114 lines
4.7 KiB
Plaintext
114 lines
4.7 KiB
Plaintext
xkbcommon
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=========
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libxkbcommon is a keymap compiler and support library which processes a
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reduced subset of keymaps as defined by the XKB specification. Primarily,
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a keymap is created from a set of Rules/Model/Layout/Variant/Options names,
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processed through an XKB ruleset, and compiled into a struct xkb_desc, which
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is the base type for all xkbcommon operations.
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From an xkb_desc, an xkb_state object is created which holds the current
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state of all modifiers, groups, LEDs, etc, relating to that keymap. All
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key events must be fed into the xkb_state object using xkb_state_update_key.
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Once this is done, the xkb_state object will be properly updated, and the
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keysyms to use can be obtained with xkb_key_get_syms.
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libxkbcommon does not distribute a dataset itself, other than for testing
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purposes. The most common dataset is xkeyboard-config, as used by all
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current distributions for their X11 XKB data. More information on
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xkeyboard-config is available here:
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http://www.freedesktop.org/wiki/Software/XKeyboardConfig
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API
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===
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While xkbcommon's API is somewhat derived from the classic XKB API as found
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in <X11/extensions/XKB.h> and friends, it has been substantially reworked to
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expose fewer internal details to clients. The only supported API is available
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in <xkbcommon/xkbcommon.h>. Any definition not in this header (including
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accessing internal structures through the old macros previously available)
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should be regarded as an implementation detail and is liable to change at any
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time.
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During its early development, xkbcommon does not promise API or ABI stability.
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Regardless, we will attempt to not break ABI during a minor release series,
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so applications written against 0.1.0 should be completely compatible with
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0.1.3, but not necessarily with 0.2.0. However, new symbols may be introduced
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in any release. Thus, anyone packaging xkbcommon should make sure any package
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depending on it depends on a release greater than or equal to the version it
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was built against (or earlier, if it doesn't use any newly-introduced
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symbols), but less than the next major release.
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xkbcommon 1.x will offer full API and ABI stability for its lifetime, with a
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soname of libxkbcommon.so.1. Any ABI breaks will wait until xkbcommon 2.0,
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which will be libxkbcommon.so.2.
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The xkbcomp command-line tool has also been removed, although this will
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likely reappear in a later release.
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Relation to X11
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===============
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Relative to the XKB 1.1 specification implemented in current X servers,
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xkbcommon has removed support for some parts of the specification which
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introduced unnecessary complications. Many of these removals were in fact
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not implemented, or half-implemented at best, as well as being totally
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unused in the standard dataset.
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Notable removals:
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- geometry support
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+ there were very few geometry definitions available, and while
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xkbcommon was responsible for parsing this insanely complex format,
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it never actually did anything with it
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+ hopefully someone will develop a companion library which supports
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keyboard geometries in a more useful format
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- KcCGST (keycodes/compat/geometry/symbols/types) API
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+ use RMLVO instead; KcCGST is now an implementation detail
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+ including pre-defined keymap files
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- XKM support
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+ may come in an optional X11 support/compatibility library
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- around half of the interpret actions
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+ pointer device, message and redirect actions in particular
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- non-virtual modifiers
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+ core and virtual modifiers have been collapsed into the same
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namespace, with a 'significant' flag that largely parallels the
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core/virtual split
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- radio groups
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+ completely unused in current keymaps, never fully implemented
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- overlays
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+ almost completely unused in current keymaps
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- indicator behaviours such as LED-controls-key
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+ the only supported LED behaviour is key-controls-LED; again this
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was never really used in current keymaps
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Notable additions:
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- 32-bit keycodes
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- extended number of modifiers
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- extended number of groups
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- multiple keysyms per level
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+ this requires incompatible dataset changes, such that X11 would
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not be able to parse these
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Development
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===========
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xkbcommon is maintained in git at freedesktop.org:
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git://anongit.freedesktop.org/git/xorg/lib/libxkbcommon
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Patches are always welcome, and may be sent to either xorg-devel@lists.x.org,
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or wayland-devel@lists.freedesktop.org. Bugs are tracked in Bugzilla at:
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http://bugs.freedesktop.org
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The primary author and maintainer is Daniel Stone, who can be reached at:
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<daniel@fooishbar.org>
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Credits
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=======
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Many thanks are due to Dan Nicholson for his heroic work in getting xkbcommon
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off the ground initially, as well as to Ran Benita for subsequent development.
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