), causing some performance penalty
tools	Install additional tools

sqlitestudio

cli	Build CLI interface

tokumx

pax_kernel	Apply patch needed for hardened kernels

unixODBC

minimal	Disable bundled drivers and extra libraries (most users don't need these)
odbcmanual	Administrator, Internal Structure, Programmer and User documentation

dev-embedded

avrdude

ftdi	Enable support for USB FTDI chips via dev-embedded/libftdi

libftdi

tools	build ftdi_eeprom helper tool

openocd

blaster	Enable support for Altera USE-Blaster
cmsis-dap	Support for CMSIS-DAP compliant adapters
dummy	Build the dummy port driver
ftd2xx	Enable support for USB FTDI chips via dev-embedded/libftd2xx
ftdi	Enable support for USB FTDI chips via dev-embedded/libftdi
jlink	Build the SEGGER J-Link driver
minidriver	Build the dummy minidriver
parport	Enable support for parport JTAG devices
presto	Enable support for AXIS PRESTO devices
segger	Enable support for the Segger J-Link JTAG
stlink	Enable building support for the ST-Link JTAG Programmer
verbose-io	Verbose IO and comm JTAG and USB messages
versaloon	Enable building support for the Versallon-lInk JTAG

sdcc

boehm-gc	Enable Hans Boehm's garbage collector dev-libs/boehm-gc
device-lib	Enable built of devices libraries
ds390	Add support for Dallas DS390
ds400	Add support for Dallas DS400
gbz80	Add support for Gameboy gbz80
hc08	Add support for Freescale/Motorola HC08 based
mcs51	Add support for Intel mcs51
non-free	Enable non-free runtime library parts
packihx	Enable Intel HEX files pack utility
pic14	Add support for Microchip 14 bits PICs
pic16	Add support for Microchip 16 bits PICs
r2k	Add support for Rabbit 2000
r3ka	Add support for Rabbit 3000A
s08	Add support for Freescale/Motorola S08
sdbinutils	Enable SDCC library archive utilities sdar, sdranlib, sdnm
sdcdb	Enable SDCC source level debugger
sdcpp	Enable SDCC preprocessor based on GCC cpp
stm8	Add support for STMicroelectronics STM8
tlcs90	Add support for TLCS-90
ucsim	Enable software simulator for microcontrollers
z180	Add support for Zilog Z180
z80	Add support for Zilog Z80

urjtag

ftd2xx	Enable support for USB FTDI chips via dev-embedded/libftd2xx
ftdi	Enable support for USB FTDI chips via dev-embedded/libftdi

dev-games

aseprite

bundled-libs	Use the upstream provided bundled version of allegro 4.4.2
gtk3	Enable support for the experimental native GTK File Dialog
webp	Enable webp image format support

cegui

devil	Build the DevIL based ImageCodec module
freeimage	Build the FreeImage based ImageCodec module
irrlicht	Enable the Irrlicht renderer
ogre	Enable the OGRE renderer
tinyxml	Enable the Tiny XML parser module
xerces-c	Enable the Xerces-C++ XML parser module
zip	Enable the Minizip resource provider

crystalspace

3ds	Enables support for .3DS files in CrystalSpace
bullet	include support for Bullet library
cal3d	include support for skeleton animation
cegui	include support for Crazy Eddie GUI
cg	NVIDIA toolkit plugin
ode	include support for Open Dynamics Engine

guichan

allegro	Build the Allegro frontend

mygui

linguas_ru	Install some additional russian docs if 'doc' useflag enabled
ogre	Use the ogre render subsystem. (cannot combine with opengl)
opengl	Use the opengl render subsystem. (cannot combine with ogre)
plugins	Build MyGUI plugins
samples	Install MyGUI demos (needs ogre USE flag)
tools	Build the tools for development

ode

double-precision	more precise calculations at the expense of speed
gyroscopic	enable gyroscopic term (may cause instability)

ogre

boost	enable boost support
cg	NVIDIA toolkit plugin
double-precision	more precise calculations at the expense of speed
freeimage	support images via freeimage
gl3plus	Build OpenGL 3+ RenderSystem (EXPERIMENTAL)
gles2	build OpenGL ES 2.x RenderSystem
gles3	Enable OpenGL ES 3.x Features
ois	pull in Object-oriented Input System library for samples
poco	when USE=threads, use poco for threading
tbb	when USE=threads, use tbb for threading
tools	build+install helper tools
zip	support zip archives

openscenegraph

asio	Enable support for dev-cpp/asio library
fox	Build examples using x11-libs/fox library
gdal	Enable support for sci-libs/gdal library
las	Enable support for geospatial data LAS LiDAR format using sci-geosciences/liblas
openinventor	Build OpenInventor plugin
osgapps	Build osg applications
sdl2	Use media-libs/libsdl2 additionally to media-libs/libsdl
xrandr	Enable support for the X xrandr extension

physfs

grp	Enable Build Engine GRP archive support
hog	Enable Descent I/II HOG archive support
mvl	Enable Descent I/II MVL archive support
qpak	Enable Quake I/II QPAK archive support
wad	Enable Doom WAD archive support
zip	Enable ZIP archive support

simgear

dns	Enable DNS resolver via net-libs/udns
gdal	Enable alternative terrain engine based on pagedLOD via sci-libs/gdal
subversion	Enable terrasync scenery downloader

dev-haskell

abstract-deque

usecas	Enable the reference implementation to use hardware compare-and-swap.

aeson-pretty

lib-only	don't build 'aeson-pretty' executable.

ansi-terminal

example	Build the example application.

ansi-wl-pprint

example	Build the example application.

authenticate

network-uri	Get Network.URI from the network-uri package

bifunctors

semigroups	You can disable the use of the `semigroups` package using `-f-semigroups`. Disabing this is an unsupported configuration, but it may be useful for accelerating builds in sandboxes for expert users.
tagged	You can disable the use of the `tagged` package using `-f-tagged`. Disabing this is an unsupported configuration, but it may be useful for accelerating builds in sandboxes for expert users.

biosff

fclip	Build the fclip executable.
flower	Build the flower executable.
frecover	Build the frecover executable.

blaze-builder-enumerator

newbuilder	use bytestring-builder instead of blaze-builder-0.3

bytedump

executable	build executable file

bytes

test-doctests	Enable the doctest suite when using the enable-tests option for cabal.

c2hs

regression	run regression tests

cabal-install

network-uri	Get Network.URI from the network-uri package.
noprefs	Ignore 'preferred-versions' file from hackage's tarball.

certificate

executable	Build the executable

cgi

extensible-exceptions-in-base	Required to be enabled for >=dev-lang/ghc-7.
network-uri	Get Network.URI from the network-uri package.

chell

color-output	use colors in program output

citeproc-hs

bibutils	use Chris Putnam's app-text/bibutils
embed_data_files	Embed locale files into the library (needed for windows packaging)
hexpat	use dev-haskell/hexpat instead of dev-haskell/xml for XML parsing
network	use dev-haskell/network and dev-haskell/http to retrieve CSL file from URIs
small_base	Choose the new smaller, split-up base package.
unicode_collation	Use Haskell bindings to the dev-libs/icu

cmdargs

quotation	Build quote module
testprog	Build the test program

comonad

containers	You can disable the use of the `containers` package using `-f-containers`. Disabing this is an unsupported configuration, but it may be useful for accelerating builds in sandboxes for expert users.
contravariant	You can disable the use of the `contravariant` package using `-f-contravariant`. Disabling this is an unsupported configuration, but it may be useful for accelerating builds in sandboxes for expert users. If disabled we will not supply instances of `Contravariant`
distributive	You can disable the use of the `distributive` package using `-f-distributive`. Disabling this is an unsupported configuration, but it may be useful for accelerating builds in sandboxes for expert users. If disabled we will not supply instances of `Distributive`
test-doctests	Run the doctests test suite

conduit

nohandles	experimental code to use raw system calls in place of handles. Not recommended for general use

configfile

buildtests	Build the executable to run unit tests.

contravariant

safe	Get Safe guarantees rather than merely Trustworthy, but with worse constant factors.
semigroups	You can disable the use of the `semigroups` package using `-f-semigroups`. Disabling this is an unsupported configuration, but it may be useful for accelerating builds in sandboxes for expert users.
statevar	You can disable the use of the `StateVar` package using `-f-StateVar`. Disabling this is an unsupported configuration, but it may be useful for accelerating builds in sandboxes for expert users.
tagged	You can disable the use of the `tagged` package on older versons of GHC using `-f-tagged`. Disabling this is an unsupported configuration, but it may be useful for accelerating builds in sandboxes for expert users.

cpu

executable	build 'cpuid' tool

crypto-api

all_cpolys	Build all the CMAC polynomes up to 10000 bits instead of just the usual ones

crypto-conduit

conduit11	Use conduit >= 1.1.

cryptohash

cryptoapi	Defines crypto-api instances

cryptonite

integer-gmp	Whether or not to use GMP for some functions
support_aesni	allow compilation with AESNI on system and architecture that supports it
support_blake2_sse	Use SSE optimized version of BLAKE2
support_deepseq	add deepseq instances for cryptographic types
support_pclmuldq	Allow compilation with pclmuldq on architecture that supports it
support_rdrand	allow compilation with AESNI on system and architecture that supports it

dav

network-uri	Get Network.URI from the network-uri package.

distributive

lib-werror	Compile with the ghc -Werror option

encoding

systemencoding	Provide the getSystemEncoding action to query the locale.

entropy

halvm	Build for the HaLVM.

filestore

maxcount	Make use of a recent (>= 2.3.0) Darcs feature which vastly improves the performance of 'latest'. You should disable this flag if you plan to use gitit with an older version of Darcs, or 'latest' will raise an error.

glib

closure_signals	Use the the GClosure-based signals implementation.

gtk

deprecated	Include definitions in this library that are considered obsolete.
fmode-binary	Set the default file translation mode for file I/O operations to _O_BINARY.
gio	Depend on GIO package, thereby enabling certain features.

gtk2hs-buildtools

closuresignals	Use the the GClosure-based signals implementation.

gtk3

fmode-binary	Set the default file translation mode for file I/O operations to _O_BINARY.
gio	Depend on GIO package, thereby enabling certain features.

hackage-security

use-network-uri	Get Network.URI from the network-uri package.

happstack-server

network-uri	Get Network.URI from the network-uri package
template_haskell	Description: Template Haskell is available on this system

hashed-storage

diff	Provide the Storage.Hashed.Diff module.
hpc	Compile with the profiling ghc flag -fhpc.

hashtables

bounds-checking	if on, use bounds-checking array accesses
portable	if on, use only pure Haskell code and no GHC extensions.
unsafe-tricks	turn on unsafe GHC tricks

haskeline

legacy-encoding	Use legacy iconv encoding for POSIX. This is only intended for testing.
libiconv	Explicitly link against the libiconv library.
terminfo	Use the terminfo package for POSIX consoles.

hdbc-odbc

buildstresstest	Build stress test

hdbc-sqlite3

buildtests	Build the executable to run unit tests
splitbase	Choose the new smaller, split-up package.

highlighting-kate

executable	Build the Highlight executable.
pcre-light	Use the pcre-light library instead of regex-pcre-builtin.

hit

executable	Build the executable

hlint

gpl	Use GPL libraries, specifically hscolour.

hps

build-exec	Build the `hps-fractals' executable

hs3

network-uri	Get Network.URI from the network-uri package.

hslogger

buildtests	Build the executable to run unit tests.

hslua

apicheck	Compile Lua with -DLUA_USE_APICHECK..
system-lua	Use the system-wide lua instead of the bundled copy.

hsopenssl

fast-bignum	Enable fast moving of bignums between OpenSSL and GMP (GHC Only)

http

conduit10	Use version 1.0.x or below of the conduit package (for the test suite).
network-uri	Get Network.URI from the network-uri package.

http-api-data

use-text-show	Use text-show library for efficient ToHttpApiData implementations

http-client

network-uri	Get Network.URI from the network-uri package.

http-streams

network-uri	Get Network.URI from the network-uri package.

httpd-shed

buildexamples	Build example executables.
network-uri	Get Network.URI from the network-uri package.

hxt

network-uri	Get Network.URI from the network-uri package.

icalendar

network-uri	use network-uri package

json

generic	Add support for generic encoder (dev-haskell/syb)
mapdict	Encode Haskell maps as JSON dicts
parsec	Add support for parsing with Parsec
pretty	Add support for using pretty printing combinators

language-dot

executable	Build the `ppdot' executable

lens

benchmark-uniplate	Enable benchmarking against Neil Mitchell's uniplate library for comparative performance analysis. Defaults to being turned off to avoid the extra dependency.
dump-splices	Build and run the doctests test-suite.
inlining	Generate inline pragmas when using template-haskell. This defaults to enabled, but you can to shut it off to benchmark the relative performance impact, or as last ditch effort to address compile errors resulting from the myriad versions of template-haskell that all purport to be 2.8.
j	Attempt a parallel build with GHC 7.8.
lib-werror	Turn on ghc-options: -Werror
old-inline-pragmas	Some 7.6.1-rc1 users report their TH still uses old style inline pragmas. This lets them turn on inlining.
safe	Disallow unsafeCoerce
test-doctests	Build and run the doctests test-suite.
test-hlint	You can disable the hlint test suite with -f-test-hlint
test-hunit	You can disable the hunit test suite with -f-test-hunit
test-properties	Build the properties test if we're building tests
test-templates	Build the test templates if we're building tests
trustworthy	Assert that we are trustworthy when we can

lifted-async

monad-control-1	Use moand-control == 1.*

linear

template-haskell	You can disable the use of the `template-haskell` package using `-f-template-haskell`. Disabling this is an unsupported configuration, but it may be useful for accelerating builds in sandboxes for expert users.

monad-control

instancest	If enabled this package will export MonadBaseControl instances for the lazy and strict ST monad. If disabled these instances are only exported when base >= 4.4. If enabled it is required that the transformer-base package exports MonadBase instances for ST. It will do this by default.

monad-logger

template_haskell	Enable Template Haskell support.

monad-par

chaselev	Use Chase-Lev Deques for higher-perf work-stealing.

nats

hashable	You can disable the use of the `hashable` package using USE=-hashable. Disabling this is an unsupported configuration, but it may be useful for accelerating builds in sandboxes for expert users. If set we will not supply an instance of `Hashable`.

network-data

small_base	Build the split-up base package.

pandoc-citeproc

bibutils	use Chris Putnam's app-text/bibutils
embed_data_files	Embed locale files into the library (needed for windows packaging)
hexpat	use dev-haskell/hexpat instead of dev-haskell/xml for XML parsing
network	use dev-haskell/network and dev-haskell/http to retrieve CSL file from URIs
small_base	Choose the new smaller, split-up base package.
test_citeproc	Build the test-citeproc program
unicode_collation	Use Haskell bindings to the dev-libs/icu

persistent

nooverlap	Use OverlappingInstances only for String. Only developers should use this.

persistent-sqlite

build-sanity-exe	Build a sanity check test executable.

pointed

comonad	optional instances
containers	optional instances
kan-extensions	optional instances
semigroupoids	optional instances
semigroups	optional instances
stm	optional instances
tagged	optional instances
transformers	optional instances
unordered-containers	optional instances

publicsuffixlist

create	export Network.PublicSuffixList.Create module
runtimelist	read suffix list from dist at startup instead of embedding list into library

quickcheck

template_haskell	Enable additional test modules requiring Template Haskell support.

recaptcha

network-uri	Get Network.URI from the network-uri package.

reflection

template-haskell	Enable template haskell.

rfc5051

mkunicodedata	build codes generator itself

sandi

with-conduit	Build with conduit

scientific

bytestring-builder	Provide the Data.ByteString.Builder.Scientific module (requires bytestring >= 0.10).

semigroupoid-extras

profunctors	You can disable the use of the `profunctors` package using `-f-profunctors`. Disabing this is an unsupported configuration, but it may be useful for accelerating builds in sandboxes for expert users.

semigroupoids

comonad	You can disable the use of the `comonad` package using `-f-comonad`. Disabling this is an unsupported configuration, but it may be useful for accelerating builds in sandboxes for expert users. If disabled we will not supply instances of `Comonad`
containers	You can disable the use of the `containers` package using `-f-containers`. Disabing this is an unsupported configuration, but it may be useful for accelerating builds in sandboxes for expert users.
contravariant	You can disable the use of the `contravariant` package using `-f-contravariant`. Disabling this is an unsupported configuration, but it may be useful for accelerating builds in sandboxes for expert users. If disabled we will not supply instances of `Contravariant`
distributive	You can disable the use of the `distributive` package using `-f-distributive`. Disabling this is an unsupported configuration, but it may be useful for accelerating builds in sandboxes for expert users. If disabled we will not supply instances of `Distributive`
tagged	You can disable the use of the `tagged` package using `-f-tagged`. Disabing this is an unsupported configuration, but it may be useful for accelerating builds in sandboxes for expert users.

semigroups

binary	provide instances for binary package
bytestring	You can disable the use of the `bytestring` package using USE=-bytestring. Disabling this is an unsupported configuration, but it may be useful for accelerating builds in sandboxes for expert users.
containers	You can disable the use of the `containers` package using USE=-containers. Disabing this is an unsupported configuration, but it may be useful for accelerating builds in sandboxes for expert users.
deepseq	You can disable the use of the `deepseq` package using `-f-deepseq`. Disabing this is an unsupported configuration, but it may be useful for accelerating builds in sandboxes for expert users.
hashable	You can disable the use of the `hashable` package using USE=-hashable. Disabling this is an unsupported configuration, but it may be useful for accelerating builds in sandboxes for expert users. If set we will not supply an instance of `Hashable`.
text	You can disable the use of the `text` package using USE=-text. Disabling this is an unsupported configuration, but it may be useful for accelerating builds in sandboxes for expert users.
transformers	provide instances for transformers package.
unordered-containers	You can disable the use of the `unordered-containers` package using USE=-unordered-containers. Disabling this is an unsupported configuration, but it may be useful for accelerating builds in sandboxes for expert users.

sendfile

portable	Explicitly enable portable sendfile support (implemented in Haskell)

sha

exe	Build a sha1 and a sha384 executable similar to 'md5sum'.

shakespeare

test_coffee	Render tests through coffeescript render function.
test_export	Test export.
test_roy	Render tests through roy render function.

shakespeare-js

test_coffee	Test coffee.
test_export	Test export.
test_roy	Test roy.

shelly

lifted	run the tests against Shelly.Lifted

shuffle

network-uri	Get Network.URI from the network-uri package.

simple-sendfile

allow-bsd	Allow use of BSD sendfile (disable on GNU/kFreeBSD)

skein

big-endian	When manually selecting the endianness, use big-endian (default is little-endian).
force-endianness	Use a manually selected endian when compiling (see flag 'big-endian').
reference	Use the reference implementation instead of the optimized one.

skylighting

executable	Build the skylighting executable.

snap-core

portable	No non-haskell unportable code.

snap-server

build-pong	Build a server that just returns "PONG"
openssl	enable https support using dev-haskell/hsopenssl
portable	no non-haskell unportable code.

tagsoup

download	Build with Download module.
testprog	Build the test program.

tasty

colors	Enable colorful output

tasty-quickcheck

old-quickcheck	Use Quick-Check < 2.7.

texmath

executable	Compile test executable.
network-uri	Get Network.URI from the network-uri package.

text

developer	operate in developer mode

thyme

bug-for-bug	bug-for-bug compatibility with time
lens	use the full lens package
show-internal	instance Show of internal representation

tls

compat	Accept SSLv2 compatible handshake.
network	Use the base network library.

transformers-base

orphaninstances	Build instances for orphan datatypes.

transformers-compat

three	Use transformers-0.3

unix-compat

old-time	build against old-time package

uuagc

bootstrap_external	Use an external uuagc executable for bootstrapping.
with-loag	Use dev-haskell/minisat external SAT-solver to schedule all Linear Ordered AGs.

vector

boundschecks	Enable bounds checking
internalchecks	Enable internal consistency checks at the cost of a significant performance penalty
unsafechecks	Enable bounds checking in unsafe operations at the cost of a significant performance penalty

vector-algorithms

bench	Build a benchmarking program.
boundschecks	Enable bounds checking.
internalchecks	Enable internal consistency checks at the cost of a significant performance penalty.
properties	Enable quickcheck tests.
unsafechecks	Enable bounds checking in unsafe operations at the cost of a significant performance penalty.

void

safe	dissable effective but unsafe coersions

wai-app-static

print	print debug info.

warp

allow-sendfilefd	Allow use of sendfileFd (not available on GNU/kFreeBSD).
warp-debug	Add additional debuging information

x11

screensaver	whether to build XScreenSaver.

x509-store

executable	Build the executable

xss-sanitize

network-uri	Get Network.URI from the network-uri package.

yaml

no-examples	don't build the examples
no-exe	don't install the yaml2json executable
no-unicode	Don't enable unicode output. Instead, unicode characters will be escaped.
system-libyaml	Use system libyaml instead on generic one

yesod-auth

network-uri	Get Network.URI from the network-uri package

yesod-form

network-uri	Get Network.URI from the network-uri package

zip-archive

executable	Build the Zip executable.

zlib

non-blocking-ffi	Execute FFI calls in the context of haskell thread.

dev-java

ant

antlr	Enable ANTLR Ant tasks
bcel	Enable bcel (bytecode manipulation) Ant tasks
commonslogging	Enable commons-logging Ant tasks
commonsnet	Enable commons-net Ant tasks
jai	Enable JAI (Java Imaging) Ant task
javamail	Enable JavaMail Ant task
jdepend	Enable Jdepend Ant tasks
jmf	Enable JMF (Java Media Framework) Ant tasks
jsch	Disable Jsch (ssh, scp and related) Ant tasks
log4j	Enable Apache log4j Ant tasks
oro	Enable Apache Oro Ant tasks
regexp	Enable Apache Regexp Ant tasks
resolver	Enable Apache Resolver Ant tasks
testutil	Enable optional test util classes

commons-collections

test-framework	Install the test framework

commons-logging

avalon-framework	Add optional support for avalon-framework
avalon-logkit	Add optional support for avalon-logkit
log4j	Add optional support for log4j
servletapi	Add optional support for servletapi

ecj-gcj

native	Build a native binary along with the jar. Provides faster execution time, but needs about 1G memory and some patience to compile.

eclipse-ecj

ant	Support using ecj in Ant builds via dev-java/ant-eclipse-ecj

emma

launcher	Install /usr/bin/emma. Collides with sci-biology/emboss.

gcj-jdk

awt	Install AWT libraries, needed by some GUIs (not needed to build icedtea)

gnu-classpath

alsa	Build with ALSA javax.sound.midi provider
dssi	Build with DSSI javax.sound.midi provider
gconf	Build with GConf preferences backend
gjdoc	Build GJDoc, a documentation generator
gmp	Build with GMP backend for java.math.BigInteger
gstreamer	Build with GStreamer javax.sound.sampler provider
gtk	Build with Gtk+ AWT peers
qt4	Build with Qt4 AWT peers
xml	Build with native XML backend

icedtea

cacao	Use the CACAO virtual machine rather than HotSpot.
cups	Link against the CUPS library at compile time, rather than using it dynamically at runtime.
headless-awt	Don't install the X backend for AWT, needed by some GUIs (used to be X flag)
jamvm	Use the JamVM virtual machine rather than HotSpot.
jbootstrap	If possible, recompile the final IcedTea executables with itself.
nsplugin	Enable browser plugin (NPPlugin), requires also the webstart flag to be enabled.
nss	Enable NSS security provider support.
pax_kernel	Apply patch needed for pax enabled kernels.
shenandoah	Include the Shenandoah ultra-low pause time garbage collector (-XX:+UseShenandoahGC) (x86_64 only)
smartcard	Build the PCSC driver against pcsc-lite
sunec	Build the SunEC provider against system NSS
webstart	Enable Web Start support (via NetX).
zero	Enable Zero assembler port (usually for non-HotSpot architectures)

icedtea-bin

headless-awt	Don't install the X backend for AWT, needed by some GUIs (used to be X flag)
nss	Enable NSS security provider support
webstart	Provide javaws command through symlink to icedtea-web

icedtea-web

javascript	Enable support for using proxy auto config (PAC) files.
nsplugin	Enable the browser plugin (NPPlugin).
tagsoup	Depend on dev-java/tagsoup which allows parsing malformed .jnlp files

itext

rtf	Build and provide libraries for rich text format
rups	Build and provide GUI for Reading/Updating PDF Syntax

jcs

admin	Enable JCS Admin servlets

jdbc-jaybird

jni	Build/Install JDBC Type 2 native components

jdbc-mysql

c3p0	Enable c3p0 support
log4j	Enable log4 support

jfreesvg

debug	Enable debugging during compilation.

jna

awt	Enables support for Java AWT
nio-buffers	Enables support for NIO buffers

jython

readline	Use GNU readline instead of jline

log4j

javamail	Build the SMTPAppender
jms	Build the JMSAppender

logback

tomcat	Builds Apache Tomcat support

lucene

contrib	Include extra functionality from contrib/

miglayout

swt	Add support for the SWT toolkit.

netbeans-nb

keychain	Automatically starts keychain on netbeans start and loads specified keys so Netbeans can use them.

oracle-jdk-bin

commercial	Install features requiring a commercial license for production use
derby	Install bundled Derby (Java database)
headless-awt	Don't install the X backend for AWT, needed by some GUIs (used to be X flag)
javafx	Install JavaFX libraries
jce	Install Java Cryptographic Extension Unlimited Strength Jurisdiction Policy Files
source	Install JVM (and optionally JavaFX) sources
visualvm	Install VisualVM debugging tool

oracle-jre-bin

commercial	Install features requiring a commercial license for production use
headless-awt	Don't install the X backend for AWT, needed by some GUIs (used to be X flag)
javafx	Install JavaFX libraries
jce	Install Java Cryptographic Extension Unlimited Strength Jurisdiction Policy Files

proguard

ant	Ant task for using ProGuard in build.xml scripts
j2me	Adds support for J2ME Wireless Toolkit

protobuf-java

nano	Enable code generator and runtime library designed specifically for resource-constrained systems, like Android

rxtx

lfd	Installs and uses LockFileServer daemon (lfd)

sbt

binary	Install from (Gentoo-compiled) binary instead of building from sources. Set this when you run out of memory during build.

swt

webkit	Embedded browser support via net-libs/webkit-gtk:2, replacing former xulrunner-based browser.

dev-lang

bas

lr0	Use the LR0 parser instead of the recursive descending parser

crystal

blocking-stdio-hack	Keep STDIO file descriptors in blocking mode.
debug	Build each module as a separate object file. Speeds build up.
xml	Use the dev-libs/libxml2 library to enable Crystal xml module
yaml	Use the dev-libs/libyaml library to enable Crystal yaml module

ekopath

mpich	Include pre-built MPICH libraries
openmpi	Include pre-built OpenMPI 1.x libraries
openmpi2	Include pre-built OpenMPI 2.x libraries

erlang

compat-ethread	Enable compatibility with pre-pentium 4 CPUs in the ethread library.
dirty-schedulers	Enable dirty schedulers
halfword	Enable halfword emulator
hipe	HIgh Performance Erlang extension
kpoll	Enable kernel polling support

fpc

ide	Build and install the Free Pascal Compiler IDE

gdl

eigen	Build matrix manipulation with dev-cpp/eigen
grib	Add support for the meteorological GRIB format with sci-libs/grib_api
gshhs	Add support for projection adn continent maps with sci-geosciences/gshhs-data
hdf	Add support for the Hierarchical Data Format v.4
proj	Add support for sci-libs/proj (geographic projections)
udunits	Add support for manipulating units of physical quantities

ghc

binary	Install the binary version directly, rather than using it to build the source version.
ghcbootstrap	Bootstrap from an existing GHC installation.
ghcmakebinary	Build with less runtime depends (bundle libffi for building bootstrap binaries).

gnat-gcc

acats	Installs ACATS source under LIBPATH.

gnat-gpl

awt	Useful only when building GCJ, this enables Abstract Window Toolkit (AWT) peer support on top of GTK+
cilk	Support the Cilk Plus language (C/C++ based languages for parallel programming)
fixed-point	Enable fixed-point arithmetic support for MIPS targets in gcc (Warning: significantly increases compile time!)
go	Build the GCC Go language frontend.
graphite	Add support for the framework for loop optimizations based on a polyhedral intermediate representation
libssp	Build SSP support into a dedicated library rather than use the code in the C library (DO NOT ENABLE THIS IF YOU DON'T KNOW WHAT IT DOES)
mpx	Enable support for Intel Memory Protection Extensions (MPX)
nopie	Disable PIE support (NOT FOR GENERAL USE)
nossp	Disable SSP support (NOT FOR GENERAL USE)
objc	Build support for the Objective C code language
objc++	Build support for the Objective C++ language
objc-gc	Build support for the Objective C code language Garbage Collector
regression-test	Run the testsuite and install the results (requires FEATURES=test)
sanitize	Build support for various sanitizer functions (ASAN/TSAN/etc...)
ssp	Build packages with stack smashing protector on by default
vtv	Build support for virtual table verification (a C++ hardening feature)

go

gccgo	Enable bootstrapping using gccgo

icon

iplsrc	install the icon programming library source

lazarus

minimal	Don't build extra packages from the bigide component

logtalk

fop	Support for generating pdf documentation using fop
gnupl	Support GNU Prolog back-end compiler
qupl	Support Qu-Prolog back-end compiler
swipl	Support SWI-Prolog back-end compiler
xsbpl	Support XSB back-end compiler
xslt	Support for generating html documentation using xslt
yappl	Support YAP back-end compiler

lua

deprecated	make deprecated data structures/routines available

luajit

lua52compat	Enable some upwards-compatible features from Lua 5.2 that are unlikely to break existing code.

mercury

erlang	Support Mercury Erlang grade

mlton

binary	install a binary version (need to do this once to bootstrap, until smlnj is supported)

moarvm

asan	Enable clang's Address Sanitizer functionality. Expect longer compile time.
clang	Use clang compiler instead of GCC
jit	Enable Just-In-Time-Compiler. Has no effect except on AMD64 and Darwin.
optimize	Enable optimization via CFLAGS
ubsan	Enable clang's Undefined Behavior Sanitizer functionality. Expect longer compile time.

mono

pax_kernel	Enable if the user plans to run the package under a pax enabled hardened kernel
xen	Make mono generate code that is considerably faster on xen VMs but slightly slower on for normal systems.

nqp

clang	Toggle usage of the clang compiler in conjunction with MoarVM
moar	Build the MoarVM backend (experimental/broken)

ocaml

flambda	Enables the Flambda optimizer: A new intermediate representation (introduced in ocaml 4.03) in the depths of the compiler designed to allow for better inlining.
spacetime	Enables the Spacetime memory profiler. See https://caml.inria.fr/pub/docs/manual-ocaml/spacetime.html for more information.

orc

pax_kernel	Apply patch needed for pax enabled kernels.

perl

ithreads	Enable Perl threads, has some compatibility problems

php

cli	Enable CLI SAPI
coverage	Include gcov symbols for test coverage and lcov reports. Only useful for extension developers, and requires GCC.
embed	Enable embed SAPI
enchant	Add supports Enchant spelling library.
fileinfo	Add fileinfo extension support
filter	Add filter extension support
fpm	Enable the FastCGI Process Manager SAPI
gd	Adds support for gd (bundled with PHP)
hash	Enable the hash extension
intl	Enables the intl extension for extended internalization support
json	Enable JSON support
ldap-sasl	Add SASL support for the PHP LDAP extension
libmysqlclient	Use libmyslclient driver for mysql, mysqli, PDO_Mysql (not recommended)
opcache	Enables built-in opcode cache, replacing pecl-apc et al.
pdo	Enable the bundled PDO extensions
phar	Enables the phar extension to provide phar archive support
phpdbg	Enable the PHP Debug Command Line SAPI (like gdb for php)
vpx	Enable webp support for GD in php-5.x
webp	Enable webp support for GD in php-7.x
xmlreader	Enable XMLReader support
xmlwriter	Enable XMLWriter support
xslt	Enable the XSL extension
zip	Enable ZIP file support

polyml

portable	Build the portable interpreter version of Poly/ML instead of native.

python

threads	Enable threading support. (DON'T DISABLE THIS UNLESS YOU KNOW WHAT YOU'RE DOING)
wide-unicode	Enable wide Unicode implementation which uses 4-byte Unicode characters. Switching of this USE flag changes ABI of Python and requires reinstallation of many Python modules. (DON'T DISABLE THIS UNLESS YOU KNOW WHAT YOU'RE DOING)
wininst	Install Windows executables required to create an executable installer for MS Windows.

qu-prolog

pedro	Pedro subscription/notification communications system

rakudo

clang	Use Clang to compile the MoarVM backend
moar	Use the MoarVM as backend

rubinius

llvm	Build with llvm. Currently the package only builds against old versions of llvm.

ruby

jemalloc	Use dev-libs/jemalloc for memory allocation.
rdoc	Install dev-ruby/rdoc after installing Ruby.
readline	Use the sys-libs/readline library to provide the readline extension, used for instance by the irb tool. This flag is meaningful only if the libedit USE flag is disabled. If neither libedit nor readline USE flags are enabled, the readline extension will not be built (and irb will lose line editing functionality).
rubytests	Install ruby tests that can only be run after ruby is installed

rust

clang	Use sys-devel/clang for building
libcxx	Use sys-libs/libcxx as standard library when building with sys-devel/clang
system-llvm	Use system sys-devel/llvm in place of the bundled one

scala

binary	Install from (Gentoo-compiled) binary instead of building from sources. Set this when you run out of memory during build.

spidermonkey

custom-optimization	Build with user-specified compiler optimizations (-Os, -O0, -O1, -O2, -O3) from CFLAGS (unsupported)
debug	Enable assertions to allow for easier debugging of programs that link to spidermonkey -- note this will often crash software on regular end-user systems
system-icu	Use the system-wide dev-libs/icu instead of bundled -- note, only takes effect when icu flag is enabled
threadsafe	Build a threadsafe version of spidermonkey

swi-prolog

archive	Use libarchive for extension packs
uuid	Use ossp-uuid for UUID pack

swig

ccache	build ccache-swig(a fast compiler cache)

yap

R	Enable support for connecting R to Prolog

dev-libs

DirectFB

bmp	build BMP image provider
divine	enable DiVine
drmkms	build with DRM/KMS support
dynload	enable dynload support
egl	build with EGL support
fusiondale	enable FusionDale
fusionsound	enable FusionSound
gles2	build gles2 gfxdriver
imlib2	build Imlib2 image provider
input_hub	provides an asynchronous interface to the input devices available and those being added/removed
mpeg2	build MPEG2 image provider
mpeg3	build Libmpeg3 video provider
multicore	enable multicore support
pnm	build PNM (PBM/PGM/PPM) image provider
sawman	enable SaWMan (window manager and application manager)
swfdec	build Swfdec (Flash decoder) video provider
tremor	build Ogg/Vorbis music provider using Tremor
webp	build WebP image provider

ace

ciao	Include Component Intergraced Ace ORB into the build of ace
tao	Include the ACE ORB (CORBA stuff) (called tao) into the build of ace

actor-framework

benchmarks	Due to the number of out-of-tree deps, these only get installed as docs
boost	Make use of Boost's ASIO functionality
cash	Build the C Actor Shell for introspection and debugging
debug	Raises log-level to DEBUG, enables runtime checks and address sanitizer
doc	Compiles and installs the documentation as PDF and HTML
examples	Installs the provided example source files
mem_management	Enables built-in memory management
nexus	Nexus is the central component for CAF's runtime inspection
opencl	Compiles against the provided opencl implementation
riac	Runtime inspection and configuration
static	Provides a static build
test	Builds the provided unit tests

antlr-c

debugger	Compiles debug info into the library

appstream

apt	Enables Debians APT support

appstream-glib

stemmer	Add word stemming via dev-libs/snowball-stemmer.

apr

older-kernels-compatibility	Enable binary compatibility with older kernels
urandom	Use /dev/urandom instead of /dev/random

apr-util

libressl	Use dev-libs/libressl instead of dev-libs/openssl for 'openssl' USE flag
nss	Install apr_crypto_nss module
openssl	Install apr_crypto_openssl module

beignet

ocl-icd	Enable compatibility with the dev-libs/ocl-icd OpenCL ICD loader
ocl20	Enable experimental OpenCL 2.0 support on Skylake and newer architectures

bitset

jemalloc	Use dev-libs/jemalloc for allocations
tcmalloc	Use tcmalloc from dev-util/google-perftools for allocations

blitz

boost	Enable usage of boost::serialization

boost

context	Build and install the Boost.Context (and Boost.Fiber) library and all other Boost libraries that depend on it
debug	Build and install only the debug version of the Boost libraries. Only enable this flag if you're developing against boost.
doc	Install the full API documentation documentation. This takes over 200MB of extra disk space.
nls	Build libboost_locale. This library requires compatible C library interfaces, which might not be provided by uClibc or other embedded libraries.
threads	Build multi-thread-compatible libraries instead of single-threaded only.
tools	Build and install the boost tools (bcp, quickbook, inspect, wave)

botan

boost	use dev-libs/boost

c-blosc

lz4	Enable lz4 compression
snappy	Enable snappy compression
zstd	Enable zstd compression

check

subunit	Enable support for the subunit unit test protocol

cyberjack

fox	Enable installation of x11-libs/fox based fxcyberjack program

cyrus-sasl

authdaemond	Add Courier-IMAP authdaemond unix socket support (net-mail/courier-imap, mail-mta/courier)
ldapdb	Enable ldapdb plugin
openldap	Add ldap support for saslauthd
sample	Enable sample client and server
srp	Enable SRP authentication
urandom	Use /dev/urandom instead of /dev/random

dbus-c++

ecore	Use Ecore integration
glib	Use glib integration

efl

bmp	Enable WBMP image loader
drm	Enable DRM engine
eet	Enable Eet image loader
egl	Enable EGL rendering
fribidi	Enable bidirectional text support
gles	Enable the OpenGL ES GL implementation
glib	Enable dev-libs/glib support
harfbuzz	Enable complex text shaping and layout support
ibus	Enable Intelligent Input Bus
ico	Enable Ico image loader
oldlua	USE dev-lang/lua instead of dev-lang/luajit
physics	Enable Bullet physics effects and support
pixman	Enable PixMan for software rendering
ppm	Enable PMAPS image loader
psd	Enable PSD image loader
scim	Enable Smart Common Input Method
tga	Enable Tga image loader
tslib	Enable x11-libs/tslib for touchscreen events
unwind	Enable debug support via sys-libs/libunwind
valgrind	Enable usage of dev-util/valgrind in debug
webp	Enable WebP image loader
xim	Enable X Input Method

elfutils

lzma	Support automatic decompression of LZMA-compressed files and kernel images
threads	Build the libraries with thread safe support
utils	Install command-line utilities (all the eu-* programs)

fcgi

html	Install HTML documentation

folks

telepathy	Load contacts from the Telepathy framework
tracker	Load contacts from app-misc/tracker index
utils	Build the folks-inspect utility
zeitgeist	Add support for Zeitgeist event tracking system

fstrm

utils	Build fstrm utility programs

gecode

gist	Enable Gist, the Gecode Interactive Search Tool
gmp	Enable trigonometric and transcendental float constraints

gf2x

bindist	Disable automatic fine-tuning to local processor features like pclmul or sse2.

glib

dbus	Enable dependencies required by glib libraries using dbus service to manage settings saving
mime	Pull in shared MIME database that many glib-based applications require at runtime to detect or open files. Warning: do not disable this flag unless installing on a headless server.
systemtap	Build support for profiling and tracing using dev-util/systemtap
utils	Install gtester-report utility to generate test report files for your software; build gresource utility with ELF support.

gmime

smime	Enable experimental S/MIME support

gmp

asm	Enable use of hand optimized assembly routines (faster execution)
pgo	After building gmp, run some tests against to produce faster libraries -- this option will double the compile time

gobject-introspection

doctool	Install g-ir-doc-tool for generating documentation from introspected data

hidapi

fox	Build a x11-libs/fox GUI

intel-common

compiler	Install the libraries needed for the icc and ifort compilers

jemalloc

stats	Enable statistics calculation/reporting

kreport

marble	Enable displaying of maps using kde-apps/marble
scripting	Support Qml scripting using dev-qt/qtdeclarative

leveldb

snappy	support the snappy compression library

libRocket

samples	Build samples

libbase58

tools	Build command line base58 tool

libburn

cdio	Enable EXPERIMENTAL use of libcdio as system adapter
track-src-odirect	Read track input with O_DIRECT (see man 2 open), this may deliver a better write performance in some situations

libcdio

minimal	Only build the libcdio library and little more, just to be used to link against from multimedia players. With this USE flag enabled, none of the command-line utilities are built, nor is the CDDA library.

libcec

cubox	Enable support for enable support for the TDA995x
exynos	Enable support for Exynos chipsets
raspberry-pi	Enable support for the Raspberry Pi
xrandr	Enable detection of active HDMI using xrandr extensions

libcgroup

daemon	Install the configuration tools and init/config files.
tools	Install the cgroup rules processing daemon and init/config files.

libclsync

extra-debug	Enable extra debugging. This will hurt performance badly. Be ready for tons of output.
extra-hardened	Enable extra security checks. This may hurt performance.

libdbusmenu

gtk	Enable support for GTK+2
gtk3	Enable support for GTK+3

libdivecomputer

tools	Install tools that can be used to test the library.

libdynd

cuda	Enable NVIDIA CUDA toolkit support
mkl	Enable a plugin for Intel Math Kernel Library sci-libs/mkl

libevent

debug	Support runtime debug mode and malloc hooks (for programmers)

libffi

pax_kernel	Use PaX emulated trampolines, for we can't use PROT_EXEC

libflatarray

cuda	Enables plugins for NVIDIA GPUs (e.g. CUDAAllocator)

libgdata

gnome-online-accounts	Enable net-libs/gnome-online-accounts support

libgit2

gssapi	Enable GSSAPI support for SPNEGO auth
ssh	Enable SSH transport support
trace	Enable tracing support

libgit2-glib

ssh	Enable SSH transport support

libgpg-error

common-lisp	Install common-lisp files

libgpuarray

cuda	Enable NVIDIA CUDA toolkit support
opencl	Enable OpenCL support

libgweather

glade	Installs catalog files for dev-util/glade

libisoburn

cdio	Enable EXPERIMENTAL use of libcdio as system adapter
external-filters	Allow the use of external processes as file content filters (Note: this is a potential security risk)
external-filters-setuid	Also allow the use of external setuid processes as file content filters (Note: this is a potential security risk)
frontend-optional	Use dev-tcltk/bwidget which is not strictly required for the frontend
launch-frontend	Enable the tcl gui for xorriso
launch-frontend-setuid	Enable the tcl gui for xorriso under setuid

libisofs

verbose-debug	Enable verbose debug messages

libjit

interpreter	Enable the libjit interpreter
long-double	Enable the use of long double for jit_nfloat

liblogging

rfc3195	Enables RFC 3195 protocol (aka syslog-reliable) support. If you don't know what this is, you don't need it!
stdlog	Enables liblogging's core component (think of it as a the next version of the syslog(3) API).

libmail

apop	Enables the APOP authentication method

libmateweather

gtk3	Build with GTK+3 instead of GTK+2

libmemcached

hsieh	Use Hsieh hash algorithm.
libevent	Use the libevent event loop interface.
sasl	Use sasl auth for communications.

libnfc

pcsc-lite	Enable NFC drivers that require pcsc-lite

libnl

doc	Install development documentation
python	Install experimental dev-lang/python bindings
utils	Install command line interface utils

liborcus

spreadsheet-model	Enable the spreadsheet model implementation
tools	Build various low-level parsers

libowfat

diet	Compile against dev-libs/dietlibc

libp11

doc	Generate and install API documentation for the package.

libpcre

bzip2	Add support for pcregrep command to search within bzip2-compressed files (via app-arch/bzip2).
pcre16	Build PCRE library for 16 bit characters (e.g. UTF-16).
pcre32	Build PCRE library for 32 bit characters (e.g. UTF-32).
readline	Add support for command line editing to pcretest, through sys-libs/readline.
recursion-limit	Limit match recursion to 8192; if disabled, the default limit is used, which is the same as the match limit.
zlib	Add support for pcregrep command to search within gzip-compressed files (via sys-libs/zlib).

libpcre2

bzip2	Add support for pcregrep command to search within bzip2-compressed files (via app-arch/bzip2).
pcre16	Build PCRE library for 16 bit characters (e.g. UTF-16).
pcre32	Build PCRE library for 32 bit characters (e.g. UTF-32).
readline	Add support for command line editing to pcretest, through sys-libs/readline.
recursion-limit	Limit match recursion to 8192; if disabled, the default limit is used, which is the same as the match limit.
zlib	Add support for pcregrep command to search within gzip-compressed files (via sys-libs/zlib).

libpeas

glade	Install the glade catalog
python	Build support for loading dev-lang/python plugins

librdkafka

lz4	Enable support for Kafka's LZ4 compression based on KIP-57 (uses app-arch/lz4)

libressl

asm	Enables assembly

libsecp256k1

asm	Enable x86_64 assembly optimisation
ecdh	Enable ECDH shared secret computation
endomorphism	Enable endomorphism
experimental	Allow experimental USE flags
recovery	Enable ECDSA pubkey recovery module
schnorr	Enable Schnorr signature module
test_openssl	Enable OpenSSL comparison tests

libslz

tools	Install additional tools (zenc, zdec)

libsodium

asm	Enables assembly implementations
urandom	Use /dev/urandom instead of /dev/random

libsolv

rpm	Enable support for RPM files

libsqlora8

orathreads	Use Oracle threads

libtasn1

valgrind	Enable usage of dev-util/valgrind in debug

libtermkey

demos	Install demos, which pulls in dev-libs/glib

libucl

regex	Enable regex checking for schema
signatures	Enable signatures check
urlfetch	Enable URLs fetch
utils	Install the chargen and objdump utilities

libverto

glib	Support event loops using dev-libs/glib
libev	Support event loops using dev-libs/libev
libevent	Support event loops using dev-libs/libevent
tevent	Support event loops using sys-libs/tevent

link-grammar

aspell	Adds support for app-text/aspell spell checker
hunspell	Adds support for app-text/hunspell spell checker

log4cplus

iconv	Use inconv for wchar_t <-> char conversions. See also log4cplus's unicode.txt documentation
working-c-locale	Use the C99 locale facilities for wchar_t <-> char conversions. See also log4cplus's unicode.txt documentation
working-locale	Use C++'s std::locale for wchar_t <-> char conversions. See also log4cplus's unicode.txt documentation

log4cxx

smtp	Offer SMTP support via net-libs/libesmtp

m17n-lib

X	Builds the Graphical User Interface API and utilities for the package.
anthy	Enable support for app-i18n/anthy input method.
athena	Enable the MIT Athena widget set (x11-libs/libXaw)
gd	Build API and utilities based on media-libs/gd. This flag is only meaningful if the X USE flag is also enabled.
libotf	Use dev-libs/libotf to handle OpenType fonts
libxml2	Use dev-libs/libxml2 to parse XML

nss

cacert	Include root/class3 certs from CAcert (http://www.cacert.org/)
nss-pem	Add support for libnsspem
utils	Install utilities included with the library

oniguruma

combination-explosion-check	enable combination explosion check
crnl-as-line-terminator	enable CR+NL as line terminator

opencryptoki

tpm	Enable support for Trusted Platform Module (TPM) using app-crypt/trousers

openct

debug	Add debug output to the driver library for pcsc-lite.
pcsc-lite	Build a driver library for sys-apps/pcsc-lite, providing PC/SC API access to devices supported by OpenCT.
udev	Install rules for sys-fs/udev to auto-start openct.

openobex

irda	Enable IrDA support

opensc

ctapi	Use CT-API for accessing Smartcard hardware.
openct	Use dev-libs/openct (and CT-API) for accessing Smartcard hardware.
pcsc-lite	Use sys-apps/pcsc-lite (and PC/SC API) for accessing Smartcard hardware.
secure-messaging	Enable secure messaging.

openssl

asm	Support assembly hand optimized crypto functions (i.e. faster run time)
bindist	Disable EC algorithms (as they seem to be patented) -- note: changes the ABI
rfc3779	Enable support for RFC 3779 (X.509 Extensions for IP Addresses and AS Identifiers)
sslv2	Support for the old/insecure SSLv2 protocol -- note: not required for TLS/https
sslv3	Support for the old/insecure SSLv3 protocol -- note: not required for TLS/https
tls-heartbeat	Enable the Heartbeat Extension in TLS and DTLS

pkcs11-helper

nss	Enable NSS crypto engine

poco

7z	Add Support for the 7z archive format
apache	Enable support to write Apache modules using POCO
cppparser	Build and install a minimal C++ parser
crypto	Encryption and digital signing classes
data	Database abstraction layer to easily send/retrieve data to/from various databases
file2pagecompiler	Utility to convert ordinary files to Page Compiler source files
json	Add JSON support
mongodb	Add dev-db/mongodb support
net	Classes to write network clients & servers
pagecompiler	Simple compiler translating HTML pages containing embedded C++ code into HTTPRequestHandler classes
pocodoc	POCO documentation generator
util	Several utility classes (like logger, timer, config file parser)
zip	Add support for the zip & gz archive formats

ppl

lpsol	Build the ppl_lpsol linear programming problem solver

protobuf

java	Builds the Java implementation. This is not needed for Java support in protoc.
python	Builds the Python implementation. This is not needed for Python support in protoc.

softhsm

migration-tool	Build db migration tool

starpu

cuda	Enable NVIDIA CUDA toolkit support
gcc-plugin	Enable GCC extension plugin (experimental)
opencl	Enable OpenCL support

sway

gdk-pixbuf	Enable additional image format support via the x11-libs/gdk-pixbuf library.
swaybar	Build 'swaybar': sway's status bar component.
swaybg	Build 'swaybg': allows to set a desktop background image.
swaygrab	Build 'swaygrab': allows taking screenshots or screencasts.
swaylock	Build 'swaylock': sway's screen locker.
swaymsg	Build 'swaymsg': tool for communicating with a running sway instance.
wallpapers	Install sway's default wallpaper image.

tinyxml

stl	Compile with TIXML_USE_STL support

tntnet

server	Enable tntnet server daemon

totem-pl-parser

archive	Enables support for accessing media files in archives transparently via app-arch/libarchive
quvi	Use media-libs/libquvi for parsing video links

ucommon

socks	Build with socks proxy support

userspace-rcu

regression-test	Run regression tests (requires FEATURES=test)

ustr

ustr-import	Install ustr-import developer program and source code for bundling.

weston

colord	Allow setting color managment
drm	Enable drm compositor support
editor	Install wayland-editor example application
fbdev	Enable fbdev compositor support
gles2	Use GLESv2 cairo instead of full GL
headless	Headless backend and a noop renderer, mainly for testing purposes
ivi	Enable the IVI shell
launch	Install weston-launch utility
rdp	Enable Remote Desktop Protocol compositor support
resize-optimization	Increase performance, allocate more RAM. Recommended to disable on Raspberry Pi
rpi	Raspberry Pi GPU support
screen-sharing	Enable screen-sharing through RDP
unwind	Enable libunwind usage for backtraces
wayland-compositor	Enable Wayland compositor support
webp	Add support for the WebP image format
xwayland	Enable ability support native X11 applications

wlc

X	Enable X11 backend and XWayland support.
systemd	Enable support for systemd-logind.
xwayland	Enable XWayland support.

xapian

brass	Enabled brass backend db support
chert	Enabled chert backend db support
glass	Enabled glass backend db support
inmemory	Enabled inmemory backend db support

xerces-c

iconv	Use iconv (virtual/libiconv) as message loader and transcoder (in general it would be possible to use iconv only as message loader and something else like icu or the native method as transcoder and vice-versa, but this is a less common case and hard to handle)
threads	Enable threading support through pthread (or other libraries on AIX, IRIX, HPUX, Solars). Highly recommended

xml-security-c

nss	Use dev-libs/nss for certain crypto operations (configureable at runtime)
xalan	Enable support for XSLT and XPath parsing by dev-libs/xalan-c

xmlrpc-c

abyss	Build the Abyss mini web-server.
libxml2	Use dev-libs/libxml2 to parse XML instead of the internal expat library.
threads	Controls whether to build the Abyss web-server with pthreads or fork 'threading'.
tools	Build the xmlrpc* tools.

xmlsec

gcrypt	Install xmlsec-gcrypt library
gnutls	Install xmlsec-gnutls library
nss	Install xmlsec-nss library
openssl	Install xmlsec-openssl library

xqilla

faxpp	Use dev-libs/faxpp instead of Xerces-C for certain tasks
htmltidy	Use app-text/htmltidy when parsing HTML

yaz

ziffy	Install ziffy, a promiscuous Z39.50 APDU sniffer

dev-lisp

abcl

clisp	Build Armed Bear Common Lisp using GNU CLISP
cmucl	Build Armed Bear Common Lisp using CMU Common Lisp
jad	Enable support for disassembling compiled code using JAD

clisp

hyperspec	Use local hyperspec instead of online version
new-clx	Build CLISP with support for the NEW-CLX module which is a C binding to the Xorg libraries
pari	Build CLISP with support for the PARI Computer Algebra System
svm	Build CLISP with support for the Support Vector Machine module

clx

doc	Builds documentation

cmucl

source	Include source code for CMUCL in installation

ecls

gengc	Use generational garbage collection (experimental)
libatomic	Use dev-libs/libatomic_ops library
precisegc	Use type information during garbage collection (experimental)

gcl

ansi	Build a GCL with ANSI support (else build a traditional CLtL1 image)
athena	Build xgcl - an interface to x11-libs/libXaw

sbcl

pax_kernel	Enable if the user plans to run the package under a pax enabled hardened kernel

dev-lua

lpeg

luajit	Use dev-lang/luajit instead of dev-lang/lua

lua-openssl

luajit	Use dev-lang/luajit instead of dev-lang/lua

luafilesystem

luajit	Use dev-lang/luajit instead of dev-lang/lua

luaossl

luajit	Use dev-lang/luajit instead of dev-lang/lua

luarocks

curl	Uses net-misc/curl for fetching lua packages instead of net-misc/wget.
openssl	Uses dev-libs/openssl for verifying lua packages instead of md5sum.

luvit

bundled-libs	Use bundled versions of some libraries.

messagepack

luajit	Use the lua just-in-time compiler dev-lang/luajit instead of dev-lang/lua

mpack

luajit	Use dev-lang/luajit instead of dev-lang/lua

dev-ml

cairo-ocaml

pango	Enable support for x11-libs/pango

csv

lwt	Enables the Lwt-based library for asynchronous operations.

dose3

parmap	Adds multi-core CPU support via dev-ml/parmap.
rpm4	Adds support for handling rpm4 files.
zip	Adds support for handling zip files.

eliom

ppx	Enable PPX syntax extension support.

js_of_ocaml

deriving	Enable dev-ml/deriving support for improving the type safety.
ppx	Enables the ppx syntax extension
react	Enable functionnal reactive programming support.

lablgtk

glade	Enable libglade bindings compilation.
gnomecanvas	Enable libgnomecanvas bindings compilation.
sourceview	Enable GtkSourceView support

logs

cli	Enables the Logs_cli library that provides command line support for controlling Logs.
fmt	Enables the Logs_fmt reporter.
lwt	Enables the Logs_lwt library that provides Lwt logging functions.

lwt

camlp4	Enable camlp4 syntax extension
ppx	Enables the ppx syntax extension

ocaml-cohttp

async	Enables support for the dev-ml/async asynchronous execution library.
lwt	Enables support for the dev-ml/lwt cooperative light-weight thread library.

ocaml-cstruct

async	Support for asynchronous execution
lwt	Enable threads via lwt
ppx	Enable the ppx syntax extension

ocaml-dns

async	support for asynchronous execution
lwt	enable threads via lwt

ocaml-uri

allservices	Compile support for all service types

ocaml-websocket

async	Enables support for the dev-ml/async asynchronous execution library.
lwt	Enables support for the dev-ml/lwt cooperative light-weight thread library.

ocamlnet

httpd	Enables net-httpd web server component
zip	Enables netzip support to read/write gzip data using object channels

onanomsg

lwt	Enables lwt support.

pgocaml

camlp4	Enable PG'Ocaml syntax extension.

tyxml

camlp4	Enables the camlp4 syntax extension (deprecated)
ppx	Enables the ppx syntax extension (preferred)

uutf

utftrip	Builds and install the utftrip executable: Among other things, reads unicode on stdin and rewrites it on stdout.

zarith

mpir	Use MPIR library instead of GMP.

dev-perl

App-Nopaste

browser	Spawn browser with pasted page
clipboard	copying of URLs with -x/--copy
github	Github authentication
pastebin	pastebin.com support

Business-ISBN

barcode	Install dev-perl/GD-Barcode for rendering ISBN numbers as barcodes
xisbn	Install dev-perl/Mojolicious for querying xisbn.worldcat.org

Config-Any

conf	Install dev-perl/Config-General to support decoding .conf/.cnf files
ini	Install dev-perl/Config-Tiny to support decoding INI config files
json	Install support libraries to support decoding JSON config files
xml	Install support libraries to support decoding XML config files
yaml	Install support libraries to support decoding YAML config files

Convert-UUlib

system-uulib	Use dev-libs/uulib instead of bundled version.

Cookie-Baker

xs	Install dev-perl/Cookie-Baker-XS for accelerated performance

DBD-SQLite

system-sqlite	Use the system-wide dev-db/sqlite installation

DBD-mysql

embedded	Support embedded server (libmysqld)
ssl	Compile in support for SSL connections via libmysqlclient

DBIx-Class

admin	Modules required for the DBIx::Class administrative library
admin_script	Modules required for the CLI DBIx::Class interface dbicadmin
deploy	Modules required for "deploy" in DBIx::Class::Storage::DBI and "deploymen_statements" in DBIx::Class::Storage::DBI
replicated	Modules required for DBIx::Class::Storage::DBI::Replicated

File-HomeDir

xdg	Ensure XDG Semantics for returned paths via x11-misc/xdg-user-dirs

File-Which

pwhich	Install dev-perl/App-pwhich which used to be a part of this package

GD

animgif	Enable animated gif support
fcgi	Build for FastCGI compatibility via dev-libs/fcgi instead of using PerlIO

Graphics-ColorNames

recommended	Install recommended support modules

HTML-Mason

modperl	Enable www-apache/mod_perl support

HTTP-Entity-Parser

xs	Install C-Based dependieces for faster performance

JSON

xs	Install C-based dev-perl/JSON-XS for faster performance

JSON-MaybeXS

xs	Install a C-Based backend to make JSON encode/decode fast

Lab-Measurement

xpression	Install the Xpression measurement framework

List-MoreUtils

xs	Install C-Based backend implementation for performance

MCE

sereal	Install dev-perl/Sereal-Encoder and decoder for faster worker IPC

Mail-IMAPClient

md5	Install support for DIGEST-MD5 and CRAM-MD5 Authentication
ntlm	Install support for NTLM Authentication
ssl	Install support for SSL Connections
zlib	Install support for COMPRESS DEFLATE connections

Net-OpenSSH

sftp	Enable SFTP protocol support.

Net-SSH2

gcrypt	Use libgcrypt instead of openssl

PDL

badval	Enable bad values support
hdf	Enable HDF (version 4) format support
netpbm	Enable NETPBM and MPEG support
pdl2	Build pdf2 shell (requires Devel-REPL)
pgplot	Enable PGPLOT plotting capabilities

Panotools-Script

gui	Installs GUIs for some tools

Ref-Util

xs	Install C-Based dev-perl/Ref-Util-XS for accelerated performance

Sub-Name

suggested	Install extra dependencies needed for extended regression tests

Sysadm-Install

hammer	Enable hammer() funtion to run a command in the shell and simulate a user hammering the ENTER key to accept defaults on prompts

Test-Warnings

suggested	Install optional dependencies for extra tests

Text-CSV

xs	Install dev-perl/Text-CSV_XS for accelerated decoding

WWW-Form-UrlEncoded

xs	Install C-Based dependieces for faster performance

perl-headers

debug	Add source locations in generated .ph files to assist with debugging when errors occur
sizeof-warning	Include logic to warn when a .ph file tries to use a sizeof() that is unknown

dev-php

PEAR-HTTP_Download

minimal	Do not include support for PEAR-MIME_Type
postgres	Send postgres LOBs without buffering

PEAR-HTTP_Request2

curl	Force dev-lang/php to be compiled with curl extension
fileinfo	Force dev-lang/php to be compiled with fileinfo extension
ssl	Force dev-lang/php to be compiled with ssl extension
zlib	Force dev-lang/php to be compiled with zlib extension

PEAR-PHP_Beautifier

cli	Require dev-lang/php to be built with the "cli" SAPI and install the php_beautifier script.

ZendFramework

cli	Enables the CLI
doc	Installs the documentation
examples	Installs the examples
minimal	Installs the minimal version without Dojo toolkit, tests and demos

agavi

executable	Install the "agavi" executable used to manage projects. This requires dev-php/phing, and may be omitted if you are (for example) deploying an existing site to a production server.

pecl-apcu

lock_pthreadmutex	Enable pthread mutex locking
lock_pthreadrw	Enable pthread read/write locking
lock_semaphore	Enable semaphore locks instead of fcntl
lock_spinlock	Enable spin locks (EXPERIMENTAL)

pecl-event

extra	Add support of the Libevent extra API

pecl-memcached

igbinary	Enable support for the igbinary serializer
json	Enable support for json serialization

pecl-mysqlnd_qc

memcached	Use dev-libs/libmemcached as a storage handler
sqlite	Use dev-db/sqlite as a storage handler

pecl-redis

igbinary	Enables igbinary serialisation support

phing

zip	Support zip archives by requiring said support in dev-lang/php.

twig

extension	Build the C extension (only for php-5.6.x).

xcache

coverage	Enable the coverager module (not recommended for production servers).

dev-python

Kivy

camera	Install libraries needed to support camera
garden	Install garden tool to manage user maintained widgets

PyFoam

extras	Enable optional dependencies

PyQt4

X	Build bindings for the QtGui module
compat	Install the deprecated pyqtconfig module for backward compatibility
dbus	Build bindings for the QtDBus module
declarative	Build bindings for the QtDeclarative module
designer	Build bindings for the QtDesigner module and enable the designer plugin
help	Build bindings for the QtHelp module
kde	Select media-libs/phonon as Phonon variant (needed for KDE)
multimedia	Build bindings for the QtMultimedia module
opengl	Build bindings for the QtOpenGL module
phonon	Build bindings for the phonon module
script	Build bindings for the QtScript module
scripttools	Build bindings for the QtScriptTools module
sql	Build bindings for the QtSql module
svg	Build bindings for the QtSvg module
testlib	Build bindings for the QtTest module
webkit	Build bindings for the QtWebKit module
xmlpatterns	Build bindings for the QtXmlPatterns module

PyQt5

bluetooth	Build bindings for the QtBluetooth module
dbus	Build bindings for the QtDBus module
declarative	Build bindings for the QtQml/QtQuick modules and enable the qmlscene plugin
designer	Build bindings for the QtDesigner module and enable the designer plugin
gles2	Use GLES 2.0 or later instead of full OpenGL
gui	Build bindings for the QtGui module
help	Build bindings for the QtHelp module
location	Build bindings for the QtLocation module
multimedia	Build bindings for the QtMultimedia module
network	Build bindings for the QtNetwork module
opengl	Build bindings for the QtOpenGL module
positioning	Build bindings for the QtPositioning module
printsupport	Build bindings for the QtPrintSupport module
sensors	Build bindings for the QtSensors module
serialport	Build bindings for the QtSerialPort module
sql	Build bindings for the QtSql module
svg	Build bindings for the QtSvg module
testlib	Build bindings for the QtTest module
webchannel	Build bindings for the QtWebChannel module
webengine	Build bindings for the QtWebEngine module
webkit	Build bindings for the QtWebKit module
websockets	Build bindings for the QtWebSockets module
widgets	Build bindings for the QtWidgets module
x11extras	Build bindings for the QtX11Extras module
xmlpatterns	Build bindings for the QtXmlPatterns module

PythonQt

extensions	Install extensions

QtPy

designer	Build bindings for the QtDesigner module and enable the designer plugin
gui	Build bindings for the QtGui module
svg	Build bindings for the QtSvg module
testlib	Build bindings for the QtTest module
webkit	Build bindings for the QtWebKit module

amqplib

extras	Install extra tools to generate initial Python mod from an AMQP XML file

anyvc

bazaar	Add support for Bazaar
mercurial	Add support for Mercurial

cassandra-driver

cython	Optimize core modules and build custom extensions
libev	libev event loop integration
murmur	Faster hashing for token-aware routing

celery

redis	Enables redis support
sqs	Enables Amazon SQS transport module for celery
yaml	Enable support of yaml as a configuration file format
zeromq	Enable logging and deployment via ZeroMQ

cgkit

3ds	Enable support for importing 3D Studio models

cvxopt

dsdp	Use interior point library sci-libs/dsdp
glpk	Use GNU Linear Programming Kit sci-mathematics/glpk

dap

server	Enable OpenDAP server support

django-cms

admin-style	Install plugin customizing admin panel styles
ckeditor	Install text-ckeditor plugin for rich text editing
file	Install djangocms file plugin
flash	Install djangocms flash plugin
inherit	Install djangocms inherit plugin
link	Install djangocms link plugin
picture	Install djangocms picture plugin
snippet	Install djangocms snippet plugin
teaser	Install djangocms teaser plugin
video	Install djangocms video plugin

django-tastypie

bip	An optional serialiser dev-python/biplist
digest	Library to aid in implementing HTTP Digest Authentication
lxml	An optional serialiser dev-python/lxml
yaml	An optional serialiser dev-python/yaml

django-two-factor-auth

yubikey	Adds support for Yubikeys via django-otp-yubikey

editorconfig-core-py

cli	Install command line interface as well as python library

falcon

cython	Build cython-based python modules

flask-restful

paging	Enable resource paging support

geopy

timezone	Enables localized date support
yahoo	Enables use of YahooPlaceFinder

glance_store

cinder	adds cinder backend support

gmpy

mpir	Use sci-libs/mpir as gmp implementation

icalendar

doc	Generate examples and other extra documentation

ipython

matplotlib	Add support for dev-python/matplotlib
mongodb	Enable support for MongoDB via dev-python/pymongo
nbconvert	Enable support for converting notebooks to various formats using app-text/pandoc
notebook	Install requirements for the web notebook based on www-servers/tornado
octave	Enable octave bridge via dev-python/oct2py

jira

filemagic	Include filemagic support (for identifying uploaded filetypes)
ipython	Include Interactive Python (IPython)
oauth	Support OAuth authentication

kaa-base

tls	SSL/TLS support via dev-python/tlslite

kafka-python

snappy	Install snappy compression/decompression support

kazoo

gevent	Enable support for the gevent based handler

kombu

amqplib	Enable amqplib support
msgpack	Enables MessagePack (de)serializer for Python
sqs	Enables Amazon SQS transport module for Kombu

markdown

pygments	Enable fancy pygments support

matplotlib

excel	Pull dev-python/xlwt for the exceltools toolkit
gtk2	Enable x11-libs/gtk+:2 support
gtk3	Enable x11-libs/gtk+:3 support
pyside	Qt support via dev-python/pyside

mpmath

matplotlib	Add support for dev-python/matplotlib

nbdime

webtools	Install web-based diff and merge tools.

netaddr

cli	Enable netaddr shell with dev-python/ipython

nltk

numpy	Use numpy for the saved word tokenizer

numexpr

mkl	Enable support for Intel Vector Math Library, part of sci-libs/mkl.

pandas

R	Enable support for R via dev-python/rpy
excel	Pull a few Python packages for Microsoft Excel i/o
full-support	Pull all packages to give pandas full support
html	Enable HTML i/o via dev-python/beautifulsoup

passlib

bcrypt	bcrpyt hash algoryptm support
scrypt	accelerated scrypt algoythm support
totp	time based one time password support

paste

flup	enable support for flup (and therefore for various wgsi servers and middleware)
openid	enable OpenID support

pillow

webp	Enable support for webp image format.

py-amqp

extras	Install extra tools to generate initial Python mod from an AMQP XML file

pygame

midi	Enable midi support using media-libs/portmidi

pygpu

cuda	Enable NVIDIA CUDA toolkit support
opencl	Enable OpenCL support

pyhamcrest

numpy	Enable optional dependence on dev-python/numpy

pyocr

cuneiform	Enable support for the app-text/cuneiform OCR engine
tesseract	Enable support for the app-text/tesseract OCR engine

pypax

ptpax	Enable PT_PAX_FLAGS support.
xtpax	Enable XATTR_PAX_FLAGS support.

pyplusplus

indexing	Install indexing_suite_v2 to enhance boost python
numpy	Generate code for dev-libs/boost-numpy to accelerate arrays

pypy

low-memory	Build using PyPy with the engine configured towards low memory footprint. \ This makes it possible to build PyPy using ~3.5G of RAM on amd64 and ~half of that on x86, at the cost of lengthened build time. Please note that you will need an extra ~1G of extra RAM or \ swap since the translation memory (unused at the time) is not freed when the C compiler is spawned.
sandbox	Enable sandboxing functionality
shadowstack	Use a shadow stack for finding GC roots

pypy-bin

shadowstack	Use a shadow stack for finding GC roots

pypy3

low-memory	Build using PyPy with the engine configured towards low memory footprint. This makes it possible to build PyPy using ~3.5G of RAM on amd64 and ~half of that on x86, at the cost of lengthened build time. Please note that you will need an extra ~1G of extra RAM or swap since the translation memory (unused at the time) is not freed when the C compiler is spawned.
sandbox	Enable sandboxing functionality
shadowstack	Use a shadow stack for finding GC roots

pypy3-bin

shadowstack	Use a shadow stack for finding GC roots

pyside

X	Build QtGui and QtTest modules
declarative	Build QtDeclarative module
designer	Build QtDesigner and QtUiTools modules
help	Build QtHelp module
multimedia	Build QtMultimedia module
opengl	Build QtOpenGL module
phonon	Build phonon module
script	Build QtScript module
scripttools	Build QtScriptTools module
sql	Build QtSql module
svg	Build QtSvg module
webkit	Build QtWebKit module
xmlpatterns	Build QtXmlPatterns module

python-caja

gtk3	Build with GTK+3 instead of GTK+2

python-stdnum

vies	Enable VIES

pyudev

pygobject	Install PyGobject bindings
pyside	Install PySide bindings
qt4	Install PyQt4 bindings
qt5	Install PyQt5 bindings

pyyaml

libyaml	enable support for C implementation using libyaml

pyzmq

green	Enable gevent compatibility with zeromq

pyzor

gevent	Enable support for the gevent based handler
mysql	Enables mysql support
pyzord	enable support for pyzord
redis	Enables redis support

rarfile

compressed	Enables the module to support compressed v3 archives by calling the app-arch/unrar.

rdflib

redland	enable support for Redland triplestore

restkit

cli	Install the restcli command line interface/tool, based on dev-python/ipython

scrapy

boto	Add support for Amazon S3 via dev-python/boto
ibl	Use Instace Based Learning algorithm for automatic extraction

simplecv

shell	Enable the iPython SimpleCV shell

sphinx

net	enable internet capabilities

spyder

ipython	Add support for dev-python/ipython
matplotlib	Add support for dev-python/matplotlib
numpy	Add support for dev-python/numpy
pep8	Add support for dev-python/pep8
pyflakes	Add support for dev-python/pyflakes
pylint	Add support for dev-python/pylint
qtconsole	Add support for dev-python/qtconsole
rope	Add support for dev-python/rope
scipy	Add support for sci-libs/scipy
sphinx	Add support for dev-python/sphinx

starcluster

epydoc	Enable build of apidocs in html using epydoc

sympy

imaging	Add support for dev-python/pillow
ipython	Add support for dev-python/ipython
mathml	Add support for mathml
pyglet	Use dev-python/pyglet for plots and print preview
texmacs	Add app-office/texmacs interface
theano	Add support for dev-python/theano

tdaemon

coverage	Enable code coverage support

translate-toolkit

html	Support conversion between po and html files
ical	Support conversion between po and ical files
ini	Support conversion between po and ini files
subtitles	Support conversion between po and sub files
yaml	Support YAML format

twisted

conch	include Twisted SSHv2 implementation
http2	include http2 support
serial	include serial port support

twisted-core

serial	include serial port support

vatnumber

vies	Enable VIES

ws4py

client	Install client modules
server	Install server modules

wxpython

doc	Install HTML wxWidgets docs and wxpython API reference.
examples	Install interactive demo module browser and sample applets.

zeep

async	Add async support

zsi

twisted	add support for python-twisted (needs dev-python/twisted-core and dev-python/twisted-web)

dev-qt

assistant

exceptions	Add support for exceptions - like catching them inside the event loop (recommended by upstream)

designer

declarative	Build the qdeclarativeview plugin
exceptions	Add support for exceptions - like catching them inside the event loop (recommended by upstream)
phonon	Build the phononwidgets plugin
qt3support	Build the qt3supportwidgets plugin
webkit	Build the qwebview plugin

linguist

exceptions	Add support for exceptions - like catching them inside the event loop (recommended by upstream)

linguist-tools

qml	Enable QML support in lupdate

pixeltool

exceptions	Add support for exceptions - like catching them inside the event loop (recommended by upstream)

qdbusviewer

exceptions	Add support for exceptions - like catching them inside the event loop (recommended by upstream)

qt-creator

android	Build plugin for Android devices
autotools	Enable autotools project manager plugin
baremetal	Build plugin for bare metal devices
bazaar	Add support for dev-vcs/bzr version control system
clang	Build clang-based code model plugin
clangcodemodel	Build clang-based code model and refactoring plugins
clangstaticanalyzer	Build clang-based static analyzer plugin
clearcase	Add support for IBM ClearCase version control system (requires manual installation of ClearCase client)
cmake	Enable cmake project manager plugin
designer	Build widget designer plugin
glsl	Enable GLSL source code editor
ios	Build plugin for Apple iOS devices
mercurial	Add support for dev-vcs/mercurial version control system
modeling	Enable graphical model editor
nim	Enable Nim source code editor
perforce	Add support for Perforce version control system (requires manual installation of Perforce client)
python	Enable Python source code editor
qbs	Enable QBS project manager plugin
qnx	Build plugin for QNX devices
scxml	Enable graphical SCXML editor
systemd	Add support for retrieving application output from journald
valgrind	Add support for memory debugging using dev-util/valgrind
webengine	Use dev-qt/qtwebengine to view documentation
webkit	Use dev-qt/qtwebkit to view documentation
winrt	Build plugin for WinRT devices

qt-meta

kde	Select media-libs/phonon as Phonon variant (needed for KDE)
qt3support	Enable the Qt3Support library for Qt4

qt-mobility

bluetooth	Enable Bluetooth support in QtConnectivity and QtSystemInfo modules
connectivity	Build the QtConnectivity module
contacts	Build the QtContacts module
feedback	Build the QtFeedback module
gallery	Build the QtGallery module
location	Build the QtLocation module
messaging	Build the QtMessaging module
multimedia	Build the QtMultimediaKit module
networkmanager	Enable NetworkManager support in QtBearer and QtSystemInfo modules
organizer	Build the QtOrganizer module
publishsubscribe	Build the QtPublishSubscribe module
pulseaudio	Enable PulseAudio support in QtMultimediaKit module
qml	Build QML bindings
sensors	Build the QtSensors module
serviceframework	Build the QtServiceFramework module
systeminfo	Build the QtSystemInfo module
tools	Build various useful tools (e.g.: qcrmlgen, servicexmlgen, vsexplorer, ...)
versit	Build the QtVersit module

qt3d

gles2	Use GLES 2.0 or later instead of full OpenGL
qml	Build QML/QtQuick bindings

qt3support

exceptions	Add support for exceptions - like catching them inside the event loop (recommended by upstream)

qtbearer

exceptions	Add support for exceptions - like catching them inside the event loop (recommended by upstream)

qtbluetooth

qml	Build QML/QtQuick bindings and imports

qtcharts

qml	Build QML/QtQuick bindings and imports

qtcore

exceptions	Add support for exceptions - like catching them inside the event loop (recommended by upstream)
glib	Enable dev-libs/glib eventloop support
qt3support	Enable the Qt3Support libraries for Qt4. Note that this does not mean you can compile pure Qt3 programs with Qt4.
systemd	Enable native journald logging support

qtdatavis3d

gles2	Use GLES 2.0 or later instead of full OpenGL
qml	Build QML/QtQuick bindings and imports

qtdbus

exceptions	Add support for exceptions - like catching them inside the event loop (recommended by upstream)

qtdeclarative

exceptions	Add support for exceptions - like catching them inside the event loop (recommended by upstream)
gles2	Use GLES 2.0 or later instead of full OpenGL
localstorage	Build the LocalStorage import for QtQuick (requires QtSql)
qt3support	Enable the Qt3Support libraries for Qt4. Note that this does not mean you can compile pure Qt3 programs with Qt4.
webkit	Build the WebView QML component
widgets	Enable QtWidgets support
xml	Build the XmlListModel import for QtQuick (requires QtXmlPatterns)

qtdemo

dbus	Build QtDBus examples and demos
declarative	Build QtDeclarative examples and demos
exceptions	Add support for exceptions - like catching them inside the event loop (recommended by upstream)
multimedia	Build QtMultimedia examples and demos
opengl	Build QtOpenGL examples and demos
phonon	Build Phonon examples and demos
webkit	Build QtWebKit examples and demos
xmlpatterns	Build QtXmlPatterns examples and demos

qtgui

egl	Enable EGL integration
eglfs	Build the EGL Full Screen/Single Surface platform plugin
evdev	Enable support for input devices via evdev
exceptions	Add support for exceptions - like catching them inside the event loop (recommended by upstream)
gles2	Use GLES 2.0 or later instead of full OpenGL
glib	Enable integration with the dev-libs/glib event loop
gtkstyle	Build a widgets style that mimics the active GTK+ theme
ibus	Build the IBus input method plugin
libinput	Enable support for input devices via dev-libs/libinput
qt3support	Enable the Qt3Support libraries for Qt4. Note that this does not mean you can compile pure Qt3 programs with Qt4.
trace	Build the 'trace' graphicssystem engine which allows to record all drawing operations into a trace buffer. The trace can be replayed later with the qttracereplay tool.
tslib	Enable support for touchscreen devices via x11-libs/tslib
tuio	Build plugin to receive touch events over the TUIO protocol
xcb	Build the XCB platform plugin and enable X11 integration

qthelp

compat	Build the extra compatibility layer required by a few packages, see http://blog.qt.io/blog/2010/06/22/qt-assistant-compat-version-available-as-extra-source-package/
exceptions	Add support for exceptions - like catching them inside the event loop (recommended by upstream)

qtmultimedia

exceptions	Add support for exceptions - like catching them inside the event loop (recommended by upstream)
gles2	Use GLES 2.0 or later instead of full OpenGL
gstreamer	Enable audio support via media-libs/gstreamer using SLOT 1.0
gstreamer010	Enable audio support via media-libs/gstreamer using SLOT 0.10
qml	Build QML/QtQuick bindings and imports
widgets	Build the QtMultimediaWidgets module

qtnetwork

bindist	Disable EC support via dev-libs/openssl
connman	Enable net-misc/connman-based bearer plugin
libproxy	Use net-libs/libproxy for automatic HTTP/SOCKS proxy configuration
networkmanager	Enable net-misc/networkmanager-based bearer plugin

qtopengl

egl	Use EGL instead of GLX to manage OpenGL contexts
exceptions	Add support for exceptions - like catching them inside the event loop (recommended by upstream)
gles2	Use GLES 2.0 or later instead of full OpenGL
qt3support	Enable the Qt3Support libraries for Qt4

qtphonon

exceptions	Add support for exceptions - like catching them inside the event loop (recommended by upstream)
qt3support	Enable the Qt3Support libraries for Qt4. Note that this does not mean you can compile pure Qt3 programs with Qt4.

qtpositioning

geoclue	Use enhanced location information from app-misc/geoclue
qml	Build QML bindings

qtprintsupport

gles2	Use GLES 2.0 or later instead of full OpenGL

qtquickcontrols

widgets	Enable QtWidgets support

qtscript

exceptions	Add support for exceptions - like catching them inside the event loop (recommended by upstream)
scripttools	Build the QtScriptTools module (requires QtWidgets)

qtsensors

qml	Build QML bindings

qtsql

exceptions	Add support for exceptions - like catching them inside the event loop (recommended by upstream)
qt3support	Enable the Qt3Support libraries for Qt4

qtsvg

exceptions	Add support for exceptions - like catching them inside the event loop (recommended by upstream)

qttest

exceptions	Add support for exceptions - like catching them inside the event loop (recommended by upstream)

qtwayland

egl	Use EGL instead of GLX to manage OpenGL contexts
qml	Build QML/QtQuick bindings
wayland-compositor	Build Qt compositor for wayland

qtwebchannel

qml	Build QML/QtQuick bindings and imports

qtwebengine

geolocation	Enable physical position determination via dev-qt/qtpositioning
pax_kernel	Enable building under a PaX enabled kernel
system-ffmpeg	Use the system-wide media-video/ffmpeg instead of bundled.
system-icu	Use the system-wide dev-libs/icu instead of bundled.
widgets	Enable QtWidgets support

qtwebkit

exceptions	Add support for exceptions - like catching them inside the event loop (recommended by upstream)
geolocation	Enable physical position determination via dev-qt/qtpositioning
gstreamer	Enable HTML5 audio/video support via media-libs/gstreamer using SLOT 1.0
gstreamer010	Enable HTML5 audio/video support via media-libs/gstreamer using SLOT 0.10
multimedia	Enable HTML5 audio/video support via dev-qt/qtmultimedia
orientation	Enable device orientation detection via dev-qt/qtsensors
printsupport	Enable printing via dev-qt/qtprintsupport
qml	Build QML/QtQuick bindings
webchannel	Enable integration with dev-qt/qtwebchannel
webp	Add support for WebP image format

qtwebsockets

qml	Build QML bindings

qtwidgets

gles2	Use GLES 2.0 or later instead of full OpenGL
gtkstyle	Build a Qt style called GTK+ that mimics the active GTK+ theme

dev-ros

rosbag

lz4	Add support for lz4 compressed bags.

rosconsole

glog	Use dev-cpp/glog as log backend.
log4cxx	Use dev-libs/log4cxx as log backend.

dev-ruby

barby

cairo	Add support for writing images (PNG, PS, EPS and, if supported, PDF and SVG) using dev-ruby/rcairo. Not available on JRuby.
png	Add support for writing PNG images using dev-ruby/chunky_png.
prawn	Add support for writing PDF documents using dev-ruby/prawn.
qrcode	Add support for QRCode 2D codes using dev-ruby/rqrcode.
rmagick	Add support for writing images (among others PNG, GIF and JPEG) using dev-ruby/rmagick. Not available on JRuby.

facter

dmi	Use sys-apps/dmidecode to determine hardware system properties
pciutils	Use sys-apps/pciutils to determine hardware system properties
virt	Use app-emulation/virt-what for virtual machine detection

faraday_middleware

mashify	Include FaradayMiddleware::Mashify
oauth	Include FaradayMiddleware::OAuth
parsexml	Include FaradayMiddleware::ParseXml
rashify	Include FaradayMiddleware::Rashify

maruku

highlight	Enable source code highlighting via dev-ruby/syntax

net-ssh

sodium	Use dev-libs/libsodium via dev-ruby/rbnacl for Ed25519 support.

rails

asset-pipeline	Also install the default components for the asset pipeline. These are not required but they are activated automatically in new Rails projects by default.

rrdtool-bindings

graph	Enable support for graphing functions

rspec-core

highlight	Enable source code highlighting via dev-ruby/coderay

ruby-sdl

image	Enable media-libs/sdl-image support
mixer	Enable media-libs/sdl-mixer support
sge	Enable sdl-sge support

rubygems

server	Install support for the rubygems server

dev-scheme

gauche-gl

cg	Enable NVidia Cg binding

gauche-gtk

glgd	Enable GL graph draw

guile

debug-freelist	Include garbage collector freelist debugging code
debug-malloc	Include malloc debugging code
deprecated	Enable deprecated features
discouraged	(implied by deprecated) enable merely discouraged features
networking	Include networking interfaces
regex	Include regular expression interfaces

kawa

awt	Assume AWT is available
echo2	Enable support for the Echo2 web toolkit with dev-java/echo2
frontend	Build "kawa" front-end program using sys-libs/readline
jemacs	Build JEmacs
krl	Build BRL emulation and KRL
sax	Assume SAX2 is available with dev-java/sax
servlets	Build support for generating servlets with dev-java/servletapi
swing	Assume Swing is available
swt	Assume SWT is available with dev-java/swt
xqtests	Support XQuery Test Suite

racket

backtrace	Support GC backtrace dumps
futures	Enable racket/future library for fine-grained hardware parallelism
places	Enable racket/place library for share-nothing parallelism and message-passing communication. Compared to futures, places are heavyweight, but they have a simpler performance model.
plot	Enable plot libraries
threads	Enable support for green threads

scm

arrays	Support for arrays, uniform-arrays and uniform-vectors.
bignums	Support for large precision integers.
cautious	SCM will always check the number of arguments to interpreted closures.
dynamic-linking	Be able to load compiled files while running.
engineering-notation	Floats to display in engineering notation (exponents always multiples of 3) instead of scientific notation.
gsubr	generalized c arguments: for arbitrary (more then 11) arguments to C functions.
inexact	Support for floating point numbers.
ioext	Commonly available I/O extensions: line I/O, file positioning, file delete and rename, and directory functions.
libscm	Build and install libscm.a and related headers
macro	C level support for hygienic and referentially transparent macros (syntax-rules macros).
regex	String regular expression matching.
unix	Support for: nice, acct, lstat, readlink, symlink, mknod and sync.

slib

gambit	Support for gambit scheme implementation
scm	Support for scm scheme implementation

dev-tcltk

expect-lite

debug	pull in packages needed for runtime interactive debugger

tktreectrl

shellicon	shellicon extension

dev-tex

abntex

lyx	Install with app-office/lyx layout

biblatex

biber	Install the unicode compatible backend processor

circuit_macros

script	Install cm2pdf to automatically create a correctly sized PDF from a circuit_macro m4 source

dot2texi

pgf	Enable support for dev-tex/pgf (The TeX Portable Graphic Format)
pstricks	Enable pstricks support

dev-texlive

texlive-basic

luajittex	Add support for LuaJitTeX: LuaTeX based on LuaJIT which is usually faster.

dev-util

android-ndk

legacy-toolchains	Install legacy toolchains
target-32	Support for 32-bit targets
target-64	Support for 64-bit targets

anjuta

devhelp	Enable devhelp integration
glade	Build glade plugin for anjuta
packagekit	Use packagekit to search for missing tools
terminal	Enable terminal plugin based on x11-libs/vte

apitrace

cli	Enable command line interface
egl	Enable EGL support
system-snappy	Link dynamic against app-arch/snappy

bazel

tools	Install extra bazel tools to build from sources

bitcoin-tx

knots	Build enhanced Bitcoin Knots version, rather than Bitcoin Core
ljr	Enable Luke Dashjr's patches

buildbot

irc	Add support for status delivery through an ircbot.
mail	Add support for watching a maildir for commits.
manhole	Add support for manhole (debug over ssh)

bustle

interactivetests	Build interactive test programs
threaded	Build with support for multithreaded execution.

catalyst

ccache	Enables ccache support

cccc

apidoc	Build software docs with doxygen/graphviz and metrics with cccc
mfc	Add patch for MFC dialect options

cmake

server	Enable cmake-server support.
system-jsoncpp	Use system copy of dev-libs/jsoncpp instead of bundled one.

coccigrep

vim	Install the coccigrep vim plugin

codeblocks

contrib	Build additional contrib components

cppcheck

htmlreport	install cppcheck-htmlreport

ctags

ada	Enable Ada support
json	Enable JSON output support
xml	Enable XML parsing support
yaml	Enable YAML parsing support

cwdiff

a2ps	install app-text/a2ps for postscript output
mercurial	install hg wdiff alias for dev-vcs/mercurial

devhelp

gedit	Install plugin for app-editors/gedit

dialog

minimal	Disable library, install command-line program only

edb-debugger

graphviz	Add support for the Graphviz library
legacy-mem-write	Probe if writes to /proc/PID/mem are broken.
pax_kernel	Enable building under a PaX enabled kernel

electron

hidpi	Enable support for high-resolution screens (high dots per inch)
lto	Build with link time optimization enabled
pic	Disable optimized assembly code that is not PIC friendly
proprietary-codecs	Enable proprietary codecs like H.264, MP3
system-ffmpeg	Use system ffmpeg instead of the bundled one
tcmalloc	Use bundled tcmalloc instead of system malloc

emilpro

system-binutils	Use the gentoo binutils instead of building against an unpatched vanilla version

fatrace

powertop	Add powetop integration

geany

gtk3	Use GTK+3 instead of GTK+2
vte	Enable Terminal support (x11-libs/vte)

geany-plugins

autoclose	Enable the autoclose plugin.
automark	Enable the automark plugin
commander	Enable the commander plugin which provides a command panel for rapid access to any action.
ctags	Enable ctags plugin
debugger	Enable the debugger plugin which interfaces with sys-devel/gdb
defineformat	Enable the defineformat plugin.
enchant	Enable spell checking using enchant
gpg	Enable geanypg plugin which integrates GPG using app-crypt/gpgme
gtk3	Use GTK+3 instead of GTK+2
gtkspell	Use gtkspell for dictionary support in GeanyVC
multiterm	Enable the multiterm plugin
overview	Enable overview plugin
scope	Enable the scope plugin which is a graphical GDB front-end
soup	Enable updatechecker and geniuspaste plugins which require net-libs/libsoup

global

vim	Integrate the GNU GLOBAL source code tag system with Vim

google-perftools

debug	Build a set of libraries with debug support (so-called debugalloc). These are available by default but are not needed unless you're actually developing using tcmalloc.
largepages	Use (experimental) larger pages for tcmalloc, this increases memory usage, but should speed up the allocation/free operations.
minimal	Only build the tcmalloc_minimal library, ignoring the heap checker and the profilers.
optimisememory	To build libtcmalloc with smaller internal caches.

gtk-doc

highlight	Enable source code highlighting
vim	Enable source code highlighting through app-editors/vim

idea-community

custom-jdk	Install and use IntelliJ's custom JRE.

idea-ultimate

custom-jdk	Install and use IntelliJ's custom JRE.

intel-ocl-sdk

android	Install android related files
system-boost	Use system boost (dev-libs/boost) instead of bundled one
system-clang	Use system clang (sys-devel/clang) instead of bundled one
system-qt	Use system Qt (sys-devel-qtcore, sys-devel/qtgui) instead of bundled one
system-tbb	Use sytem Thread Building Blocks (dev-cpp/tbb) instead of bundled one
tools	Install Intel Offline Compiler

kdevelop

gdbui	Enable GUI for attaching GDB to a running process
ninja	Enable support for Ninja build system
okteta	Enable hex editor plugin
qmake	Enable support for QMake build system
qthelp	Enable support for QtHelp documentation browsing

kdevplatform

reviewboard	Enable reviewboard support
welcomepage	Enable welcome page, requires dev-qt/qtdeclarative

ltrace

unwind	Use sys-libs/libunwind for frame unwinding support

lttng-tools

ust	Support LTTng-UST (Userspace Tracing)

mdds

valgrind	Add support for memory debugging using dev-util/valgrind

mingw64-runtime

idl	Install idl files.
libraries	Build extra libraries.
tools	Build extra tools.

molecule

plugins	Add plugins provided by dev-util/molecule-plugins

nemiver

memoryview	Enable the optional hexadecimal memory inspection with app-editors/ghex.

nvidia-cuda-sdk

cuda	Build CUDA binaries.
opencl	Build OpenCL binaries.

nvidia-cuda-toolkit

debugger	Installs the CUDA debugger.
eclipse	Install plugins for eclipse
profiler	Installs the NVIDIA CUDA visual profiler.

perf

demangle	Enable C++ symbol name demangling, using libbfd from sys-devel/binutils. When this flag is enabled, the package will have to be rebuilt after every version bump of binutils.
doc	Build documentation and man pages. With this USE flag disabled, the --help parameter for perf and its sub-tools will not be available. This is optional because it depends on a few documentation handling tools that are not always welcome on user systems.
numa	Enable NUMA support
perl	Add support for Perl as a scripting language for perf tools.
unwind	Use sys-libs/libunwind for frame unwinding support.

pkgconf

pkg-config	Install as a replacement for dev-util/pkgconfig
strict	Adhere to POSIX pkg-config specification. Useful for finding uses of non-standard pkg-config invocations

pkgconfig

internal-glib	Use internal copy of dev-libs/glib

pkgconfig-openbsd

pkg-config	Install as a replacement for dev-util/pkgconfig

scanmem

gui	Enable the GameConqueror GUI

schroot

btrfs	Enable support for chroots using btrfs snapshots.
dchroot	Enables the building of a wrapper named "dchroot", replacing sys-apps/dchroot.
lvm	Enable support for chroots using LVM snapshots.

squashdelta

lz4	Enable support for LZ4 compression using app-arch/lz4

squashmerge

lz4	Enable support for LZ4 compression using app-arch/lz4

strace

aio	Enable dev-libs/libaio support for tracing Asynchronous I/O operations
unwind	Enable stack backtraces (-k flag) via sys-libs/libunwind

suse-build

symlink	Provide compatibility symlinks with original openSUSE package (might clash with other packages)

sysdig

modules	Build kernel modules needed for tracing local events. Disable this only if you intend to use sysdig purely to work with dumpfiles.

sysprof

systemd	Build the sysprofd daemon service, required to run the UI without root permissions. Relies on sys-apps/systemd running as the init system.

systemtap

libvirt	Support probing of libvirt domains.

trace-cmd

udis86	Enable support for dev-libs/udis86 disassembler library

universalindentgui

html	Add support for HTML files

dev-vcs

bzr

sftp	Enable sftp support

bzr-gtk

gpg	Support signing with GnuPG.
nautilus	Integrate with Nautilus file manager

cssc

valgrind	Enable usage of dev-util/valgrind in tests

cvs

server	Enable server support

cvs2svn

bazaar	Support for dev-vcs/bzr

cvsync

gcrypt	Use dev-libs/libgcrypt for hash functions.
mhash	Use app-crypt/mhash for hash functions.
openssl	Use dev-libs/openssl for hash functions.

darcs

diff	Use 'lcs' for diff building.
http	Use the pure Haskell HTTP package for HTTP support.
network-uri	Get Network.URI from the network-uri package.
terminfo	Use the terminfo package for enhanced console support.
threaded	Use threading and SMP support.

fossil

fusefs	Enable the Fuse Filesystem
json	Enable the JSON API of Fossil's wiki
legacy-mv-rm	Enable legacy behavior for mv/rm (skip checkout files)
miniz	Use the bundled miniz for compression instead of zlib
sqlite	Use the system SQLite instead of the bundled one
th1-docs	Enable TH1 for embedded documentation pages
th1-hooks	Enable TH1 hooks for commands and web pages

git

blksha1	Use the new optimized SHA1 implementation
cgi	Install gitweb too
curl	Support fetching and pushing (requires webdav too) over http:// and https:// protocols
gpg	Pull in gnupg for signing -- without gnupg, attempts at signing will fail at runtime!
highlight	GitWeb support for app-text/highlight
mediawiki	Support pulling and pushing from MediaWiki
mediawiki-experimental	Add experimental patches for improved MediaWiki support
ppcsha1	Make use of a bundled routine that is optimized for the PPC arch
subversion	Include git-svn for dev-vcs/subversion support
tk	Include the 'gitk' and 'git gui' tools
webdav	Adds support for push'ing to HTTP/HTTPS repositories via DAV

git-annex

assistant	Enable git-annex assistant and watch command
benchmark	Enable benchmarking
concurrentoutput	Use concurrent-output library (experimental)
cryptonite	Use the cryptonite library, instead of the older cryptohash
ekg	Enable use of EKG to monitor git-annex as it runs.
magicmime	Use libmagic to determine file MIME types
network-uri	Get Network.URI from the network-uri package.
pairing	Enable pairing of git annex repositories
s3	Enable Amazon S3 remote
torrentparser	Use haskell torrent library to parse torrent files
webapp	Enable git-annex webapp
webdav	Enable webdav remote

gitg

glade	Install a glade catalog file
python	Install Python bindings for those plugins requiring it.

gitolite

contrib	Install user-contributed files
tools	Install tools to e.g. convert a Gitosis config to gitolite or one to check if your setup is gitolite >= 3.x compatible

gitolite-gentoo

contrib	Install user-contributed files
tools	Install tools to e.g. convert a Gitosis config to gitolite or one to check if your setup is gitolite >= 3.x compatible

kdesvn

man	Build and install man pages

mercurial

bugzilla	Support bugzilla integration.
gpg	Support signing with GnuPG.
tk	Install dev-lang/tk for hgk script.

qct

bazaar	Support for dev-vcs/bzr
mercurial	Support for dev-vcs/mercurial
monotone	Support for dev-vcs/monotone

rabbitvcs

caja	Enable extension for mate-base/caja
cli	Eanble console based frontend
diff	Use for diff command dev-util/meld
gedit	Enable plugin for app-editors/gedit
nautilus	Enable extension for gnome-base/nautilus
thunar	Enable extension for xfce-base/thunar

subversion

ctypes-python	Build and install Ctypes Python bindings
dso	Enable runtime module search
extras	Install extra scripts (examples, tools, hooks)
http	Enable http support using net-libs/serf
kwallet	Enable encrypted storage of passwords with kde-apps/kwalletd

games-action

beathazardultra

bundled-libs	Use the upstream provided bundled libraries.

chromium-bsu

mixer	Enables media-libs/sdl-mixer sound backend instead of media-libs/openal one.

d1x-rebirth

demo	Use the demo data instead of the full game
l10n_de	Provides German translations for the game's briefings, robot descriptions, and outro of the original campaign
music	Support for ingame music
opl3-musicpack	Include alternate version of the game's music, recorded with the Yamaha YMF262 OPL3 soundchip
sc55-musicpack	Include alternate version of the game's music, recorded with the Roland Sound Canvas SC-55 MIDI module

d2x-rebirth

demo	Install games-action/descent2-demodata as well
l10n_de	Provides German translations for the game's briefings, robot descriptions, and outro of the original campaign
music	Support for ingame music
opl3-musicpack	Include alternate version of the game's music, recorded with the Yamaha YMF262 OPL3 soundchip
sc55-musicpack	Include alternate version of the game's music, recorded with the Roland Sound Canvas SC-55 MIDI module

dxx-rebirth

data	Install data files
descent1	Install Descent 1 resources and executable
descent2	Install Descent 2 resources and executable
l10n_de	Provides German translations for the game's briefings, robot descriptions, and outro of the original campaign
music	Enable music support
opl3-musicpack	Include alternate version of the game's music, recorded with the Yamaha YMF262 OPL3 soundchip
sc55-musicpack	Include alternate version of the game's music, recorded with the Roland Sound Canvas SC-55 MIDI module
textures	Include high resolution (640x480) backgrounds, briefing images and fonts (Descent 1)

hotline-miami

bundled-libs	Use bundled libraries.
launcher	Install qt launcher

minetest

leveldb	Enable LevelDB backend
luajit	Use dev-lang/luajit instead of dev-lang/lua
redis	Enable redis backend via dev-libs/hiredis
server	Build minetest server
spatial	Enable SpatialIndex AreaStore backend

solar2

bundled-libs	Use the upstream provided bundled libraries.

super-hexagon

bundled-libs	Use the upstream provided bundled libraries.

supertuxkart

fribidi	Support for right-to-left languages
wiimote	Support for wiimote input devices

swordandsworcery

bundled-libs	Use the upstream provided bundled libraries.

trine2

bundled-libs	Use bundled libraries.
launcher	Install gtk+ launcher

games-arcade

bomns

editor	enables building the level editor

burgerspace

network	Enable client-server support

commandergenius

tremor	Use media-libs/tremor as ogg decoder instead of media-libs/libvorbis

jumpnbump

music	Enable playing of background music

lbreakout2

themes	Install additional themes

moleinvasion

music	Download and install the music files

performous

midi	Enable MIDI I/O support
songs	Install a few demo songs
tools	Install tools
webcam	Enable Webcam support

savagewheels

fmod	Enable the fmod music and sound effects library

slimevolley

net	Enable network support

smc

music	Download and install the music files

tuxanci

physfs	Use dev-games/physfs instead of dev-libs/libzip to load compressed data
sound	Enable sound

games-board

cockatrice

server	Compile server support

crafty

no-opts	Don't try to enable crazy CFLAG options

freedoko

backgrounds	Install additional background images
gnomecards	Install the gnome-games card set
kdecards	Install the KDE card set
net	Enable network game support
openclipartcards	Install the openclipartcards card set
pysolcards	Install the PySol card set
xskatcards	Install the XSkat card set

grhino

gtp	Install the GTP (Go/Game Text Protocol) frontend

pasang-emas

extras	Install some extra themes

pioneers

help	Enable gnome ingame help via scrollkeeper

pysolfc

extra-cardsets	Install extra cardsets
sound	Enable sound support using dev-python/pygame

spider

athena	Enable athena widgets

stockfish

armv7	Build for armv7; enables PIE
general-32	Generic unoptimized 32-bits build
general-64	Generic unoptimized 64-bits build
optimize	Enable upstream -O3 optimizations (default enabled)

tablebase-syzygy

6-pieces	Install tablebases for 6 pieces (huge!)

xboard

default-font	Install the default font that xboard uses
zippy	Enable experimental zippy client

games-emulation

dolphin

egl	Enable EGL support
evdev	Enable evdev input support
llvm	Enable the LLVM-based disassembler for debugger mode
log	Increase logging output
lto	Add support for link-time optimizations.

dosbox

glide	Enable unofficial Glide emulation via media-libs/openglide

fceux

logo	Enable the ability to add a logo screen when creating AVIs

generator

sdlaudio	Enable SDL Audio

higan

icarus	Build icarus library manager
profile_accuracy	Compile a binary optimized for accuracy
profile_balanced	Compile a binary with balanced optimization
profile_performance	Compile a binary optimized for performance
udev	Enable udev based input

mednafen

debugger	Build with internal debugger
pax_kernel	Triggers a paxmarking of the binary

mupen64plus

audio-sdl	Enable SDL audio plugin.
input-sdl	Enable SDL input plugin.
rsp-hle	Enable HLE RSP plugin.
ui-console	Enable default console UI.
ui-m64py	Enable PyQt4 UI using games-emulation/m64py.
video-glide64mk2	Enable Glide64mk2 video plugin.
video-rice	Enable Rice video plugin.

mupen64plus-core

debugger	Build the debugger
gles2	Use GLES2 instead of OpenGL
new-dynarec	Enable new experimental dynamic recompiler implementation (only for x86 and arm)
osd	Overlay emulator messages using on-screen-display

mupen64plus-video-glide64mk2

gles2	Use GLES2 instead of OpenGL
hires	Support hi-resolution textures (requires dev-libs/boost)

mupen64plus-video-rice

gles2	Use GLES2 instead of OpenGL

nestopia

gui	Enable GUI

pcsxr

cdio	Use libcdio for CD support
sdl	Use SDL sound backend (other parts of SDL are used unconditionally)

ppsspp

headless	Build headless version of the PPSSPP
system-ffmpeg	Use the system-wide media-video/ffmpeg instead of bundled

sdlmame

arcade	Enable the Multiple Arcade Machine Emulator for arcade games support
mess	Enable the Multi Emulator Super System for game system support
tools	Build development tools shared between sdlmame and sdlmess

snes9x

netplay	Enable playing ROMs over the network (not recommended)
xrandr	Enable support for the X xrandr extension

vbam

link	Enable GBA linking functionality

yabause

pic	disable optimized assembly code that is not PIC friendly

zsnes

debug	Enable the builtin debugger
pax_kernel	Triggers a paxmarking of the binary

games-engines

frobtads

tads2compiler	Build TADS2 compiler
tads3compiler	Build TADS3 compiler

odamex

master	Build master server target (advertises odamex server list)
odalaunch	Build the wxwidgets based launcher.
portmidi	Enable portmidi support.
server	Build server target.

openmw

devtools	Install development tools like bsatool, esmtool and opencs.

renpy

development	Install IDE for game developers and an empty game template

scummvm

fluidsynth	compile with support for fluidsynth
mpeg2	enable mpeg2 codec for cutscenes
unsupported	enable unsupported and/or broken game engines (you're on your own)

solarus

doc	Install doxygen developer documentation.
luajit	Use LuaJIT instead of default Lua.

stratagus

fluidsynth	compile with support for fluidsynth

games-fps

alienarena

vidmode	Link against x11-libs/libXxf86vm. Required for full-screen support.

darkplaces

cdsound	Enables using CD audio in the engine
demo	Uses the demo data from quake1 (quake1-demodata)
lights	Install and setup the updated light maps
textures	Install and setup the updated textures

doom-data

doomsday	Add wrapper to run it within doomsday

doom3

dedicated	install only as a dedicated game server
roe	Adds support for the Resurrection of Evil expansion

doomsday

demo	Install launcher dor doom1.wad from games-fps/doom-data
doom	Install launcher for jdoom game
fluidsynth	Build the FluidSynth sound driver
freedoom	Install launcher for doom1.wad from games-fps/freedoom
heretic	Install launcher for jheretic game
hexen	Install launcher for jhexen game
resources	Enable support for games-fps/doomsday-resources in jdoom launcher
snowberry	Install Snowberry doomsday front-end
tools	Build additional tools such as doomsday-shell, md2tool and texc

duke3d

demo	Install the demo files
pic	disable optimized assembly code that is not PIC friendly

duke3d-data

gog	Extract the data from the GOG.com installer.

eduke32

demo	Install games-fps/duke3d-demodata as well
gtk	Compile with gtk launcher
offensive	Include optional XXX texture pack (needs USE 'textures')
opl-musicpack	Include optional OPL (AdLib) music pack
samples	Install samples
sc55-musicpack	Include optional Roland SC-55 music pack
server	Compile with server support
textures	Include optional high-resolution textures (needs USE 'opengl')
tools	Build several tools for modding and development
vpx	Enable support for WebM VP8 Codecs (needs USE 'opengl')

lsdldoom

freedoom	Install games-fps/freedoom wad file
net	Enables network game support
shareware	Install games-fps/doom-data for shareware wad file

nexuiz

maps	Install the community map pack

quake2-icculus

demo	Install the demo files (quake2-demodata) and configure for use
qmax	Build the pretty version (quake max)
rogue	Build support for the 'Ground Zero' Mission Pack (rogue)
xatrix	Build support for the 'The Reckoning' Mission Pack (xatrix)

quake3

mumble	Adds player-location (positional audio) support to VoIP
teamarena	Adds support for Team Arena expansion pack
voice	Adds VoIP support

quake3-bin

teamarena	Adds support for Team Arena expansion pack

quake3-demo

dedicated	install only as a dedicated game serer

quakeforge

wildmidi	enable libWildMidi support
xdg	enable XDG support

qudos

demo	Install the demo files (quake2-demodata) and configure for use
mods	Build support for the quake2 mission packs
qmax	Build the pretty version (quake max)
textures	Install the enhanced textures (quake2-textures)

rott

demo	Install the shareware version

sauerbraten

server	Compile server support

turtlearena

mumble	Adds player-location (positional audio) support to VoIP
server	Build server target
voice	Adds VoIP support

unreal-tournament-goty

S3TC	Add the extra fancy textures to UT ... only works on certain cards (nvidia/ati/s3)

urbanterror

altgamma	Alternative way for gamma setting with modesetting driver
client	Build binary for client (includes code for non-dedicated server)
mumble	Use Mumble for ingame VoIP (experimental)
opus	Use opus as sound codec
server	Build binary for dedicated server
voip	Use ioq3 ingame VoIP (experimental)

warsow

irc	Enable IRC support
server	Build server binaries additionally

worldofpadman

maps	Install extra maps (PadPack)

xonotic

ode	Enable support for physics engine from dev-games/ode

games-kids

crayon-physics

bundled-libs	Use the upstream provided bundled libraries.

games-misc

katawa-shoujo

system-renpy	Use games-engines/renpy instead of the bundled one (experimental)

little-inferno

bundled-libs	Use bundled libraries.

ponysay

fish-completion	Enable fish completion support
non-free	Install non-free ponies (i.e. from the MLP franchise)

xcowsay

fortune	Installs the fortune-mod xcow binary

games-mud

tf

atcp	enable ATCP support.
gmcp	enable GMCP support.
option102	enable telnet option 102 support.

games-puzzle

cuyo

music	Enable playing of background music

jag

editor	Install level editor

nightsky

bundled-libs	Use the upstream provided bundled libraries.

numptyphysics

user-levels	Install some fun user-created levels

pingus

music	Enable playing of background music

sgt-puzzles

gtk3	Use x11-libs/gtk+:3 instead of x11-libs/gtk+:2

tiny-and-big

bundled-libs	Use the upstream provided bundled libraries.

xlogical

alt_gfx	Use alternate graphics which are closer to the original Amiga version

games-roguelike

FTL

bundled-libs	Use bundled libraries.

angband

sound	Enable and install sounds

nethack

experimental	Enable experimental features (showscore and status_hilite)

stone-soup

luajit	Use dev-lang/luajit as scripting backend instead of dev-lang/lua.
ncurses	Enable for console (uses ncurses) based build. (can be enabled on top of tiles)
tiles	Enable for graphical (tiled) build. (can be enabled on top of ncurses)

tomenet

server	Compile server support

games-rpg

a-bird-story

bundled-libs	Use bundled libraries

arx-fatalis-data

gog	Extract the data from the GOG.com installer.

arx-libertatis

c++0x	Build ROOT using the C++11 standard.
crash-reporter	Build a dev-qt/qtgui-based tool that allows to submit crash information to the upstream backtracker.
debug	Enable asserts and debug logging.
static	Link libraries statically, currently only media-libs/glew
tools	Build tools that can extract the game's data and save files.
unity-build	Build everything in one big source file, allowing for faster build times and better optimizations at the cost of higher memory usage.

daimonin-client

music	Install extra music

drascula

sound	Install optional audio files

dreamweb

doc	High-resolution scans of the written material in the original UK game box

dungeon-defenders

bundled-libs	Use the upstream provided bundled libraries.

eternal-lands-data

bloodsuckermaps	Will install Bloodsucker's Maps in place of the official map files.
music	Adds in-game music.
sound	Adds in-game sound effects.

grimrock

bundled-libs	Use bundled libraries.

kqlives

cheats	Enable cheating mode

manaplus

mumble	Enable support for voice chat
pugixml	Use dev-libs/pugixml for XML parsing isntead of dev-libs/libxml2
sdl2	Use libsdl2 instead of libsdl

nwn

hou	Install the Hordes of the Underdark expansion pack
sou	Installs the Shadows of Undrentide expension pack

nwn-data

hou	Install the Hordes of the Underdark expansion pack
nowin	For those people who cant grab the 1.2 gigs of data files from a windows partition
sou	Installs the Shadows of Undrentide expension pack

sumwars

tools	Builds editor tools

to-the-moon

bundled-libs	Use bundled libraries

games-simulation

flightgear

dbus	Enable screensaver DBus interaction
gdal	Enable alternative terrain engine based on pagedLOD using sci-libs/gdal
qt5	Build Qt5 launcher application
udev	Enable event-based Input devices through virtual/udev
utils	Build various utilities (fgpanel, fgviewer among others)

openttd

aplaymidi	Enables midi music in game, using aplaymidi as an external player
dedicated	Build only the openttd server, and not the client.
lzo	Enables LZO compression for savegames. This is only needed to load extremely old savegames. (versions before 0.2)
openmedia	Enables the free open media sets: OpenGFX, OpenSFX, OpenMSX, removing the requirement for proprietary TTD assets to play OpenTTD.

singularity

music	Install music files

games-sports

speed-dreams

xrandr	Enable support for the X xrandr extension

xmoto

editor	Depend on inkscape, scripts to convert svg to level (svg2lvl)

games-strategy

0ad

editor	Include Atlas scenario editor projects
lobby	Enable the use of net-libs/gloox and the multiplayer lobby
nvtt	Support for some uncompressed data formats via media-gfx/nvidia-texture-tools (might be needed for some mods)

defcon-demo

system-libs	Use system libraries instead of the ones included in the upstream distribution.

freeciv

aimodules	Support for dynamically loadable AI modules (server-side)
auth	Add authentication capability via mysql, postgres or sqlite3
mapimg	Additional mag image toolkit via media-gfx/imagemagick
modpack	Build the freeciv-modpack-program to download/install mods
server	Enable server support. Disabling this will also make it impossible to start local games.
sound	Add support for sound provided by media-libs/sdl-mixer
system-lua	Use dev-lang/lua instead of the bundled liblua

freesynd

devtools	Build development tools

heroes3

maps	Installs optional map data
music	Installs optional music data
sounds	Installs optional sound data

ja2-stracciatella

editor	Adds necessary file to run the editor
linguas_ru_gold	Support for russian gold ja2 version

liquidwar6

doc	Convert the info pages to html
gles2	Enable OpenGL ES 2.0 support
gtk	Used to display error/critical messages
maps	Install extra maps
ogg	Enable mod-ogg via media-libs/sdl-mixer (currently the only sound provider)
readline	Enable interactive script shell for hacking

megaglest

editor	Build map editor
fribidi	Enable FriBIDi support
model-viewer	Build model viewer
streflop	Use the library streflop. Out of synchs may occur if not enabled.
tools	Build model import/export tools
unicode	Use unicode strings for wxwidgets
wxuniversal	Use the wxUniversal port which implements the various GUI controls by drawing them itself

naev

mixer	Enables media-libs/sdl-mixer sound backend in addition to media-libs/openal one.

openra

tools	Install some development tools such as editor.

seven-kingdoms

network	Enable support for multiplayer via media-libs/sdl-net

ufo-ai

editor	Build map editor

uqm

music	download and install music files (large)
remix	download and install music remix files (large)
voice	download and install voice files (large)

warzone2100

qt4	Use qt-gui/qt-opengl for backend rendering instead of sdl

wesnoth

fribidi	Support for right-to-left languages
server	Enable compilation of server

games-util

gslist

web	Enable the web interface

pyfa

graph	Enable support for graphs

wit

fuse	Enable image mount support via fuse

gnome-base

gconf

ldap	Build backend which enables default mail accounts, addressbooks and calendars for Evolution to be configured using each user's LDAP entry."

gdm

fprint	Enables experimental fingerprint authentication using sys-auth/fprintd
plymouth	Enable support for smooth transition from sys-boot/plymouth

gnome

classic	Install gnome-extra/gnome-shell-extensions for the Gnome Shell Classic mode
extras	Install additional GNOME applications

gnome-common

autoconf-archive	Pull in sys-devel/autoconf-archive for ax_*.m4 files instead of installing them from the gnome-common tarball

gnome-control-center

colord	Support color management using x11-misc/colord
gnome-online-accounts	Enable configuration panel for net-libs/gnome-online-accounts accounts
ibus	Enable support for enhanced input methods through app-i18n/ibus

gnome-desktop

license-docs	Install help files documenting GNOME's licenses

gnome-extra-apps

games	Install Gnome Games
share	Install the gnome-extra/gnome-user-share personal file sharing tool
shotwell	Install the media-gfx/shotwell photo manager
tracker	Install the app-misc/tracker indexer and the GNOME packages that require it

gnome-keyring

ssh-agent	Use GNOME Keyring to unlock SSH keys. Recommended unless you are using ECDSA or Ed25519 keys.

gnome-light

gnome-shell	Install gnome-base/gnome-shell and x11-wm/mutter for the standard GNOME 3 desktop mode

gnome-settings-daemon

colord	Support color management using x11-misc/colord
openrc-force	Skip systemd dependency (#480336), enabling this flag will become your setup to be fully unsupported by upstream and downstream Gnome team. Do not try to enable it unless completely needed

gnome-shell

browser-extension	Ensure the presence of extensions.gnome.org native connector gnome-extra/chrome-gnome-shell
ibus	Enable support for enhanced input methods through app-i18n/ibus
openrc-force	Skip systemd dependency (#480336), enabling this flag will become your setup to be fully unsupported by upstream and downstream Gnome team. Do not try to enable it unless completely needed

gvfs

afp	Enables support for accessing AFP (Apple Filing Protocol) network shares
archive	Enables support for accessing files in archives transparently via app-arch/libarchive
bluray	Enable playback of Blu-ray filesystems using media-libs/libbluray
fuse	Enables fuse mount points in $HOME/.gvfs for legacy application access
gnome-online-accounts	Enable configuration panel for net-libs/gnome-online-accounts accounts
google	Enables support for accessing Google accounts via dev-libs/libgdata
http	Enable the HTTP/DAV backend using net-libs/libsoup
nfs	Enable NFS client support via net-fs/libnfs.
udev	Enable udev base replacement code for cdda feature

libglade

tools	Install libglade-convert Python script.

libgnomecanvas

glade	Enable glade support

librsvg

tools	Build svg viewer tool

nautilus

packagekit	Use packagekit to search for programs to open unknown file types
previewer	Use gnome-extra/sushi to preview files from the file mananger
sendto	Enable the nautilus-sendto extension to send files to various locations/devices
tracker	Add support for app-misc/tracker search

orbit

pic	Force libname-server-2 to be built as PIC; needed on hardened systems

gnome-extra

cinnamon-control-center

colord	Support color management using x11-misc/colord

cinnamon-settings-daemon

colord	Support color management using x11-misc/colord

evolution-data-server

api-doc-extras	Build documentation for private APIs
berkdb	sys-libs/db support needed to migrate old (pre-3.12 evolution versions) addressbook data
gnome-online-accounts	Enable net-libs/gnome-online-accounts based Google authentication support
google	Enable internal Google authentication support. If gnome-online-accounts is enabled and used, this is not necessary, but both can be supported at the same time with different setup at runtime
weather	Enable optional weather calendar support

gnome-builder

clang	Provide integration with sys-devel/clang for best possible C/C++ autocompletion, semantic highlighting, symbol resolving, and diagnostics support
git	Provide support for the Git version control system via dev-libs/libgit2-glib (such as setup of Git for New Project, direct cloning for Open Project and changed lines indicators in the editor gutter)
sysprof	Provide an integrated profiler via dev-util/sysprof
vala	Provide an autoindenter, autocompletion, diagnostics, and symbol resolver for Vala
webkit	Enable net-libs/webkit-gtk using plugins support and the HTML/Markdown previewer plugin

gnome-color-manager

packagekit	Enable support for the distro-neutral package manager GUI app-admin/packagekit

gnome-commander

chm	Enable metadata support for Microsoft Compiled HTML Help files
gsf	Add metadata support for OLE, OLE2 and ODF
pdf	Add metadata support for PDF
python	Add support for python plugins
samba	Add support for SAMBA (Windows File and Printer sharing)
taglib	Add metadata support for ID3, Vorbis, FLAC and APE
unique	Enable single instance support using dev-libs/libunique

gnome-dvb-daemon

totem	Build a plugin for media-video/totem

gnome-system-monitor

systemd	Display sys-apps/systemd metadata, e.g. unit names, for running processes

libgda

canvas	Enable support for x11-libs/goocanvas
http	Enable embedded net-libs/libsoup based server
json	Enable support for JSON format
mdb	Enable support for Microsoft Access database using app-office/mdbtools
reports	Install tools for generating graphical reports
sourceview	Enable support for x11-libs/gtksourceview

libgsf

gtk	Enable use of gdk in thumbnailer

nemo

packagekit	Use packagekit to search for programs to open unknown file types
tracker	Add support for app-misc/tracker search

nm-applet

gcr	Enable advanced certificate chooser, requires app-crypt/gcr
modemmanager	Enable support for mobile broadband devices using net-misc/modemmanager
teamd	Enable teamd configuration editor

sushi

office	Support viewing file formats such as generated by app-office/libreoffice

synapse

plugins	Build support for plugins using librest
zeitgeist	Add support for Zeitgeist event tracking system

zeitgeist

datahub	Use build datahub for passive event injection
downloads-monitor	Monitor the XDG_DOWNLOAD_DIRECTORY
fts	Enable the full text search extension
sql-debug	Enable SQL debugging
telepathy	Enable telepathy framework as data source

gnustep-apps

gemas

projectcenter	Build and install plugin for gnustep-apps/projectcenter

gnumail

emoticon	Enable extra Emoticon Bundle to see smiley's in e-mail messages

gworkspace

gwmetadata	Enable the metadata indexing and searching system

gnustep-base

gnustep-back-art

xim	Enable X11 XiM input method

gnustep-back-cairo

xim	Enable X11 XiM input method

gnustep-back-xlib

xim	Enable X11 XiM input method

gnustep-gui

speech	Audio support using app-accessibility/flite

gnustep-make

libobjc2	Enables use of the GNUstep Objective-C runtime (gnustep-base/libobjc2) with non-fragile ABI and sys-devel/clang compiler
native-exceptions	Enables use of the native Objective-C exception support (@try/@catch/@finally) built-in objective-c exceptions with compilers that support it

libobjc2

boehm-gc	Enable Hans Boehm's garbage collector (dev-libs/boehm-gc). Not recommended by upstream

kde-apps

akonadi

designer	Install plugin for dev-qt/designer
tools	Install tools for developers and testing

akonadi-contacts

prison	Enable support for QRcodes in contacts

analitza

eigen	Enable dev-cpp/eigen mathematical templates support

ark

zip	Enable ZIP archive support via dev-libs/libzip

artikulate

qtmedia	Enable playback via Qt5Multimedia

blogilo

google	Google service integration via kde-apps/libkgapi

cantor

R	Enable dev-lang/R backend support
analitza	Enable kde-apps/analitza backend support
julia	Enable dev-lang/julia backend support
qalculate	Enable sci-libs/libqalculate backend support

dolphin

thumbnail	Enables video thumbnail generation

dolphin-plugins

bazaar	Enable support for the bazaar VCS
dropbox	Enable support for the dropbox fileviewer plugin
git	Enable support for the git VCS
mercurial	Enable support for the mercurial VCS

gwenview

kipi	Support for the KDE Image Plugin Interface

k3b

emovix	Enable burning support for eMoviX images

kaccessible

speechd	Enable support for the speech-dispatcher speech synthesizer

kaddressbook

prison	Enable support for QRcodes in contacts

kalzium

editor	Enable the embedded molecule editor/viewer
solver	Enable the equation solver

kate

addons	Build and install additional plugins

kde-apps-meta

pim	Pull in KDE PIM suite
sdk	Pull in developer-specific meta-packages

kdeadmin-meta

cron	Installs KDE application for virtual/cron configuration

kdebase-kioslaves

sftp	Enable SFTP protocol support using net-libs/libssh

kdebase-runtime-meta

kwallet	Enable encrypted storage of passwords with kde-frameworks/kwallet

kdegraphics-mobipocket

thumbnail	Enables thumbnail generation

kdemultimedia-meta

cdrom	Include packages for optical discs

kdenetwork-meta

ppp	Enable support for net-dialup/ppp.

kdenlive

freesound	Enable freesound.org credentials support via dev-qt/qtwebkit to download files
gles2	Use GLES 2.0 or later instead of full OpenGL
jogshuttle	Enable support for Jog-Shuttle devices

kdepim-apps-libs

prison	Enable support for QRcodes in contacts

kdepim-common-libs

google	Google service integration via kde-apps/libkgapi

kdepim-meta

google	Google service integration via kde-apps/libkgapi

kdepim-runtime

google	Google service integration via kde-apps/libkgapi

kdepimlibs

prison	Enable support for QRcodes in contacts

kdeutils-meta

floppy	Install kde-apps/kfloppy to format and create DOS or ext2fs filesystems in a floppy.

keditbookmarks

man	Build and install man pages

kget

bittorrent	Enable bittorrent transfer plugin through net-libs/libktorrent
mms	Enable MMS (Microsoft Media Server) plugin through media-libs/libmms

kig

geogebra	Support files created by sci-mathematics/geogebra
scripting	Support Python scripting

kio-extras

activities	Enable activities kioslave and fileitem plugin
htmlthumbs	Enable HTML thumbnail previews via dev-qt/qtwebengine
man	Enable manpages kioslave
phonon	Enable file audio preview plugin using media-libs/phonon
sftp	Enable SFTP protocol support using net-libs/libssh

konqueror

activities	Enable kactivities support
speech	Build text-to-speech plugin

kopete

addbookmarks	Automatically add incoming urls to bookmarks.
autoreplace	Automatically replace selected text
contactnotes	Enables writing personal notes for contacts.
cryptography	Enable cryptography plugin
gadu	Enable the Gadu protocol handler.
groupwise	Enable the Groupwise protocol handler.
highlight	Allows you to specify highlights on specific events.
history	Enables saving chat history.
latex	Embed latex formatted text into messages.
meanwhile	Enable the Sametime protocol handler.
nowlistening	Shows song you currently listen to in your status/etc. Bindings for many players.
otr	Allows crypting your chat (drugs and talking nonsense are considered as good alternatives ;]).
pipes	Send messages to external pipe.
privacy	Filter for incoming messages
skype	Enable Skype protocol handler (not fully functional yet).
statistics	Everybody loves statistic graphs, especially cake ones. ;]
testbed	Enable the testbed protocol.
texteffect	Various fancy text effects for your messages (don't ever consider writing us with this enabled ;]).
translator	Translate incoming and outgoing messages.
urlpicpreview	Enables in conversation pictures preview.
webpresence	Show your status and some more information on web.
winpopup	Enable pop-up messages sending on windows. (same as good old "net send" messages ;])
yahoo	Enable yahoo protocol support.
zeroconf	Enable Link-Local Messaging via the bonjour protocol.

kpimtextedit

designer	Build plugins for dev-qt/designer
speech	Enable text-to-speech support

krfb

ktp	Enable displaying of KDE Telepathy contacts
telepathy	Enable desktop sharing through a telepathy client

kstars

fits	Enable support for NASA's sci-libs/cfitsio library
indi	Enable support for Astronomical control library using libindi
wcs	Enable support for World Coordinate System library using wcslib
xplanet	Enable support for Xplanet

ktp-accounts-kcm

experimental	Enables disabled telepathy services (currently only steam)

ktp-common-internals

otr	Enable support for encrypted conversations using Off-The-Records messaging
sso	Enable support for Single sign-on through KAccounts

ktp-text-ui

speech	Enable incoming messages to be read out using text-to-speech

kwalletd

gpg	Support wallets with GnuPG encryption additionally to default blowfish-encrypted file

kwave

opus	Enable Opus audio codec support
qtmedia	Enable playback via Qt5Multimedia

libkdepim

designer	Build plugins for dev-qt/designer

mailcommon

designer	Build plugins for dev-qt/designer

marble

aprs	Enable support for APRS data sources
designer	Install plugin for dev-qt/designer
phonon	Enable sound support via media-libs/phonon
positioning	Enable position information via dev-qt/qtpositioning and dev-qt/qtlocation
shapefile	Enable support for ESRI shapefiles

okteta

designer	Build plugins for dev-qt/designer

okular

chm	Enable support for Microsoft Compiled HTML Help files
ebook	Add E-Book support
image-backend	Enable image viewing support
mobi	Add mobipocket support
mobile	Enable Plasma mobile support
plucker	Enable Plucker E-Book for Palm OS devices support
speech	Enable text-to-speech support

pimcommon

designer	Build plugins for dev-qt/designer

spectacle

kipi	Enable support for the KDE Image Plugin Interface
share	Enable support for a share menu using dev-libs/purpose

step

qalculate	Enable the libqalculate library for unit conversion

kde-frameworks

frameworkintegration

appstream	Enable AppStream software metadata support

kconfigwidgets

man	Build and install man pages

kded

man	Build and install man pages

kdelibs

opengl	Enable OpenGL support for Plasma (GLApplet)

kdesignerplugin

designer	Build KF5 widgets plugin for QtDesigner
webkit	Build kdewebkit plugin for QtDesigner

kfilemetadata

epub	Enable support for reading EPUB ebook metadata
office	Enable support for reading ODF and OOXML metadata

kimageformats

eps	Support the EPS graphics file format

kinit

caps	Capabilities support for improved security and better OOM handling
man	Build and install man pages

kio

kwallet	Enable permanent storage of passwords for kpasswdserver with kde-frameworks/kwallet

knotifications

speech	Enable text-to-speech notification support

knotifyconfig

phonon	Add sound support via media-libs/phonon

kpackage

man	Build and install man pages

kservice

man	Build and install man pages

ktexteditor

editorconfig	Enable support for EditorConfig configuration files

ktextwidgets

speech	Enable text-to-speech support

kwallet

gpg	Support wallets with GnuPG encryption in addition to the default blowfish-encrypted file
man	Build and install man pages

kxmlgui

attica	Enable support for kde-frameworks/attica

networkmanager-qt

teamd	Enable Teamd control support

oxygen-icons

sources	Additionally install the svg sources of the bitmap icons (needed for redistribution)

plasma

gles2	Use GLES 2.0 or later instead of full OpenGL

sonnet

aspell	Enable the app-text/aspell spell-checking backend
hunspell	Enable the app-text/hunspell spell-checking backend

kde-misc

kdeconnect

app	Enable experimental kcapp frontend
wayland	Enable kwin_wayland support for mousepad plugin using kde-frameworks/kwayland

kimtoy

scim	Enable Smart Common Input Method support

kio-gdrive

kaccounts	Use kde-apps/kaccounts-integration backend (default) instead of dev-libs/qtkeychain

tellico

discid	Add support for reading disc IDs from audio CDs

kde-plasma

kde-cli-tools

kdesu	Build graphical frontend for kde-frameworks/kdesu

kde-gtk-config

gtk3	Add support for gtk+3-based applications.

kdeplasma-addons

share	Enable applet for quickly sharing data to a variety of sources

kinfocenter

egl	Retrieve information about OpenGL via EGL
gles2	Show OpenGL ES information in kinfocenter
pci	Show advanced PCI information

kmenuedit

hotkeys	Enable support for hotkey editing

kwallet-pam

oldwallet	Enable legacy support for kde-apps/kwalletd

kwin

gles2	Use OpenGL ES 2 instead of full GL
multimedia	Enable effect video button in desktop effects KCM

libksysguard

detailedmemory	Enable display of detailed memory information using dev-qt/qtwebkit.

plasma-desktop

appstream	Enable AppStream software metadata support
gtk2	Add support for gtk+2-based applications using legacy xembed systray icons via libappindicator.
gtk3	Add support for gtk+3-based applications using legacy xembed systray icons via libappindicator.
ibus	Use ibus input method via app-i18n/ibus
legacy-systray	Add support for applications using legacy xembed systray icons.
packagekit	Add support for packagekit integration
scim	Enable applets that use app-i18n/scim

plasma-meta

display-manager	Pull in a graphical display manager
grub	Pull in Breeze theme for sys-boot/grub
gtk	Enable Breeze widget style and KCM for GTK2 and GTK3
pam	Enable support for kwallet auto-unlocking
plymouth	Pull in Breeze theme for sys-boot/plymouth
pulseaudio	Install Plasma applet for PulseAudio volume management
sddm	Pull in the x11-misc/sddm display manager and KCM
sdk	Pull in kde-plasma/plasma-sdk for Plasma development
wallpapers	Install wallpapers for the Plasma Workspace

plasma-nm

modemmanager	Enable support for mobile broadband devices
openconnect	Build support for the OpenConnect VPN client
teamd	Enable Teamd control support

plasma-sdk

plasmate	IDE for writing Plasma/KWin components (themes, plasmoids, runners, data engines)

plasma-workspace

geolocation	Enables dataengine providing location information
prison	Enable support for barcodes/QRcodes
qalculate	Enable Qalculate runner using sci-libs/libqalculate

powerdevil

consolekit	Enable sys-auth/consolekit support
elogind	Use sys-auth/elogind for session tracking
wireless	Enable wireless energy saving actions via kde-frameworks/bluez-qt and kde-frameworks/networkmanager-qt

systemsettings

classic	Enable classic mode plugin, requires kde-frameworks/khtml

lxde-base

lxdm

consolekit	Enables support for authorization using consolekit
gtk3	Use GTK+3 instead of 2

lxterminal

gtk3	Use GTK+3 instead of GTK+2

lxqt-base

lxqt-meta

about	Install lxqt-base/lxqt-about
admin	Install lxqt-base/lxqt-admin
filemanager	Install x11-misc/pcmanfm-qt file manager
icons	Install an icon theme
lightdm	Install x11-misc/lightdm display manager
lximage	Install media-gfx/lximage-qt image viewer
minimal	Do not install x11-wm/openbox window manager
oxygen	Prefer kde-frameworks/oxygen-icons (default)
powermanagement	Install lxqt-base/lxqt-powermanagement package
sddm	Install x11-misc/sddm display manager
ssh-askpass	Install lxqt-base/lxqt-openssh-askpass user password prompt tool
sudo	Install lxqt-base/lxqt-sudo

lxqt-panel

clock	Build clock plugin
colorpicker	Build colorpicker plugin
cpuload	Build cpuload plugin
desktopswitch	Build desktopswitch plugin
dom	Build dom plugin
kbindicator	Build kbindicator plugin
mainmenu	Build mainmenu plugin
mount	Build mount plugin
networkmonitor	Build networkmonitor plugin
quicklaunch	Build quicklaunch plugin
screensaver	Build screensaver plugin
sensors	Build sensors plugin
showdesktop	Build showdesktop plugin
statusnotifier	Build statusnotifier plugin
sysstat	Build sysstat plugin
taskbar	Build taskbar plugin
tray	Build tray plugin
volume	Build volume plugin
worldclock	Build worldclock plugin

mail-client

alot

doc	Install user manual and API documentation

alpine

chappa	enhance alpine by applying Eduardo Chappa's patches
onlyalpine	installs only the alpine binary, so it does not collied with pico and/or pine
passfile	Adds support for caching passwords into a file between sessions
smime	Enable support for S/MIME

balsa

crypt	Adds support for GnuPG encryption
gtkhtml	Use gtkhtml for HTML rendering
gtkspell	Use gtkspell for dictionary support
rubrica	Adds support for app-office/rubrica addressbook

claws-mail

archive	Enable archiving plugin
bogofilter	Build mail-filter/bogofilter plugin
gdata	Enable plugin for access to Google data providers
gtk3	Build support for GTK+3
libcanberra	Enable sound notification in connection with USE=notification
libindicate	Enable notification through DBUS in connection with USE=notification
libnotify	Enable notification on the desktop in connection with USE=notification
notification	Notification for new mail in different way, see also USE flags libcanberra, libindicate and libnotify
pgp	Enable PGP support
sieve	Build plugin for sieve filter support
smime	Build plugin for S/MIME support
spam-report	Enable plugin for spam reporting to various services
spamassassin	Build mail-filter/spamassassin plugin
valgrind	Add support for memory debugging using valgrind
webkit	Enables HTML e-mail rendering by using the net-libs/webkit-gtk library.

evolution

archive	Enable archives support in attachments via app-arch/gnome-autoar
bogofilter	Build mail-filter/bogofilter plugin
crypt	Enable GPG encryption support using app-crypt/gnupg and app-crypt/pinentry
geolocation	Enable support for displaying contacts on a map inside evolution using media-libs/libchamplain
highlight	Enable text highlighting plugin
ldap	Enable support for fetching contacts from an LDAP or Active Directory server using net-nds/openldap
spamassassin	Build mail-filter/spamassassin plugin
weather	Enable optional weather calendar support

mail-notification

sylpheed	Enable support for MH mailboxes used by mail-client/sylpheed

mutt

gpg	Enable support for app-crypt/gpgme
hcache	Enable header cache
lmdb	Enable dev-db/lmdb database backend for header caching
notmuch	Enable support for net-mail/notmuch
pop	Enable support for POP3
sidebar	Enable the sidebar feature
smime	Enable support for S/MIME
smtp	Enable support for smtp
tokyocabinet	Enable dev-db/tokyocabinet database backend for header caching

nail

kerberos	If network is enabled, this adds support for GSSAPI login on IMAP through virtual/krb5.
net	Enable support for network protocols (POP, IMAP and SMTP). If you only need to send mail with the local Transport Agent, disabling this will get you support for only /usr/sbin/sendmail call.
ssl	If network is enabled, this adds support for S/MIME and SSL/TLS-powered protocols through dev-libs/openssl.

roundcube

enigma	Add dependencies to support server-side GnuPG signing and/or encryption through the enigma plugin
ldap	Add dependencies to support connecting to an LDAP address book server
managesieve	Add dependencies to support the sieverules plugin

squirrelmail

filter	Enable mail-filter/amavisd-new filtering

sylpheed

oniguruma	Use dev-libs/oniguruma for regular expression

thunderbird

bindist	Disable official Thunderbird branding (icons, name) which are not binary-redistributable according to upstream.
crypt	Enable encryption support with enigmail
custom-optimization	Build with user-specified compiler optimizations (-Os, -O0, -O1, -O2, -O3) from CFLAGS (unsupported)
gtk2	Use the cairo-gtk2 rendering engine instead of the default cairo-gtk3
jemalloc	Enable or disable jemalloc
jemalloc3	Enable or disable jemalloc3 (forced-on when supported prior to 38.0)
lightning	Enable app-global calendar support (note 38.0 and above bundles calendar support when this flag is off)
minimal	Remove the software development kit and headers
mozdom	Enable Mozilla's DOM inspector
rust	Enable support for using rust compiler (experimental)
system-cairo	Use the system-wide x11-libs/cairo instead of bundled.
system-harfbuzz	Use the system-wide media-libs/harfbuzz and media-gfx/graphite2 instead of bundled.
system-icu	Use the system-wide dev-libs/icu instead of bundled.
system-jpeg	Use the system-wide media-libs/libjpeg-turbo instead of bundled.
system-libevent	Use the system-wide dev-libs/libevent instead of bundled.
system-libvpx	Use the system-wide media-libs/libvpx instead of bundled.
system-sqlite	Use the system-wide dev-db/sqlite installation with secure-delete enabled

thunderbird-bin

crashreporter	Enable crash reporter for bugs

trojita

password	Store passwords securely via dev-libs/qtkeychain

mail-filter

MailScanner

exim	Set mail-mta/exim to used MTA
postfix	Set mail-mta/postfix to used MTA
spamassassin	Enable usage of mail-filter/spamassassin for spam protection

amavisd-new

courier	Add courier support
dkim	Add DomainKeys Identified Mail support
qmail	Add qmail support
razor	Add support for mail-filter/razor
spamassassin	Add support for mail-filter/spamassassin
zmq	Add support for zeromq sockets

ask

procmail	Adds support for mail-filter/procmail

assp

spf	Adds support for Sender Policy Framework
srs	Adds support for Sender Rewriting Scheme

bogofilter

tokyocabinet	Enable Tokyo Cabinet database support

clamassassin

clamd	Use the app-antivirus/clamav daemon for virus checking
subject-rewrite	Adds support for subject rewriting

dcc

rrdtool	Enable net-analyzer/rrdtool interface scripts

dspam

daemon	Enable support for DSPAM to run in --daemon mode
debug	Enable debugging support (don't enable this unless something needs testing!)
domain-scale	Build for domain scale setups - puts data to $HOME/data/domain.com/user
hash	Enable support for the file-orientated hash driver
large-scale	Build for large scale setups - puts data to $HOME/data/u/s/user
small-scale	Build for small scale setups - puts data to $HOME/data/user
user-homedirs	Build with user homedir support
virtual-users	Build with virtual-users support

libmilter

poll	Use poll instead of select

maildrop

authlib	Add courier-authlib support
dovecot	Add dovecot authentication support
tools	Install maildirmake and deliverquota tools
trashquota	Count deleted messages as part of the maildir quota

mimedefang

poll	Use poll instead of select

opendkim

ldap	Enable openldap as a dataset facilitator or keys, determining domains to sign for, and any other dataset that opendkim supports.
lmdb	Add support for using dev-db/lmdb
lua	Enables control over signature verification, filtering and policy to be controlled by user defined lua scripts.
memcached	Add support for using dev-libs/libmemcached
opendbx	Use opendbx backend to facilitate dataset driven OpenDKIM configuration options like stats, bodylengthdb, etc. against a wide variety of database types
poll	Use poll() instead of select() for the provided asynchronous resolver library.
sasl	Used to authenticate to a LDAP server in various ways if required.
unbound	Use the unbound dnssec library to perform DKIM DNS queries.

opendmarc

spf	Use the mail-filter/libspf2 for Sender Policy Framework checking

opensmtpd-extras

filter-clamav	filter for scanning with app-antivirus/clamav
filter-dkim-signer	filter for adding DKIM signatures to outgoing messages
filter-dnsbl	filter for checking hosts against the DNS black lists
filter-lua	filter for interfacing with dev-lang/lua
filter-monkey	filter for arbitrarily rejecting random emails
filter-pause	filter to pause on new connections
filter-perl	filter for interfacing with dev-lang/perl
filter-python	filter for interfacing with dev-lang/python
filter-regex	filter for regular expression matching
filter-spamassassin	filter for scanning with mail-filter/spamassassin
filter-stub	stub filter
filter-trace	trace filter
filter-void	void filter
luajit	Use JIT for Lua via dev-lang/luajit instead of dev-lang/lua
queue-null	null queue
queue-python	queue for interfacing with dev-lang/python
queue-ram	ram queue
queue-stub	stub queue
scheduler-python	schedulre for interfacing with python
scheduler-ram	ram scheduler
scheduler-stub	stub scheduler
table-ldap	table for lookups with net-nds/openldap
table-mysql	table for lookups with virtual/mysql
table-passwd	table for lookups using /etc/passwd
table-postgres	table for lookups with dev-db/postgresql
table-python	table for interfacing with dev-lang/python
table-redis	table for lookups with dev-db/redis
table-socketmap	table for lookups using a socket map
table-sqlite	table for lookups with dev-db/sqlite3
table-stub	stub table

postfwd

tools	Install additional tools for testing postfwd

postgrey

targrey	Enables the targrey patch

qmail-scanner

spamassassin	Build faster mail-filter/spamassassin checks into qmail-scanner

rmilter

dkim	Enable support for DomainKeys Identified Mail
memcached	Enable support for memcached

rspamd

fann	Enable neural network plugin (requires sci-mathematics/fann).
jemalloc	Use dev-libs/jemalloc for allocations
pcre2	Use dev-libs/libpcre2

spamassassin

bayes	Require a database (MySQL, SQLite, Postgres, or BerkDB) backend to enable the Bayesian filtering database. If you use the Redis backend, you do not need to enable this flag (Redis support is enabled automatically, and has no external dependencies).
cron	Install a cron job to update SpamAssassin's rules daily.
qmail	Build qmail functionality and docs

spamdyke

ssl	Enables TLS protocol for spamdyke

zdkimfilter

debug	Log process and signal information. Also leave the child process running for gdb examination.
opendbx	An alternate statistics based storage engine.

mail-mta

courier

fax	Enables fax support in the courier mail server
norewrite	Prevents courier mail server from mangling virtual user addresses when sending
web	Enable the web interface
webmail	Enable the webmail interface

exim

dane	Adds support for DNS-based Authentication of Named Entities
dcc	Adds support for Distributed Checksum Clearinghouse (DCC)
dkim	Adds support for DomainKeys Identified Mail (DKIM)
dlfunc	Install local_scan.h header to compile separate dlfunc libraries
dmarc	Adds support for DMARC
dnsdb	Adds support for a DNS search for a record whose domain name is the supplied query
dovecot-sasl	Adds support for Dovecot's authentication
dsn	Adds support for Delivery Status Notifications (DSN)
exiscan-acl	Patch providing support for content scanning
lmtp	Adds support for lmtp
mbx	Adds support for UW's mbx format
pkcs11	Require pkcs11 support in net-libs/gnutls with USE=gnutls
prdr	Adds support for Per-Recipient Data Response
proxy	Add support for being behind a proxy, such as HAProxy
redis	Adds support for querying dev-db/redis
spf	Adds support for Sender Policy Framework
srs	Adds support for Sender Rewriting Scheme
tpda	Adds support for Transport Post-Delivery Actions

msmtp

libsecret	Enable libsecret support to store login credentials
mta	Enable this to install as system-wide MTA

netqmail

authcram	Enable AUTHCRAM support
gencertdaily	Generate SSL certificates daily instead of hourly
highvolume	Prepare netqmail for high volume servers

opensmtpd

mta	Enable this to install as system-wide MTA

postfix

dovecot-sasl	Enable net-mail/dovecot protocol version 1 (server only) SASL implementation
eai	Add support for SMTPUTF8
ldap-bind	Add support for binding to LDAP backend using dev-libs/cyrus-sasl
lmdb	Add support for using dev-db/lmdb for lookup tables
memcached	Add support for using net-misc/memcached for lookup tables
vda	Add support for virtual delivery agent quota enforcing

qmail-ldap

cluster	Enable this if you want to have cluster support in qmail-ldap
gencertdaily	Generate SSL certificates daily instead of hourly
highvolume	Prepare qmail for high volume servers
rfc2307	Add support for RFC2307 compliant uid/gid attributes
rfc822	Add support for RFC822 compliant mail attributes

qpsmtpd

postfix	create user with permissions for proper postfix interaction

ssmtp

mta	Install symlinks for sendmail-compatible MTA.

mate-base

caja

gtk3	Build with GTK+3 instead of GTK+2
mate	Install x11-themes/mate-icon-theme which is needed when this package is used in the MATE desktop environment.
packagekit	Enable support for installing via app-admin/packagekit based on mimetype

libmatekbd

gtk3	Build with GTK+3 instead of GTK+2

mate

base	Install base MATE Desktop applications that are recommended for the most common usage; for example, this installs the file manager. Disable this and other USE flags if you want a more minimal MATE Desktop.
extras	Install additional MATE Desktop applications that are recommended for extended usage of the MATE Desktop as upstream sees it; for example, this installs MATE Desktop's office related applications. Disable this if you plan to use your own non-MATE Desktop alternatives or a custom mixture of MATE and non-MATE packages.
gtk3	Build all of MATE DE with GTK+3 instead of GTK+2
help	Install gnome-extra/yelp to handle in application help menus and documentation browsing
notification	Force notification daemon to default to MATE's notification daemon. Enabled by default. Disable if it causes conflicts with other installed desktop environments.
themes	Install MATE Desktop's themes; if you use other themes, you can disable this to spare some space and time.

mate-applets

gtk3	Build with GTK+3 instead of GTK+2

mate-applets-meta

appindicator	Pull in mate-extra/mate-indicator-applet for AppIndicator applet
gtk3	Make sure applets are built with GTK+3 instead of GTK+2
netspeed	Pull in net-analyzer/mate-netspeed for net speed monitoring applet
sensors	Pull in mate-extra/mate-sensors-applet for hw sensors applet

mate-control-center

appindicator	Add support for AppIndicator
gtk3	Build with GTK+3 instead of GTK+2

mate-desktop

gtk3	Build with GTK+3 instead of GTK+2

mate-panel

gtk3	Build with GTK+3 instead of GTK+2

mate-session-manager

gtk3	Build with GTK+3 instead of GTK+2
xtrans	Build with Xtrans support; WARNING: Disabling this flag will result in ICE binding on all interfaces

mate-settings-daemon

gtk3	Build with GTK+3 instead of GTK+2

mate-extra

caja-extensions

cdr	Add an extension to burn files to cds using app-cdr/brasero.
gajim	Add an extension to support net-im/gajim.
gksu	Add an extension to support opening files as root with x11-libs/gksu.
gtk3	Build with GTK+3 instead of GTK+2
image-converter	Add image conversion support.
mail	Add an extension to support e-mail functionality.
open-terminal	Add an extension to support an open terminal.
pidgin	Add an extension to support net-im/pidgin
share	Add an extension to support sharing files.
wallpaper	Add an extension to support setting an image as the current wallpaper

mate-indicator-applet

gtk3	Build with GTK+3 instead of GTK+2

mate-media

gtk3	Build with GTK+3 instead of GTK+2

mate-netbook

gtk3	Build with GTK+3 instead of GTK+2

mate-polkit

accountsservice	Support extraction of data from AccountsService
appindicator	Add support for AppIndicator
gtk3	Build with GTK+3 instead of GTK+2

mate-power-manager

applet	Enable building of the MATE applet.
gtk3	Build with GTK+3 instead of GTK+2
man	Build power manager's man page.
pm-utils	Adds support for suspend/resume using sys-power/upower-pm-utils instead of sys-power/upower

mate-screensaver

consolekit	Enable support for sys-auth/consolekit
gtk3	Build with GTK+3 instead of GTK+2

mate-sensors-applet

gtk3	Build with GTK+3 instead of GTK+2

mate-system-monitor

gtk3	Build with GTK+3 instead of GTK+2

mate-user-share

gtk3	Build with GTK+3 instead of GTK+2

mate-utils

applet	Enable the mate dictionary applet
gtk3	Build with GTK+3 instead of GTK+2

media-fonts

corefonts

tahoma	Also install the Tahoma font. Due to the lack of a free bold variant, this may render badly. See bug 184790.

culmus

ancient	Install ancient semitic scripts
fancy	Install fancy fonts
fontforge	Use media-gfx/fontforge to build fonts from source
taamey	Install taamey fonts

dejavu

fontforge	Use media-gfx/fontforge to build fonts from source

fontawesome

otf	Install the OpenType version of the font
ttf	Install the TrueType version of the font

infinality-ultimate-meta

free	Install fonts for the "free" preset
latin	Install additional latin fonts
minimal	Install a minimal set of fonts
ms	Install (free) fonts for the "ms" preset

intlfonts

bdf	Installs BDF fonts in addition to PCF

liberation-fonts

fontforge	Use media-gfx/fontforge to build fonts from source

montecarlo

bdf	Install BDF fonts in addition to PCF

mplus-outline-fonts

ipafont	Generates new fonts merged with media-fonts/ja-ipafonts

sil-charis

compact	Use more compactly spaced font

sil-gentium

compact	Also install more compact version of the font.

terminus-font

a-like-o	Changes view of letter 'a' - a looks like o (see homepage)
center-tilde	Place the '~' character vertically centered on the line instead of to the top.
distinct-l	ll2 variant with more distinctive l (lowercase L)
pcf	Install Portable Compiled Font (PCF) (required for X11)
pcf-unicode-only	Remove non-unicode PCF fonts that could be problematic. See bug #520222.
psf	Install PC Screen Font (PSF) with unicode data (for linux console)
quote	Changes view of quotes: symmetric ` and ' instead of asymmetric one (see homepage)
raw-font-data	Install RAW font data which should be compatible with most UNIX systems (you don't need this on linux)
ru-dv	Changes view of Russian letters 'de' and 've' (see homepage)
ru-g	Changes view of Russian letter 'ge' (see homepage)
ru-i	Changes view of Russian letter 'i' - not like Latin u, but like "mirrored" N (see homepage)
ru-k	Changes view of Russian letter 'k' (see homepage)

unifont

fontforge	Use media-gfx/fontforge to build fonts from source
utils	Install unifont utilities

media-gfx

album

plugins	Install optional plugins
themes	Install optional themes

asymptote

boehm-gc	Enables using the Boehm-Demers-Weiser conservative garbage collector
offscreen	Enables off-screen rendering
sigsegv	Enables using dev-libs/libsigsegv

blender

boost	Enable features depending on boost.
bullet	Enable Bullet (Physics Engine).
collada	Add support for Collada interchange format through media-libs/opencollada.
colorio	Enable OpenColorIO color management through media-libs/opencolorio.
cuda	Build cycles renderer with nVidia CUDA support.
cycles	Build cycles renderer (requires media-libs/openimageio and dev-libs/boost).
dds	Adds DDS textures support to Blender.
doc	Build C and Python API documentation directly from the source code.
elbeem	Adds surface fluid simulation to Blender using El'Beem library.
game-engine	Adds Game Engine support to Blender.
headless	Build without graphical support (renderfarm, server mode only).
jemalloc	Use dev-libs/jemalloc for memory allocation.
llvm	Enable features depending on llvm.
man	Build and install man pages.
ndof	Enable NDOF input devices (SpaceNavigator and friends).
openimageio	Enable OpenImageIO Support
opennl	Enable use of Open Numerical Library
opensubdiv	Add rendering support form OpenSubdiv from Dreamworks Animation through media-libs/opensubdiv.
openvdb	Add GPU preview rendering. Only works with nVidia cards.
player	Build the Blender Player. THis requires the Game engine.
redcode	This flag add support for RED CODE camera digital format (5K HD images *.r3d) - EXPERIMENTAL.
test	Build the provided unit tests.
valgrind	Add support for memory debugging using dev-util/valgrind

comix

rar	Pulls app-arch/unrar for rar file support

cura

usb	Access 3D printers via USB

darktable

colord	Support color management using x11-misc/colord
flickr	Add support for uploading photos to flickr
geo	Enable geotagging support
kwallet	Enable encrypted storage of passwords with kde-frameworks/kwallet
libsecret	Enable libsecret support to store login credentials
opencl	Enable opencl support
pax_kernel	Triggers paxmarking of main darktable binary
webp	Enable WebP export support

digikam

addressbook	Enable akonadi contact integration
kipi	Enable support for media-plugins/kipi-plugins
lensfun	Enable support for media-libs/lensfun
marble	Enable support for geolocation using kde-apps/marble
panorama	Build the panorama plugin which requires media-gfx/hugin
semantic-desktop	Enable kde-frameworks/kfilemetadata support

enblend

gpu	GPU support for Enblend
image-cache	allow for processing of large images

eog-plugins

flickr	Enable uploading to Flickr
map	Enable world map display using media-libs/libchamplain
picasa	Enable uploading to Google's Picasa Web Albums

eom

gtk3	Build with GTK+3 instead of GTK+2

exact-image

swig	Adds Swig support dev-lang/swig

exiv2

webready	Support reading metadata over the internet

fbida

X	Install the Motif based image viewer "ida"
fbcon	Install the framebuffer image viewer "fbi"
ghostscript	Install the framebuffer ghostscript viewer "fbgs"
webp	Enable support for the WebP image format

fim

dia	Enable DIA file support via app-office/dia
imagemagick	Use convert from media-gfx/imagemagick as fallback file opener
xfig	Enable FIG file support via media-gfx/xfig

fontforge

truetype-debugger	Enable truetype debugger in fontforge

fotowall

webcam	Enable webcam support

freewrl

glew	Enable glew extensions
java	Build and install java EAI/SAI support library
libeai	Build EAI C library
opencl	Enable OpenCL support
osc	Allows for OSC-based control and communication between multiple freewrl instances
rbp	Enable support for Rigid Body Physics

geeqie

gpu-accel	Enable GPU acceleration support - experimental
gtk3	Link against x11-libs/gtk+:3 instead of x11-libs/gtk+:2
map	Enable items map display - experimental

gimp

smp	Enable support for multiprocessors
vector-icons	Enable support for vector icons (experimental)

gmic

cli	Build CLI interface
opencv	Enable support for webcams using the OpenCV library

gnome-photos

flickr	Ensure runtime Flickr support

graphicsmagick

fpx	Enable FlashPix support with media-libs/libfpx
modules	Compile graphicsmagick with dynamically loadable modules
q16	Set storage quantum size to 16 (~2*memory)
q32	Set storage quantum size to 32 (~5*memory)
webp	Enable support for webp image format

graphviz

X	Builds lefty front-end, builds plugin -Txlib, and enables support for x11 in various other modules (needs cairo)
devil	Enables DevIL output plugin -Tdevil
gdk-pixbuf	Enables gdk-pixbuf2 plugin
gtk	Enables gtk+ output plugin -Tgtk (needs cairo)
gts	Enables support for gts
lasi	Enables PostScript output via media-libs/lasi, for plugin -Tlasi (needs cairo)
qt4	Builds gvedit front-end

gthumb

http	Enable webservice integration through net-libs/libsoup
json	Compile code that uses the libjson-glib library
slideshow	Enable slideshow plugin
webp	Enable support for webp image format

hugin

sift	automatically align images with media-gfx/autopano-sift-C

imagemagick

autotrace	Use media-gfx/autotrace to convert bitmaps into vector graphics
corefonts	Use media-fonts/corefonts which is required by some commands
fpx	Enable media-libs/libfpx support
hdri	enable High Dynamic Range Images formats
lqr	Enable experimental liquid rescale support using media-libs/liblqr
opencl	Enable OpenCL support
pango	Enable Pango support using x11-libs/pango
q32	Set quantum depth value to 32
q64	Set quantum depth value to 64
q8	Set quantum depth value to 8
webp	Enable webp image format support using media-libs/libwebp

imageworsener

webp	enable webp image format support

inkscape

cdr	Enable support for CorelDRAW Diagrams
dia	pull in app-office/dia for dia import extension
inkjar	Enable support for OpenOffice.org SVG jar files
latex	pull in dependencies for LaTeX formulas
visio	Enable support for Microsoft Visio Diagrams
wpg	Enable support for WordPerfect Graphics

iscan-plugin-gt-f500

minimal	Install the firmware only, and not the plugin.

jpeg2ps

metric	Default to A4 paper size

k3d

3ds	Enable support for 3D Studio models
cuda	Use nvidia cuda toolkit for speeding up computations
gts	Add Support for the GNU Triangulated Surface Library sci-libs/gts

kphotoalbum

face	Enable face detection and recognition using kde-apps/libkface
kipi	Support for the KDE Image Plugin Interface
map	Enable map display support using kde-apps/libkgeomap

krita

color-management	Enable color management via media-libs/opencolorio
qtmedia	Enable sound support for animations via dev-qt/qtmultimedia
vc	Enable support for dev-libs/vc, could be a significant speed boost

librecad

3d	Require all 2D coordinates stored as 3D
tools	Build additional tool programs: tff2lff

luminance-hdr

fits	Enable support for the FITS format

nip2

goffice	use x11-libs/goffice to show plots

nomacs

opencv	Build support for media-libs/opencv
zip	Build support for zip archives

nvidia-texture-tools

cg	Enable NVIDIA C graphics compiler toolkit plug-in
cuda	Enable NVIDIA CUDA toolkit support
glew	Enable support for The OpenGL Extension Wrangler Library (media-libs/glew)

openclipart

gzip	Compresses clip art using gzip

openexr_viewers

cg	Add support for nvidia's cg shaders

openvdb

abi3-compat	Enables compatibility with the old 3.x ABI. enabled by dfault.
openvdb-compression	Adds enhanced compression to files through dev-libs/c-blosc. Very useful so enabled by dfault.

photoqt

exiv2	Use media-gfx/exiv2 as optional dependency

pngcrush

system-libs	Use libpng and libz provided by system

potrace

metric	default to a4 paper size and metric measurement

povray

io-restrictions	POV-Ray's mechanism for control of I/O operations
mkl	Enable support for Intel Vector Math Library, part of sci-libs/mkl

pqiv

archive	Enable support for images in archives and cbX comic book files

pstoedit

emf	Enable media-libs/libemf support
flash	Enable media-libs/ming SWF support
pptx	Enable support for generating PowerPoint pptx files

qiv

magic	Use libmagic to determine mimetypes

qiviewer

webp	Build support for WEBP image format

simple-scan

colord	Support color management using x11-misc/colord

slic3r

gui	Enable GUI

splashutils

fbcondecor	Support for the fbcondecor kernel patch.

ufraw

contrast	enable contrast setting option
fits	Enable support for the FITS image format through sci-libs/cfitsio
timezone	enable DST correction for file timestamps

xpaint

pgf	Support for loading PGF images

xsane

ocr	Enable support for Optical Character Recognition reader

yafaray

blender	install media-gfx/blender scripts

media-libs

a52dec

djbfft	Prefer D.J. Bernstein's library for fourier transforms

allegro

dumb	Enable media-libs/dumb module library support
physfs	Enable physfs support
vga	Enables the VGA graphics driver

alsa-lib

alisp	Enable support for ALISP (ALSA LISP) interpreter for advanced features.

alure

dumb	Enable media-libs/dumb module library support
fluidsynth	Enables Fluidsynth MIDI software synthesis

assimp

boost	Build assimp with boost support
samples	Build viewer library
tools	Build assimp tool binary

aubio

double-precision	Compile in double precision mode.

avidemux-core

system-ffmpeg	Use the ffmpeg provided by the system.

avidemux-plugins

aften	Enable A/52 (AC-3) audio encoder support.
amr	Enable Adaptive Multi-Rate format support via media-libs/opencore-amr.
fribidi	Enable unicode bidirectional algorithm support via dev-libs/fribidi.
twolame	Enable TwoLAME support via media-sound/twolame, an optimised MPEG Audio Layer 2 (MP2) encoder.
vpx	Enable WebM VP8 Codec SDK support via media-libs/libvpx.

babl

cpu_flags_x86_f16c	Take advantage of CPU feature f16c

cal3d

16bit-indices	Enables use of 16bit indices

chromaprint

tools	Build and install fpcalc and fpcollect tools

clutter

egl	Enable EGL backend.
gtk	Use gdk-pixbuf from x11-libs/gtk+ as image rendering backend

cogl

gles2	Enable OpenGL ES 2.0 support
kms	Enable KMS support.
pango	Build cogl-pango library for x11-libs/pango integration

coin

simage	Texture loading via media-libs/simage library

devil

allegro	Add support for Allegro
nvtt	Add support for media-gfx/nvidia-texture-tools

elementary

quicklaunch	Enable quick-launch support

embree

imagemagick	Enables BMP, GIF, PNG, TGA, TIFF image codecs.
ispc	Enables support for the Intel SPMD Program Compiler.
jpeg	Enables JPEG image codecs.
openexr	Enables OpenEXR image codecs.
png	Enables PNG image codecs.

esdl

image	Enable image support

faad2

digitalradio	Digital Radio Mondiale (warning: disables other decoders)

flickcurl

raptor	Use media-libs/raptor for proper RDF serializing

fontconfig-infinality

nyx	Additional style using croscorefonts

freetype

adobe-cff	Use Adobe CFF as default font-renderer
bindist	Disable ClearType support (see http://freetype.org/patents.html)
bzip2	Support bzip2 compressed PCF fonts.
cleartype_hinting	New bytecode hinting mode for TrueType fonts that activates subpixel hinting (a.k.a. ClearType hinting) by default
fontforge	Install internal headers required for TrueType debugger in media-gfx/fontforge (built with USE=truetype-debugger)
harfbuzz	Use media-libs/harfbuzz for auto-hinting OpenType fonts. WARNING: may trigger circular dependencies!
infinality	Enable infinality options for improved LCD filtering
utils	Install utilities and examples from ft2demos

freeverb3

audacious	Build Audacious plugin
forcefpu	Disable assembly code
plugdouble	Build plugins in double precision mode (default is float)

ganv

fdgl	Use experimental force-directed graph layout

gd

webp	Enable support for the webp format

gegl

lensfun	Enable support for media-libs/lensfun.
umfpack	Enable sparse solving via sci-libs/umfpack.
webp	Enable support for media-libs/libwebp

giflib

rle	Build converters for RLE format (utah raster toolkit)

gmtk

dconf	Enable support for gnome-base/dconf

grilo

network	Enable network access for media discovery using net-libs/libsoup
playlist	Enable support for playlists through dev-libs/totem-pl-parser

gst-plugins-bad

bzip2	Enable bzip2 encoder/decoder plugin
egl	Enable EGL support
gles2	Enable GLES2 support

gst-plugins-base

ivorbis	Enable integer based vorbis decoder
pango	Enable pango GStreamer plugin

gstreamer

orc	Disable some PaX memory protections to allow plugins that use dev-lang/orc for runtime optimization to be used on hardened PaX systems
unwind	Enable sys-libs/libunwind usage for better backtrace support in leaks tracer module

harfbuzz

glib	Compile with GLib Unicode support
graphite	Use graphite to render complex non-Roman writing systems

jbig2enc

webp	Add support for WEBP image format

leptonica

utils	Install command-line utilities
webp	Adds support for the WebP image format

libafterimage

shaping	Use MIT shaped X windows extention.
shm	Use MIT shared memory extention for X image transfer.

libass

harfbuzz	Enables OpenType shaping via media-libs/harfbuzz.

libbdplus

aacs	Add support for decryption of AACS

libbluray

aacs	Add support for decryption of AACS
bdplus	Use media-libs/libbdplus for BD+ decryption
java	Add support for BD-J
udf	Add UDF (Universal Disk Format) support
utils	Install command-line utilities and examples

libcanberra

alsa	Enables ALSA sound driver.
gstreamer	Enables gstreamer sound driver. Not useful when alsa or pulseaudio is available.
gtk	Enables building of gtk+ helper library, gtk+ runtime sound effects and the canberra-gtk-play utility. To enable the gtk+ sound effects add canberra-gtk-module to the colon separated list of modules in the GTK_MODULES environment variable.
gtk3	Enables building of gtk+3 helper library, gtk+3 runtime sound effects and the canberra-gtk-play utility. To enable the gtk+3 sound effects add canberra-gtk-module to the colon separated list of modules in the GTK_MODULES environment variable.
pulseaudio	Enables PulseAudio sound driver that should be able to support positional event sounds. This is the preferred choice for best sound events experience and picked by default if compiled in and possible to use at runtime.
sound	Install x11-themes/sound-theme-freedesktop to get sounds on Gnome and Xfce.
tdb	Enables Trivial Database support for caching purposes.

libde265

tools	Install addtional tools, require USE=qt4 or qt5

libextractor

archive	Enable archive support using app-arch/libarchive
gsf	Enable OLE2 (MS Office) plug-in support using gnome-extra/libgsf
magic	Enable magic support using sys-apps/file
midi	Enable MIDI support through media-libs/libsmf

libggi

vis	Enables sparc vis support for libggi

libgphoto2

serial	Enable serial port support

libgpod

gtk	Enable ArtworkDB support

libgroove

chromaprint	Enable audio fingerprinting using media-libs/chromaprint.
loudness	Enable loudness detection according to the EBU R128 standard using media-libs/libebur128.
sound	Enable audio playing.

liblastfm

fingerprint	Build the lastfm-fingerprint library

libmp4v2

utils	Install command-line utilities

libmypaint

gegl	Add support for media-libs/gegl

libomxil-bellagio

audioeffects	enable audio volume/mixer effects components
clocksrc	enable clock component
videoscheduler	enable xvideosink video scheduler

libpagemaker

tools	Build command line file format conversion tools

libpng

apng	support unofficial APNG (Animated PNG) spec

libpostproc

pic	Force shared libraries to be built as PIC (this is slower).

libquicktime

schroedinger	Enable Dirac video support (an advanced royalty-free video compression format) via libschroedinger (high-speed implementation in C of the Dirac codec)

libraw

demosaic	Enable support for external interpolation algorithms

libsdl

joystick	Control joystick support (disable at your own risk)
sound	Control audio support (disable at your own risk)
tslib	Build with tslib support for touchscreen devices
video	Control video support (disable at your own risk)

libsdl2

fusionsound	use FusionSound audio driver
gles	include OpenGL ES support
haptic	Enable the haptic (force feedback) subsystem
joystick	Control joystick support (disable at your own risk)
sound	Control audio support (disable at your own risk)
tslib	Build with tslib support for touchscreen devices
video	Control video support (disable at your own risk)

libvisio

tools	Build conversion tools

libvpx

highbitdepth	Enable 10 and 12 bit support for VP9.
postproc	Enable additional post processing filters
svc	Enable spatial-svc support (experimental)

libwebp

experimental	Build with -DWEBP_EXPERIMENTAL_FEATURES
swap-16bit-csp	Enable byte swapping for 16 bit colorspace

libyami

dmabuf	Enable dma_buf buffer sharing.
egl	Enable EGL support.
md5	Add support for generating md5 sums for each frame.
v4l	Add support for V4L2 hardware codecs.

libzmf

tools	Build conversion tools

lilv

dyn-manifest	Add LV2 Dynamic Manifest support. See http://lv2plug.in/ns/ext/dynmanifest/

lv2

plugins	Enables examples plugins.

lvtk

gtk2	Enable x11-libs/gtk+:2 based GUI support
tools	Compile and install ttl2c tool

mediastreamer

amr	Use of AMR Narrow Band codec plugin
filters	Enable compilation of filters
g726	Support g726 codec
g729	Use g726 codec plugin
ilbc	Use of iLBC (RFC3951) codec plugin
ntp-timestamp	Turn on NTP timestamping on received packet
opus	Enable opus codec support
ortp	Enable usage of net-libs/ortp
pcap	Enable usage of net-libs/libpcap
silk	Use silk (skype protocol) codec plugin
video	Enable video support

mesa

bindist	Disable patent-encumbered ARB_texture_float, EXT_texture_shared_exponent, and EXT_packed_float extensions.
classic	Build drivers based on the classic architecture.
d3d9	Enable Direct 3D9 API through Nine state tracker. Can be used together with patched wine.
dri3	Enable DRI3 support.
egl	Enable EGL support.
gallium	Build drivers based on Gallium3D, the new architecture for 3D graphics drivers.
gbm	Enable the Graphics Buffer Manager for EGL on KMS.
gcrypt	Use dev-libs/libgcrypt for low level sha1 utility functions.
gles1	Enable GLESv1 support.
gles2	Enable GLESv2 support.
libressl	Use dev-libs/libressl for low level sha1 utility functions.
llvm	Enable LLVM backend for Gallium3D.
nettle	Use dev-libs/nettle for low level sha1 utility functions.
opencl	Enable the Clover Gallium OpenCL state tracker.
openmax	Enable OpenMAX video decode/encode acceleration for Gallium3D.
openssl	Use dev-libs/openssl for low level sha1 utility functions. May cause issues with games from Steam.
osmesa	Build the Mesa library for off-screen rendering.
pax_kernel	Enable if the user plans to run the package under a pax enabled hardened kernel
pic	disable optimized assembly code that is not PIC friendly
unwind	Add support for stack trace unwinding and function name resolution
valgrind	Compile in valgrind memory hints
vdpau	Enable the VDPAU acceleration interface for the Gallium3D Video Layer.
vulkan	Enable Vulkan drivers
wayland	Enable support for dev-libs/wayland
xa	Enable the XA (X Acceleration) API for Gallium3D.
xvmc	Enable the XvMC acceleration interface for the Gallium3D Video Layer.

mlt

compressed-lumas	Compress the luma files in png.
frei0r	Build the module for media-plugins/frei0r-plugins
kdenlive	Build support for kde-apps/kdenlive
lua	Build SWIG bindings for Lua
melt	Build the melt commandline tool
opencv	Build motion tracking module using media-libs/opencv
python	Build SWIG bindings for Python
rtaudio	Builds rtaudio consumer for native audio support on multiple platforms.
ruby	Build SWIG bindings for Ruby

netpbm

rle	Build converters for the RLE format (utah raster toolkit)

opencolorio

pdf	Install extra documentation in PDF format

opencv

contrib	Install user contributed scripts from opencv_contrib (Experimental!)
contrib_cvv	CVV module requires Qt5
contrib_hdf	HDF module requires sci-libs/hdf5
contrib_sfm	SFM module requires eigen, gflags, and glog
contrib_xfeatures2d	Enables xfeatures2d and autodownload of samples in contrib
cuda	Enable NVIDIA Cuda computations support (Experimental!)
eigen	Enable usage of dev-cpp/eigen for computations
gdal	Enable support for sci-libs/gdal library
gflags	Use Google's C++ argument parsing library
glog	Use Google's C++ loggin library
ipp	Enable Intel Integrated Primitive support
opencl	Add support for OpenCL
tesseract	Use Google's OCR Engine
testprograms	Build and install programs for testing OpenCV (performance)
vtk	Build new 3D visualization module viz based on sci-libs/vtk
webp	Enable support for webp image format

openh264

plugin	Install the Gecko Media Plugin (GMP) for use with Mozilla packages
utils	Install the CLI encoder and decoder utilities

openimageio

colorio	Use media-libs/opencolorio
opencv	Use media-libs/opencv
tbb	Use dev-cpp/tbb

opensubdiv

cuda	Enable NVIDIA CUDA Toolkit support through dev-util/nvidia-cuda-toolkit.
opencl	Enable OpenCL support through virtual/opencl.
ptex	Adds support for faster per-face texture mapping through media-libs/ptex.
tbb	Enable multithreading with the Intel Threads Building Blocks through dev-cpp/tbb.
tutorials -

opus

ambisonics	Enable ambisonics support (experimental).
custom-modes	Build with custom-modes.

opusfile

fixed-point	Enable fixed-point arithmetic operations
float	Enable floating point arithmetic operations
http	Enable http connections

phonon

designer	Install plugin for dev-qt/designer
vlc	Install VLC Phonon backend
zeitgeist	Add support for Zeitgeist event tracking system

phonon-gstreamer

network	Enable network streaming support via libsoup

portmidi

test-programs	Install various example programs

quvi

json	Enable support for JSON output

raptor

json	Enable support for JSON parsing

raspberrypi-userland-bin

hardfp	Use armv6 hardfp ABI

sdif

ftruncate	Enables usage of ftruncate v. truncate

sdl-image

webp	support loading WEBP images

sdl-mixer

fluidsynth	Use media-sound/fluidsynth for MIDI support
midi	basic support for MIDI files
mod	basic support for MOD files
playtools	Install playwave and playmus tools (useful for testing)
smpeg	Use media-libs/smpeg for MP3 support
wav	support WAVE files

sdl-sound

physfs	Enable physfs support

sdl2-image

webp	support loading WEBP images

sdl2-mixer

fluidsynth	Use media-sound/fluidsynth for MIDI support
midi	basic support for MIDI files
mod	basic support for MOD files
playtools	Install playwave and playmus tools (useful for testing)
smpeg	Use media-libs/smpeg for MP3 support
tremor	enable OGG Vorbis music via libtremor
wav	support WAVE files

sge

image	enable sdl-image support

silgraphite

pango	Enables the pango-graphite pango module.

spandsp

fixed-point	Enable fixed point support

speex

armv5te	Enables optimizations for armv5te processors.
utils	Enables speex commandline utilities (speexenc, speexdec).
vbr	Enable VBR support.

svgalib

kernel-helper	Build the helper kernel module

taglib

asf	Provide support for Microsoft's 'advanced systems format' media container.
boost	Use dev-libs/boost instead of GCC built-ins

tremor

low-accuracy	enable 32bit only multiply operations

vigra

valgrind	Enable valgrind in make check

vips

fits	Enable support for the FITS image format through sci-libs/cfitsio
matio	Enable support for reading images from Matlab files through sci-libs/matio

waffle

egl	Enable EGL support
gbm	Enable support for the Generic Buffer Manager (gbm)
wayland	Enable Wayland support

x264

10bit	Set output bit depth to 10, this may not be compatible with all decoders
interlaced	enable interlaced encoding support, this can decrease encoding speed by up to 2%
opencl	Add support for OpenCL.
pic	disable optimized assembly code that is not PIC friendly

x265

10bit	Add support for producing 10bits HEVC.
12bit	Add support for producing 12bits HEVC.
numa	Build with support for NUMA nodes.
pic	Disable optimized assembly code that is not PIC friendly
power8	Enable support for Power 8 assembly optimizations.

xine-lib

bluray	Enable playback of Blu-ray filesystems using media-libs/libbluray
dxr3	Enable support for DXR3 mpeg acceleration cards.
flac	Build the media-libs/flac based FLAC demuxer and decoder. This flag is not needed for playing FLAC content, neither standalone nor in Ogg container (OggFLAC), but might have better support for exotic features like 24-bit samples or 96kHz sample rates.
fusionsound	Enable support for the Fusion audio sub system
gtk	Build the gdkpixbuf-based image decoder plugin.
imagemagick	Build the ImageMagick-based image decoder plugin.
mad	Build the media-libs/libmad based mp3 decoder. This mp3 decoder has superior support compared to the one coming from FFmpeg that is used as a fallback. If you experience any bad behaviour with mp3 files (skipping, distorted sound) make sure you enabled this USE flag.
mmap	Use mmap() function while reading file from local disks. Using mmap() will use more virtual memory space, but leaves to the Kernel the task of caching the file's data. mmap() access should be faster, but might misbehave if the device where the file resides in is removed during playback.
truetype	Use media-libs/freetype for font rendering and media-libs/fontconfig for font discovery. Enabling this USE flag will allow OSD (such as subtitles) to use more advanced font and to more easily select which font to use. The support for TrueType fonts in xine-lib is still experimental, and might not be as good looking as the bitmap fonts used with this USE flag disabled.
vdr	Build the VDR plugin
vidix	Enable support for vidix video output.
vis	Adds support for SIMD optimizations for UltraSPARC processors.
vpx	Enable VP8 codec support via media-libs/libvpx.
xvmc	Enable support for XVideo Motion Compensation (accelerated mpeg playback).

xvid

pic	disable optimized assembly code that is not PIC friendly

media-plugins

audacious-plugins

adplug	Build with AdPlug (Adlib sound card emulation) support
bs2b	Enable Bauer Bauer stereophonic-to-binaural headphone filter
cue	Support CUE sheets using the libcue library
fluidsynth	Support FluidSynth as MIDI synth backend
gtk3	Link against version 3 of the GIMP Toolkit instead of version 2 (x11-libs/gtk+)
http	Support HTTP streams through neon
midi	Build with amidi-plug (MIDI synth) support
scrobbler	Build with scrobbler/LastFM submission support
sid	Build with SID (Commodore 64 Audio) support

calf

lv2	Add support for Ladspa V2

frei0r-plugins

facedetect	Enables building of facedetect plugin, which depends on media-libs/opencv
scale0tilt	Enables building of scale0tilt and vectorscope plugins, which depend on media-libs/gavl

gkrellmpc

threads	Use separate thread to init connection (unsafe)

grilo-plugins

chromaprint	Enable Chromaprint support
daap	Enable dmap support through net-libs/libdmapsharing
flickr	Enable Flickr support
freebox	Build support for viewing TV channels using Freebox
gnome-online-accounts	Enable net-libs/gnome-online-accounts support
pocket	Support for showing content from Pocket
subtitles	Enables support for subtitle from OpenSubtitles
thetvdb	Build support for thetvdb.com
tracker	Build support for content discovery using the app-misc/tracker indexer
vimeo	Build support for Vimeo content discovery using net-libs/libsoup and dev-libs/libgcrypt
youtube	Build support for YouTube content discovery using dev-libs/libgdata

gst-plugins-gl

libvisual	Enable visualization effects via media-libs/libvisual

gst-plugins-meta

http	Enable http streaming via net-libs/libsoup
libvisual	Enable visualization effects via media-libs/libvisual
opus	Enable Opus audio codec support
vpx	Enables vp8 codec support using libvpx, required to play some HTML5 videos

gst-plugins-vaapi

drm	Enable DRM renderer
egl	Enable EGL support

hexter

gtk2	Enable x11-libs/gtk+:2 based GUI

imlib2_loaders

eet	Enable Eet image loader
xcf	Enable XCF image loader

kipi-plugins

flashexport	Build the flash export plugin
mediawiki	Build the mediawiki export plugin
remotestorage	Build plugin for remote storage using network protocols such as FTP, SSH, SAMBA via kde-frameworks/kio
vkontakte	Build plugin for vkontakte.ru

mediastreamer-ilbc

20ms-frames	enable 20ms frame size (default is 30ms). Some VOIP providers such as Gizmo5 (aka Sipphone) require the codec to be compiled with the 30ms setting.

mythplugins

cdr	Allows MythMusic to burn CD-Rs
exif	Allows MythGallery to read EXIF data from photos
fftw	Adds visual effects to MythMusic when playing back music
hls	HTTP Live Streaming support
mytharchive	Allows you to archive recorded content to CD or DVD
mythbrowser	Adds a web browser within MythTV
mythgallery	Adds a picture viewing gallery within MythTV
mythgame	Adds a frontend to various ROM emulators within MythTV
mythmusic	Adds the ability for MythTV to act as a music player
mythnetvision	Adds the ability to view netvision devices within MythTV
mythnews	Adds a news viewer within MythTV
mythweather	Adds weather information within MythTV
mythzoneminder	Adds support for zoneminder (requires a server with the appropriate mythtv daemon somewhere on the network).
raw	Allows MythGallery to view photos saved in RAW format

vdr-burn

dvdarchive	DMH DVD - Archive

vdr-epgsearch

conflictcheckonly	ToDo
epgsearchonly	ToDo
quicksearch	ToDo
tre	Add support for unlimited fuzzy searching with help of dev-libs/tre library

vdr-graphtft

graphtft-fe	Install external x11 remote frontend
theme_avp	graphTFT Alien vs. Predato theme
theme_deepblue	graphTFT default theme
theme_deeppurple	graphTFT Deep Purple theme
theme_poetter	graphTFT Poetter theme
touchscreen	Enable Touchscreen support

vdr-music

graphtft	Enable support for media-plugins/vdr-graphtft

vdr-pvr350

yaepg	Enables full support for the output format of vdr-yaepg

vdr-streamdev

client	Compile the VDR plugin vdr-streamdev-client that acts like a dvb-budget card
server	Compile the VDR plugin vdr-streamdev-server that allows remote systems to access the DVB cards used for the local VDR

vdr-text2skin

contrib	Install user contributed scripts

vdr-vdrmanager

stream	Add support for streaming Video to Android client

vdr-weatherng

dxr3	enables lower osd color depth for dxr3 cards

vdr-xine

yaepg	Enables support for the plugin vdr-yaepg (showing scaled video besides OSD)

vdr-xineliboutput

bluray	Enable BluRay metadata support through media-libs/libbluray
cec	Enable CEC support through dev-libs/libcec
libextractor	Use media-libs/libextractor to gather files' metadata in media-player
vdr	Compile the vdr output plugin to use local or remote xine as output
xine	Compile the xine input plugin for displaying vdr video and OSD

media-radio

ax25-tools

X	Enable some X based configuration tools.

fldigi

hamlib	Enables support by the Hamlib amateur radio rig control library to get/set frequency and mode of the ham radio in use

tucnak2

ftdi	Enable support for FTDI USB chips
hamlib	Enables support by the Hamlib amateur radio rig control library to get/set frequency and mode of the ham radio

unixcw

ncurses	Enables building the curses based morse code tutor program 'cwcp'.

xastir

festival	Enable text to speech synthesizer
gdal	Support for some further map formats
geotiff	Install geotiff support. Allows using USGS DRG topo maps or other types of geotiff mapes/images

media-sound

abcde

id3tag	Support ID3, ID3v2 tagging of audio files
mac	Enable support for Monkey's Audio files
normalize	Add support for normalizing audio file volume levels
opus	Support opus encoding using opusenc
replaygain	Support for Replay Gain metadata, for relative volume adjustment

abcm2ps

pango	Use the pango library to render fonts with non-latin characters

alsa-utils

bat	install basic audio tester (BAT) util
libsamplerate	install utils that use libsamplerate (e.g. alsaloop)
ncurses	install utils that use ncurses (e.g. alsamixer)

alsaplayer

id3tag	Enables ID3 tagging with id3tag library

amarok

embedded	Use libmysqld, MySQL embedded server library. Try disabling this if you encounter -PIC related in amarok, it will make amarok rely only on standalone MySQL server.
lastfm	Enable Last.fm streaming services support through media-libs/liblastfm
mp3tunes	Enable mp3tunes integration
mtp	Enable support for libMTP (Plays4Sure) devices access through libmtp
ofa	Use media-libs/libofa to compute MusicDNS acoustic fingerprints (used by MusicBrainz)
utils	Build the utils - old media-sound/amarok-utils

amsynth

dssi	Enable support for DSSI Soft Synth Interface

aqualung

ifp	Enable support for iRiver iFP portable audio players
lua	Enable support for programmable title formatting with dev-lang/lua
mac	Enable support for decoding Monkey's Audio files
podcast	Enable podcast support
systray	Enable system tray support

ardour

lv2	Add support for Ladspa V2

ario

audioscrobbler	Enable song tracking via last.fm
idle	Enable experimental support for MPD's idle command to reduce bandwidth and cpu usage, requires MPD 0.14

asunder

mac	Support for creation of Monkey's Audio files (APE)
opus	Support for creation of Opus files

audacious

chardet	Try to handle non-UTF8 chinese/japanese/korean ID3 tags
gtk3	Link against version 3 of the GIMP Toolkit instead of version 2 (x11-libs/gtk+)

audacity

id3tag	Enables ID3 tagging with id3tag library
libsamplerate	Uses media-libs/libsamplerate as audio resampling library: Higher quality than the included resampler but lower quality and much slower than libsoxr.
libsoxr	Uses media-libs/soxr as audio resampling library: Higher quality and much faster than both the included resampler and libsamplerate.
lv2	Add support for Ladspa V2
midi	Enables MIDI support
portmixer	Enable the internal portmixer feature
sbsms	Enables sbsms library support for slower, more accurate pitch and tempo changing
soundtouch	Enables soundtouch library support for pitch and tempo changing
twolame	Enables twolame support (MPEG Audio Layer 2 encoder)
vamp	Enables vamp plugins support (Audio analysing plugins)
vst	Enable VST plugin support

beets

badfiles	Validate MP3 & FLAC files.
bpd	Enable support for media-sound/mpd server emulation
chroma	Enable support for acoustic fingerprinting plugin using media-libs/chromaprint
convert	Enable support for the convert plugin which makes it possible to transcode files
discogs	Enable support for the discogs API plugin
lastgenre	Enable support for importing music genres from last.fm tags
lastimport	Enable support for importing your last.fm playcounts
mpdstats	Enable support for collecting statistic about listening habits from media-sound/mpd
opus	Enable opus support in gstreamer-based replaygain
replaygain	Enable support for Replay Gain metadata calculation during import
thumbnails	Generate thumbnails for albums
web	Enable embedded webserver support through dev-python/flask

bluez-alsa

hcitop	Enable top-like monitoring tool for HCI

cantata

http-server	Enable internal HTTP server to play non-MPD files
replaygain	Enable ReplayGain support, for relative volume adjustments

clementine

amazoncloud	Enable Amazon cloud drive support
box	Enable filesharing via Box.com
dropbox	Enable Dropbox support
googledrive	Enable Google Drive support
lastfm	Use liblastfm for fetching song info, scrobbling and radio streams
moodbar	Enable moodbar support
projectm	Build with ProjectM visualization
seafile	Enable support for seafile: a file sync service
skydrive	Enable Skydrive support
udisks_legacy	Enable storage management support via legacy sys-fs/udisks:0
vkontakte	Enable vk.com support
wiimote	Enable support for Wii remote

cmus

cdio	use libcdio for CD support
cue	enable CUE sheet parsing
discid	enable reading the ID of the inserted CD
opus	enable support for media-libs/opusfile
pidgin	install support script for net-im/pidgin
tremor	use libivorbis from media-libs/tremor instead of media-libs/libvorbis

csound

beats	Build the beats score frontend
chua	Build the chua opcodes
csoundac	Build the CsoundAC extension module
double-precision	Use double-precision floating point for audio samples
dssi	Build the DSSI opcodes
fluidsynth	Build the fluidsynth opcodes
image	Build the image opcodes
keyboard	Build Virtual MIDI keyboard
linear	Build the linear algebra Opcodes
luajit	Use the lua just-in-time compiler dev-lang/luajit instead of dev-lang/lua
portmidi	Build the PortMIDI I/O module
samples	Install the HRTF datafiles for use with hrtfmove, hrtfmove2, hrtfstat, hrtfearly, and hrtfreverb
score	Build the alternative score parser
stk	Build the stk opcodes
tcl	Build the tcl interface and clients
utils	Build stand-alone executables for utilities that can also be used via `csound -U`
websocket	Build the websocket opcode

darkice

aacplus	AAC+ encoding via media-libs/libaacplus
opus	Enable Opus audio codec support
twolame	Build with twolame support

denemo

fluidsynth	Enable Fluidsynth MIDI software synthesis
portmidi	Enable support for the portmidi backend

dir2ogg

mac	Add support for decoding Monkey's Audio files
wma	Add support for wma files through mplayer

drumstick

fluidsynth	Enable support for media-sound/fluidsynth

easytag

opus	Enable support for media-libs/opus and media-libs/opusfile (opus audio codec)

ecasound

lv2	Add support for Ladspa V2
oil	Use dev-libs/liboil for inner loop optimizations

fapg

xspf	Enable support for saving XSPF playlists.

forked-daapd

itunes	Enable support for iTunes library XML
lastfm	Enable LastFM scrobbling support
mpd	Enable streaming to mpd

frescobaldi

portmidi	Enable media-libs/portmidi support

gejengel

audioscrobbler	Enable track submission on last.fm

gimmix

cover	Enable cover art fetching
lyrics	Enable lyric fetching

gmpc

unique	Enable single instance support using dev-libs/libunique
xspf	Enable support for reading and saving XSPF playlists

gmusicbrowser

extras	Install some extra deps for plugins (ex. Titlebar)

gogglesmm

opus	Enable support for opus codec

google-musicmanager

log	Enables advanced logging through dev-libs/log4cxx

herrie

http	Enable http streaming
xspf	Enable support for reading and saving XSPF playlists

hydrogen

archive	Use libarchive instead of libtar

jack-audio-connection-kit

coreaudio	Build the CoreAudio driver on Mac OS X systems
cpudetection	Enables runtime cpudetection
pam	Add basic realtime configuration via sys-auth/realtime-base

jack2

celt	Support CELT low delay audio codec (media-libs/celt)
classic	Enable building of jackd"
opus	Support media-libs/opus
pam	Add basic realtime configuration via sys-auth/realtime-base

jalv

gtk2	Adds support for GTK+2 in addition to GTK+3 controlled by the gtk useflag.
gtkmm	Adds support for dev-cpp/gtkmm: C++ interface for GTK+2

kid3

acoustid	Enable support for acoustic fingerprinting plugin using (media-libs/chromaprint)

klick

rubberband	Enable rubberband support

lame

frontend	Build and install the 'lame' executable frontend to lame libraries.
mp3rtp	Build the mp3-to-RTP streaming utility. **UNSUPPORTED**

lilypond

guile2	Enable experimental support for Guile 2

linuxsampler

lv2	Add support for Ladspa V2

lmms

fluidsynth	Enables Fluidsynth MIDI software synthesis plugin.
libgig	Enables GIG player plugin.
soundio	Enalbes libsoundio support.
stk	Enables STK Mallet plugin.
vst	Enables the VeSTige plugin to run VST plugins through Wine.

lyvi

mpris	Enable MPRIS support

mangler

espeak	Text to speech engine
g15	Logitech g15 lcd support
opus	Codec specialized for speech over the internet

mixxx

hid	Enable HID controller support
shout	Enable broadcasting support via media-libs/libshout
vamp	Enable vamp analyzing plugins support

moc

cache	Enable tags caching support
magic	Use libmagic to determine mimetypes
sid	Build with SID (Commodore 64 Audio) support
tremor	Build vorbis support using an integer implementation of the vorbis library (media-libs/tremor)

mp3blaster

sid	Build with SID (Commodore 64 Audio) support

mp3splt-gtk

audacious	Include media-sound/audacious support

mpd

adplug	Enable the AdPlug decoder plugin
cdio	Use libcdio for ISO9660 parsing support
curl	Support for web stream listening
eventfd	Use the eventfd function in MPD's event loop
faad	Use external faad library for AAC decoding
fifo	Support writing audio to a FIFO
fluidsynth	Enables Fluidsynth MIDI software synthesis (discouraged)
glib	Enable GLib usage
gme	Enables support for media-libs/game-music-emu for playing various video game music formats.
id3tag	Support for ID3 tags
inotify	Use the Linux kernel inotify subsystem to notice changes to mpd music library
lame	Support for MP3 streaming via Icecast2
libmpdclient	Enable support for remote mpd databases
libsoxr	Enable the libsoxr resampler
mpg123	Enable support for mp3 decoding over media-sound/mpg123
network	Enables network streaming support
nfs	Enable support for the Network File System
opus	Enable Opus codec support
pipe	Support writing audio to a pipe
recorder	Enables output plugin for recording radio streams
sid	Build with SID (Commodore 64 Audio) support
signalfd	Use the signalfd function in MPD's event loop
soundcloud	Build plugin to access soundcloud
systemd	Enable support for systemd socket activation
twolame	Support twolame MPEG-2 encoding
wildmidi	Enable MIDI support via wildmidi
zip	Support for ZIP files

mpfc

wav	Enable wav audio codec support

mpg123

int-quality	Use rounding instead of fast truncation for integer output, where possible

mumble

g15	Enable support for the Logitech G15 LCD (and compatible devices).
speech	Enable text-to-speech support in Mumble.

murmur

ice	Use dev-libs/Ice to enable remote control capabilities.

ncmpc

artist-screen	Enable artist screen
chat-screen	Enable the chat screen
colors	Enable color support
help-screen	Enable the help screen
key-screen	Enable key editor screen
lyrics-screen	Enable lyrics screen
mouse	Enable curses getmouse support
search-screen	Enable search screen
song-screen	Enable song viewer screen

ncmpcpp

clock	Enable clock screen
outputs	Enable outputs screen
visualizer	Enable visualizer screen with sound wave/frequency spectrum modes

patchage

jack-dbus	Use Jack via D-Bus instead of libjack
session	Include experimental Jack session management (save/restore) support

pianobooster

fluidsynth	Enable Fluidsynth MIDI software synthesis

picard

acoustid	Use media-libs/chromaprint for acoustic fingerprinting

pithos

appindicator	Enable usage of appindicator to export menu options in to unity
keybinder	Use keybinder to enable global key bindings

pms

regex	Enable regular expression searches

podcatcher

bittorrent	Enable support for bittorrent downloads

potamus

opus	Adds support for the Opus codec.

pragha

glyr	Enable music metadata searchengine support using media-libs/glyr
grilo	Play songs on DLNA servers using media-libs/grilo
keybinder	Enable shortcut support using dev-libs/keybinder
lastfm	Enable last.fm support using media-libs/libclastfm
peas	Enable various plugins that will pull in dev-libs/libpeas as a dependency
playlist	Enable enhanced playlist support using dev-libs/totem-pl-parser
rygel	Share music on DLNA using net-misc/rygel
soup	Search metadata on AcoustID and radios on TuneIn using net-libs/libsoup

puddletag

acoustid	Use media-libs/chromaprint for acoustic fingerprinting
cover	Enables editing of FLAC cover art
musicbrainz	Enables support for musicbrainz, needs dev-python/python-musicbrainz
quodlibet	Enables support for editing media-sound/quodlibet databases

pulseaudio

X	Build the X11 publish module to export PulseAudio information through X11 protocol for clients to make use. Don't enable this flag if you want to use a system wide instance. If unsure, enable this flag.
alsa-plugin	Request installing media-plugins/alsa-plugins with PulseAudio plugin enabled. This ensures that clients supporting ALSA only will use PulseAudio.
asyncns	Use libasyncns for asynchronous name resolution.
doc	Build the doxygen-described API documentation.
equalizer	Enable the equalizer module (requires sci-libs/fftw).
gdbm	Use sys-libs/gdbm to store PulseAudio databases. Recommended for desktop usage. This flag causes the whole package to be licensed under GPL-2 or later.
glib	Add support to dev-libs/glib-based mainloop for the libpulse client library, to allow using libpulse on glib-based programs.
gnome	Use GConf to store user preferences on streams and so on. Don't enable this flag if you want to use a system wide instance. If unsure, enable this flag.
native-headset	Build with native HSP backend for bluez 5.
ofono-headset	Build with oFono HFP backend for bluez 5, requires net-misc/ofono.
oss	Enable OSS sink/source (output/input). Deprecated, upstream does not support this on systems where other sink/source systems are available (i.e.: Linux). The padsp wrapper is now always build if the system supports OSS at all.
realtime	Makes PulseAudio use RealtimeKit (sys-auth/rtkit) to get real-time priority while running.
ssl	Use dev-libs/openssl to provide support for RAOP (AirPort) streaming.
system-wide	Allow preparation and installation of the system-wide init script for PulseAudio. Since this support is only supported for embedded situations, do not enable without reading the upstream instructions at http://www.freedesktop.org/wiki/Software/PulseAudio/Documentation/User/WhatIsWrongWithSystemWide/ .
systemd	Build with sys-apps/systemd support to replace standalone ConsoleKit.
webrtc-aec	Uses the webrtc.org AudioProcessing library for enhancing VoIP calls greatly in applications that support it by performing acoustic echo cancellation, analog gain control, noise suppression and other processing.

qmidiarp

lv2	Enables Ladspa V2 plugins.

qmmp

analyzer	Enable visual analyzer
bs2b	Enable Bauer stereophonic-to-binaural headphone filter
cover	Enable album cover support
crossfade	Enable crossfade effect when switching tracks
cue	enable CUE sheet parsing
dbus	Enable DBus notifiications and MPRIS support
enca	Detects the character encoding automatically
game	Enable Game music support
gnome	Enable Gnome hotkey support (requires Qt5DBus)
lyrics	Fetch track lyrics from the web
midi	Enable midi support using wildmidi library
notifier	Enable qmmps' notifier system
opus	Enable the opus plugin