Xkb provides a number of convenience functions to help use a keyboard geometry. These include functions to return the bounding box of a shape's top surface and to update the bounding box of a shape row or section.
A shape is made up of a number of outlines. Each outline is a polygon made up of a number of points. The bounding box of a shape is a rectangle that contains all the outlines of that shape.
A ShapeRec contains a BoundsRec that describes the bounds of the shape. If you add or delete an outline to or from a shape, the bounding box must be updated.
XkbComputeShapeBounds updates the BoundsRec contained in the shape by examining all the outlines of the shape and setting the BoundsRec to the minimum x and minimum y, and maximum x and maximum y values found in those outlines. XkbComputeShapeBounds returns False if shape is NULL or if there are no outlines for the shape; otherwise, it returns True.
If you add or delete a key to or from a row, or if you update the shape of one of the keys in that row, you may need to update the bounding box of that row. To update the bounding box of a row, use XkbComputeRowBounds.
typedef struct _XkbShape {
Atom name; /* shape's name */
unsigned short num_outlines; /* number of outlines for the shape */
unsigned short sz_outlines; /* size of the outlines array */
XkbOutlinePtr outlines; /* array of outlines for the shape */
XkbOutlinePtr approx; /* pointer into the array to the approximating outline */
XkbOutlinePtr primary; /* pointer into the array to the primary outline */
XkbBoundsRec bounds; /* bounding box for the shape; encompasses all outlines */
} XkbShapeRec, *XkbShapePtr;
typedef struct _XkbBounds {
short x1,y1; /* upper left corner of the bounds, in mm/10 */
short x2,y2; /* lower right corner of the bounds, in mm/10 */
} XkbBoundsRec, *XkbBoundsPtr;