To have a properly working key input in the xcb plugin in the case when
xcb-xkb library is not available we can update the xkb_state struct with the
keyboard state information available in the X11 core events.
The current modifier state is reported to clients in a number of core
protocol events and can be determined using the QueryPointer request.
This is how it is done in Weston, Wayland's reference implementation.
Note: In case the X server doesn't have a xkb support on it (which is very
unlikely), then xkbcommon will only pick up the user's primary layout.
The X server with the xkb support stuffs unused bits (13 and 14) of 'state' in the
core events with the effective keyboard group, which we can use to determine layout
changes.
Change-Id: I9f1ef635109870e7412ef1157ca592f3c8f9271c
Reviewed-by: Samuel Rødal <samuel.rodal@digia.com>
43578e1901