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libxkbcommon

xkbcommon is a keymap compiler and support library which processes a reduced subset of keymaps as defined by the XKB specification. Primarily, a keymap is created from a set of Rules/Model/Layout/Variant/Options names, processed through an XKB ruleset, and compiled into a struct xkb_keymap, which is the base type for all xkbcommon operations.

From an xkb_keymap, an xkb_state object is created which holds the current state of all modifiers, groups, LEDs, etc, relating to that keymap. All key events must be fed into the xkb_state object using xkb_state_update_key(). Once this is done, the xkb_state object will be properly updated, and the keysyms to use can be obtained with xkb_state_key_get_syms().

Quick Guide

See Quick Guide.

API

While libxkbcommon's API is somewhat derived from the classic XKB API as found in X11/extensions/XKB.h and friends, it has been substantially reworked to expose fewer internal details to clients.

See the API Documentation.

Dataset

libxkbcommon does not distribute a keymap dataset itself, other than for testing purposes. The most common dataset is xkeyboard-config, which is used by all current distributions for their X11 XKB data. More information on xkeyboard-config is available here: http://www.freedesktop.org/wiki/Software/XKeyboardConfig

Relation to X11

Relative to the XKB 1.1 specification implemented in current X servers, xkbcommon has removed support for some parts of the specification which introduced unnecessary complications. Many of these removals were in fact not implemented, or half-implemented at best, as well as being totally unused in the standard dataset.

Notable removals:

  • geometry support
    • there were very few geometry definitions available, and while xkbcommon was responsible for parsing this insanely complex format, it never actually did anything with it
    • hopefully someone will develop a companion library which supports keyboard geometries in a more useful format
  • KcCGST (keycodes/compat/geometry/symbols/types) API
    • use RMLVO instead; KcCGST is now an implementation detail
    • including pre-defined keymap files
  • XKM support
    • may come in an optional X11 support/compatibility library
  • around half of the interpret actions
    • pointer device, message and redirect actions in particular
  • non-virtual modifiers
    • core and virtual modifiers have been collapsed into the same namespace, with a 'significant' flag that largely parallels the core/virtual split
  • radio groups
    • completely unused in current keymaps, never fully implemented
  • overlays
    • almost completely unused in current keymaps
  • key behaviors
    • used to implement radio groups and overlays, and to deal with things like keys that physically lock; unused in current keymaps
  • indicator behaviours such as LED-controls-key
    • the only supported LED behaviour is key-controls-LED; again this was never really used in current keymaps

Notable additions:

  • 32-bit keycodes
  • extended number of modifiers
  • extended number of groups
  • multiple keysyms per level
    • this requires incompatible dataset changes, such that X11 would not be able to parse these

Development

An extremely rudimentary homepage can be found at http://xkbcommon.org

xkbcommon is maintained in git at https://github.com/xkbcommon/libxkbcommon

Patches are always welcome, and may be sent to either xorg-devel@lists.x.org or wayland-devel@lists.freedesktop.org

Bugs are also welcome, and may be reported either at Bugzilla https://bugs.freedesktop.org/describecomponents.cgi?product=libxkbcommon or Github https://github.com/xkbcommon/libxkbcommon/issues

The maintainers are

Credits

Many thanks are due to Dan Nicholson for his heroic work in getting xkbcommon off the ground initially.