Question about XRender specification

Clemens Eisserer linuxhippy at
Tue Apr 8 15:15:40 PDT 2008


Thanks a lot for all the help and suggestions.

> No. The XRenderCompositeTrapezoids call pre-composes the trapezoids
>  together into a single mask, (with ADD I believe), and the uses that
>  as the mask for the Over operation being asked for here.
Ah, good to know - this saves some work :)

> That 0 there is odd, and I assume it must be a bug.
>  I've attached my working program below. It uses an A8 format for the
>  maskFormat and I get seamless rendering with antialiasing on the outer
>  edges. If I use 0 there, I still get seamless rendering, but
>  non-antialiased outer edges, (which is what I would expect for an A1
>  format, so maybe that is what the 0 is being interpreted as).
>  Clemens, is there something very different in your test case compared
>  to mine?
The missing maskFormat was the problem - with your A8 format
everything works as expected.
Thanks a lot for the whole investigation and for even writing code to test :)

I am not sure if I understand that parameter correctly, does it
specify the depth of the intermediate mask which is generated for

Thank you very much, lg Clemens

>  PS. Ouch, it sure is painful to write programs that draw with Xrender
>  directly. I'm glad that I've got cairo to take care of these details
>  for me.
Well, from another POV its quite interesting to learn whats behind Cairo ;)

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