Xkb provides several functions that make it easier to apply the compatibility
map to configure a client-side Xkb keyboard mapping, given a core protocol
representation of part or all of a keyboard mapping. Obtain a core protocol
representation of a keyboard mapping from an actual server (by using
XGetKeyboardMapping, for example), a data file, or some other source.
XkbUpdateMapFromCore interprets input argument information representing a keyboard map in core format
to update the Xkb keyboard description passed in
xkb. Only a portion of the Xkb map is updated - the portion corresponding to keys
with keycodes in the range
first_key + num_keys - 1. If
XkbUpdateMapFromCore is being called in response to a MappingNotify event,
num_keys are reported in the MappingNotify event.
core_keysyms contains the keysyms corresponding to the keycode range being updated, in core
keyboard description order.
map_width is the number of keysyms per key in
core_keysyms. Thus, the first
map_width entries in
core_keysyms are for the key with keycode
first_key, the next
map_width entries are for key
first_key + 1, and so on.
In addition to modifying the Xkb keyboard mapping in
xkb, XkbUpdateMapFromCore backfills the changes structure whose address is passed in
changes to indicate the modifications that were made. You may then use
changes in subsequent calls such as
XkbSetMap, to propagate the local modifications to a server.