FM / compat

/usr/share/X11/xkb/compat

Name	Size	Mode	Actions
accessx	1121	0644	edit dl rm
basic	996	0644	edit dl rm
caps	507	0644	edit dl rm
complete	228	0644	edit dl rm
iso9995	1492	0644	edit dl rm
japan	979	0644	edit dl rm
ledcaps	469	0644	edit dl rm
ledcompose	287	0644	edit dl rm
lednum	466	0644	edit dl rm
ledscroll	486	0644	edit dl rm
level5	1273	0644	edit dl rm
misc	3053	0644	edit dl rm
mousekeys	4578	0644	edit dl rm
olpc	1001	0644	edit dl rm
pc	341	0644	edit dl rm
pc98	1094	0644	edit dl rm
README	1712	0644	edit dl rm
xfree86	1842	0644	edit dl rm
xtest	1399	0644	edit dl rm

Edit: /usr/share/X11/xkb/compat/README (1712B)

The core protocol interpretation of keyboard modifiers does not include direct
support for multiple keyboard groups, so XKB reports the effective keyboard
group to XKB-aware clients using some of the reserved bits in the state field
of some core protocol events. This modified state field would not be interpreted
correctly by XKB-unaware clients, so XKB provides a group compatibility mapping
which remaps the keyboard group into a core modifier mask that has similar
effects, when possible.

XKB maintains three compatibility state components that are used to make
XKB-unaware clients(*) work as well as possible:
- The compatibility state which corresponds to the effective modifier and
  effective group state.
- The compatibility lookup state which is the core-protocol equivalent of the
  lookup state.
- The compatibility grab state which is the nearest core-protocol equivalent
  of the grab state.

Compatibility states are essentially the corresponding XKB states, but with
the keyboard group possibly encoded as one or more modifiers.

Modifiers that correspond to each keyboard group are described in this
group compatibility map.

----
(*) The implementation of XKB invisibly extends the X library to use the
keyboard extension if it is present. That means, clients that use library or
toolkit routines to interpret keyboard events automatically use all of XKB's
features; clients that directly interpret the state field of core-protocol
events or the keymap directly may be affected by some of the XKB differences.
Thus most clients can take all advantages without modification but it also
means that XKB state can be reported to clients that have not explicitly
requested the keyboard extension.

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