[cairo-bugs] [Bug 26024] New: Unbound compositing of gradients might fail

[bugzilla-daemon at freedesktop.org]

http://bugs.freedesktop.org/show_bug.cgi?id=26024

           Summary: Unbound compositing of gradients might fail
           Product: cairo
           Version: 1.9.5
          Platform: All
        OS/Version: All
            Status: NEW
          Severity: major
          Priority: medium
         Component: image backend
        AssignedTo: cworth at cworth.org
        ReportedBy: ranma42 at gmail.com
         QAContact: cairo-bugs at cairographics.org


Compositing a gradient using an unbound operator will often fail in the
fallback path (thus at the very least in image), as shown by
radial-gradient-source.

I've been able to track down the source of this problem to a bad interaction
between pixman having gradients as 0x0 images and the fallback fixup for
unbound operation, which uses the size of the images to compute the area of the
dest image to be cleared (see _cairo_surface_composite_fixup_unbounded in
cairo-surface.c). This only happens when the composited source has EXTEND_NONE
as otherwise the source is always considered to be infinite (is this correct
even when the image really is 0x0?)
Image passes radial-gradient-source in wip/compositor (where the old fallback
path has been removed).

Maybe this should be a blocker for 1.10, even if it's not a regression, afaict

(I know that this testsuite failure is available to all the developers, but I
wanted to keep track of the observations I made by debugging and inspecting the
code, since I have no patch for this bug, yet)


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