[cairo] pixman crash from setting clip region on image
dmon at xs4all.nl
Sat May 8 08:14:42 PDT 2004
> -----Original Message-----
> From: cairo-bounces at cairographics.org
> [mailto:cairo-bounces at cairographics.org] On Behalf Of
> Vladimir Vukicevic
> Sent: zaterdag 8 mei 2004 10:59
> To: Carl Worth
> Cc: cairo at cairographics.org
> Subject: Re: [cairo] pixman crash from setting clip region on
> image surface(patch)
> Hi Carl,
> Carl Worth wrote:
> > On Wed, 05 May 2004 20:21:37 -0700, Vladimir Vukicevic wrote:
> >>The attached patch fixes this; just a patch to icimage.c to
> check if the
> >>region is not NULL before setting a new clipping region.
> > Thanks. This is committed.
> More problems on this front, but I'm not sure what the fix is. When
> pixman gets a clip region set via
> pixman_image_set_clip_region, it takes
> ownership of this region and later destroys it in
> pixman_image_destroyClip when the clip region is changed.
> However, cairo also keeps track of the clip region in
> gstate->clip.region, and calls pixman_region_destroy on it in
> _cairo_gstate_fini, among others. So, given that cairo
> creates a region
> in _cairo_gstate_clip, and then assigns it to gstate->clip.region and
> calls _cairo_surface_set_clip_region() (which in turn calls
> pixman_image_set_clip_region) using the same pointer, we end
> up with a
> double free in many places where pixman_region_destroy() is called in
> One solution is to always create a copy of the region before calling
> _cairo_surface_set_clip_region (or that this function creates a copy
> before calling the back end implementation); however, this would mean
> that all the back ends would have to agree to clean up that region if
> they don't use pixman_image_set_clip_region().
> Any thoughts on how to fix this?
Yes, I noticed some clipping bugs also, clipping under win32 is
unusable(unpredictable crashes), I guess the win32 api isn't as
forgiving as glibc. I thought it was (another) problem with cairo on
win32, glad someone found out there's a bug.
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