65 lines
2.4 KiB
Markdown
65 lines
2.4 KiB
Markdown
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# Compatibility {#xkbcommon-compatibility}
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@tableofcontents{html:2}
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## XKB support {#xkb-v1-compatibility}
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Relative to the XKB 1.0 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 @anchor geometry
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@anchor 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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@anchor KcCGST-support
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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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- key behaviors
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+ used to implement radio groups and overlays, and to deal with things
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like keys that physically lock; 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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On the other hand, some features and extensions were added.
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### Notable additions
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- 32-bit keycodes
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- extended number of modifiers (planned)
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- extended number of groups (planned)
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- multiple keysyms per level
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+ such levels are ignored by x11/xkbcomp.
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- key names (e.g. `<AE11>`) can be longer than 4 characters.
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## Compose support {#compose-support}
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Relative to the standard implementation in libX11 (described in the
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Compose(5) man-page), some features are not supported:
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- the (! MODIFIER) syntax
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+ parsed correctly but ignored.
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- using modifier keysyms in Compose sequences
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- several interactions with Braille keysyms
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