Add extra documentation (API, Javadoc, etc). It is recommended to enable per package instead of globally

Packages describing “doc” as local USE flag

Package “doc” Flag Description
dev-lisp/clx Builds documentation
net-firewall/nftables Create man pages for the package (requires app-text/asciidoc)
dev-python/icalendar Generate examples and other extra documentation
media-sound/pulseeffects Install packages needed to display built-in user documentation
dev-lisp/cmucl Installs package documentation
dev-libs/libp11 Generate and install API documentation for the package.
app-i18n/pyzy Generate API documentation
net-analyzer/cacti install html documentation
mail-client/alot Install user manual and API documentation
app-misc/muttprint Builds documentation
sys-devel/llvm Build and install the HTML documentation and regenerate the man pages
net-mail/notmuch Install API documentation
games-engines/solarus Install doxygen developer documentation.
app-emulation/open-vm-tools Generate API documentation
app-crypt/mit-krb5 Creates and installs the API and implementation documentation. This is only useful if you want to develop software which depends on kerberos
media-sound/easyeffects Install packages needed to display built-in user documentation
net-libs/c-client Install RFCs related to IMAP
net-analyzer/munin Build and install a local copy of the HTML documentation for the whole software. This requires dev-python/sphinx to process the documentation sources.
dev-libs/libunibreak Install html API documentation.
games-rpg/dreamweb High-resolution scans of the written material in the original UK game box
x11-misc/picom Build documentation and man pages (requires app-text/asciidoc)
sys-libs/ldb Builds documentation
media-libs/libpulse Build the doxygen-described API documentation.
dev-util/perf 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.
dev-libs/boost Install the full API documentation documentation. This takes over 200MB of extra disk space.
x11-misc/alock Build and install manpage with app-text/asciidoc.
app-portage/eix Create description of the eix cache file additionally in html format
x11-wm/stumpwm Include documentation
x11-wm/i3 Build and install the HTML documentation and regenerate the man pages

All packages providing a “doc” USE flag (2986)