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
geometry properties. 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.

typedef struct _XkbOutline {
unsigned short num_points; /* number of points in the outline */
unsigned short sz_points; /* size of the points array */
unsigned short corner_radius; /* draw corners as circles with this radius */
XkbPointPtr points; /* array of points defining the outline */
} XkbOutlineRec, *XkbOutlinePtr;