[cairo] Fix for get-path-extents test cases

Chris Wilson chris at chris-wilson.co.uk
Thu Jun 20 00:39:03 PDT 2013

On Wed, Jun 19, 2013 at 10:51:34PM +0000, Bryce W. Harrington wrote:
> Chris,
> I ran across bug 62375 about the get-path-extents test case breakage.  You posted a patch there a few months back, to switch from _cairo_path_fixed_stroke_polygon_to_traps() to just _cairo_path_fixed_stroke_to_polygon(), which makes a couple dozen tests pass (below) and none fail.  The former appears to be running _cairo_bentley_ottmann_tessellate_polygon over the polygon and I gather this was what breaks the test.  Unfortunately the output files for this test seem to be empty when it passes, so I'm not sure what's happening here.
> Could you elaborate on your thoughts regarding that patch?  Is it just a workaround, or would it be suitable as a fix?

Avoiding the intermediate traps for determining tesselated extents is
the right approach. The other question though is whether the error for
the traps path is less than tolerance - the test should be fixed not to
expect answers to higher precision than tolerance and should also test
with varying tolerance. It would be worth checking that first.

Chris Wilson, Intel Open Source Technology Centre

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