[cairo] Clip region problems
otaylor at redhat.com
Wed Apr 27 08:33:58 PDT 2005
On Fri, 2005-03-11 at 16:04 -0500, Owen Taylor wrote:
> * For exact rectangular clips, we change the clip region on the
> destination surface, but we don't necessarily reset it
> when we are done drawing to the surface.
> We also don't do anything to guard against the same surface
> being used as the target of two cairo_t, or the target of
> a cairo_t and a source for drawing to another cairo_t.
> * In libpixman and Render, a clip region set on a source affects
> rendering... clipped pixels are treated as fully transparent.
> This isn't particularly useful behavior, but because of the
> above problems, it will leak out and affect Cairo rendering
> in some cases.
> So, how do we fix these problems? Ideas:
> 4. Only allow a surface to be used for a single thing at a same time
> - two cairo_t's cannot be active for the same target surface
> - a surface that is the target of a cairo_t cannot be used
> as a source.
> Pro: Simple
> Con: Fairly big restriction
Would it be OK if I implemented this for now? Leaked clips are
biting me a lot in GTK+.
We can always relax the restriction later.
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