[cairo] Cairo Fill Rule - Alternate

[Uli Schlachter]

Hi,

On 22.10.2012 12:57, Adhir Garg wrote:
> This is about CAIRO fill rule.
> Currently we have 2 rules for filling in cairo. From the manual
> http://www.cairographics.org/manual/cairo-cairo-t.html#CAIRO-FILL-RULE-WINDING:CAPS
> (1) CAIRO_FILL_RULE_WINDING
> (2) 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. (Since 1.0)
> 
> We don't have the way to "fill" in using the ALTERNATE rules i.e. if
> we have Triangle (Polygon of length 3) inside Rectangle (Polygon of
> length 4) and we want to fill in the area between Rectangle and
> Triangle. From initial thoughts, EVEN_ODD was probably the same, but
> it revealed (being similar to SVG) that it fills depending on the
> intersections and not on the difference in sides of polygon.

I don't really get your problem (nor do I get what the difference between
"intersections" and "sides" would be). Could you elaborate?

If you want to draw the difference between a rectangle and a triangle, you can
do so with both fill rules. But more easily you can do so with the even-odd
rule. It should Just Work (tm). Do you have any (self contained) example code of
what you are trying to do that gets the wrong result?

Cheers,
Uli
-- 
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 - Vincent Ebert