By default, routines that draw to a drawing surface use a colour matching
algorithm that selects an optimum colour match corresponding to the supplied
colour value. Colour matching can be switched off (for all drawing surfaces) by
calling this routine with the argument set to zero. A non-zero value switches
If automatic colour matching is switched off, a matched colour can still be
obtained from GET_MATCHED_COLOURS@. The result is used as an RGB value in any
of the drawing surface routines.
Using this routine may lead to a significant improvement in the performance of
your program since colour matching is often unnecessary. When colour matching
is desirable, it is only necessary to apply the matching algorithm once for
each colour that is used.