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

[cu]

You are correct - I re-ran a few performance measurements, and there is
no perceptible difference between "source" and "over" when using
Pixman/image backend.

I was confusing it with Quartz backend where we found about a 2x time
difference (it appears that Quartz is going through image backend when
painting from one surface to another, though honestly I didn't
investigate in-depth)

Thank you for the fix, will apply shortly.

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