[cairo-bugs] [Bug 3018] Strange results from tesellating a rectangle

bugzilla-daemon at freedesktop.org bugzilla-daemon at freedesktop.org
Sun Sep 28 12:42:10 PDT 2008


--- Comment #2 from Chris Wilson <chris at chris-wilson.co.uk>  2008-09-28 12:42:04 PST ---
This is inherent to the tessellation stategy of
_cairo_tessellate_convex_quad(). This overhead is now avoided entirely for
single simple rectangles (with a special case tessellator). Empty traps are
currently skipped when extracting regions, so extra work is being done and
empty trapezoids are being rendered in the cases where the entire path can be
represented as a region. However we know the form of the empty trapezoids that
are most likely to be generated by our tessellators and so we can simply
discard them just before appending them to the array.

The oddity is that adding this early check generates subtly different results,
for instance the 'elbows' of dash-curve. Argubably its an improvement, but at
any rate this discrepancy looks like a bug in pixman.

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