Set the current fill rule within the Cairo context. The fill rule
is used to determine which regions are inside or outside a complex
(potentially self-intersecting) path. The current fill rule affects
both ccontext:Fill() and ccontext:Clip(). The following
values can be passed for fill_rule:
#CAIRO_FILL_RULE_WINDING-
If the path crosses the ray from left-to-right, counts +1. If the path
crosses the ray from right to left, counts -1. Left and right are determined
from the perspective of looking along the ray from the starting point. If
the total count is non-zero, the point will be filled.
#CAIRO_FILL_RULE_EVEN_ODD-
Counts the total number of intersections, without regard to the orientation
of the contour. If the total number of intersections is odd, the point will
be filled.
The default fill rule is #CAIRO_FILL_RULE_WINDING.