Xkb provides a number of functions to allocate and free subcomponents of a
keyboard geometry. Use these functions to create or modify keyboard geometries.
Note that these functions merely allocate space for the new element(s), and it
is up to you to fill in the values explicitly in your code. These allocation
sz_* but never touch
num_* (unless there is an allocation failure, in which case they reset both
num_* to zero). These functions return Success if they succeed, BadAlloc if they are
not able to allocate space, or BadValue if a parameter is not as expected.
num_needed doodads and adds them to the specified geometry
geom. No initialization of the doodads is done.