[cairo] Clip region problems
otaylor at redhat.com
Wed Apr 27 09:31:39 PDT 2005
On Wed, 2005-04-27 at 11:33 -0400, Owen Taylor wrote:
> > 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.
Thinking about this some more, I'm not totally happy with this
restriction ... it's going to cause code like:
cr = gdk_drawable_create_cairo_context (d);
/* ... draw with cairo ... */
gtk_paint_flat_box (widget, d, ...);
/* ... more drawing with cairo ... */
To fail. So perhaps a less restrictive version is to require creation
and use of cairo_t's for one cairo-surface to be nested. This can
be implemented with a simple stack of saved clip regions.
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