Xkb provides functions to add a single new element to the top-level keyboard geometry. In each case the
num_* fields of the corresponding structure is incremented by 1. These functions do not change sz_*
unless there is no more room in the array. Some of these functions fill in the values of the element's
structure from the arguments. For other functions, you must explicitly write code to fill the structure's
elements.
The top-level geometry description includes a list of geometryproperties. A geometry property
associates an arbitrary string with an equally arbitrary name. Programs that display images of keyboards
can use geometry properties as hints, but they are not interpreted by Xkb. No other geometry structures
refer to geometry properties.
An outline consists of an arbitrary number of points. XkbAddGeomOutline adds an outline to the specified
shape by reserving sz_points points for it. The new outline is allocated and zeroed. XkbAddGeomOutline
returns NULL if any of the parameters is empty or if it was not able to allocate space. To allocate space
for an arbitrary number of outlines to a shape, use XkbAllocGeomOutlines.