[cairo] filters/image processing

[Bill Spitzak]

I think there is FAR too much worry about making every implementation 
draw the same in cairo, and this is really blocking getting things done 
and accelerated.

What I (and I suspect most users of cairo) want is that all 
implementations "work" (in that there are no missing symbols and the 
program links) and that *something* is drawn that is approximately the 
same shape and color as the correct result, so you can tell exactly what 
portion of cairo is being mis-implemented.

In this case of GLSL, my recommendation is a new interface to set the 
compositing to "use this GLSL, and if you don't support it, use this 
compositing operation". There is zero interest in getting GLSL or any 
filtering to work on unaccelerated backends, but being able to say if 
your operation is similar to over or add or clear is probably useful for 
making the output more legible when the OpenGL backend is not there.

MenTaLguY wrote:

> What about the X and image surfaces, though?  The motivating problem was
> to write an SVG renderer that supported SVG filter effects atop cairo,
> for which glitz is not always an option, any more than GLSL will be
> ubiquitous in deployed hardware for quite some time.