[cairo] Rendering bug when using operator "source" (ver. 1.12)

[Chris Wilson]

On Wed, 28 Mar 2012 18:10:29 -0400, cu <cairouser at yahoo.com> wrote:
> Resolution would be greatly appreciated, as at this point we have to use
> operator "over" instead, resulting in un-needed overhead.

I should point out that the output is different between OVER and SOURCE
in this case. Along the partially filled top edge, using SOURCE the edge
is going to be blend with CLEAR (the operation is implicitly clearing
the destination before adding the source on top) whereas with OVER that
edge is blended by the inverse-coverage factor with the existing
content.

Ideally the only performance difference would be when applying the
antialiased edge - we're not quite there, but it should be fairly close.
-Chris

-- 
Chris Wilson, Intel Open Source Technology Centre