This routine is used to create internal drawing surfaces. For example, it
can be used to display part of a large bitmap. Areas of the buffer can be
copied into a %gr region (for example) using COPY_GRAPHICS_REGION@. If you make
extensive use of this function it is recommended that you delete unwanted
surfaces with a call to DELETE_GRAPHICS_REGION@.
HANDLE is an input value, chosen by the programmer, that must be unique. It is
used to identify the surface in calls to related functions. WIDTH,
HEIGHT specify the size in pixels of the region.
The colour mode for the surface will be determined by the default colour mode or
by the colour mode of the current %gr drawing surface.