[Haskell-cafe] Re: Why binding to existing widget toolkits doesn't make any sense

Duncan Coutts duncan.coutts at worc.ox.ac.uk
Sat Jan 31 14:54:57 EST 2009

On Sat, 2009-01-31 at 13:18 +0100, Peter Verswyvelen wrote:
> When I said Cairo felt rather slow, I was comparing it again fully
> hardware accelerated solutions. 
> With Cairo I am unable to perform full smooth screen redraws of even
> just a single solid rectangle, and when you are making ZUI (zoomable
> user interfaces), full screen redraws are not uncommon. "Smooth" here
> means at least 30 frames per second, but preferably 60 frames per
> second. It seems not the number of shapes that are rendered is the
> bottleneck, but the amount of pixels covered. At least that is what I
> noticed. I guess this is because it is a 100% software renderer, and
> it might have to perform per pixel conversion when copying to the
> video card, but I really don't know.

The X11 backend is accelerated if your X server supports it. It uses the
XRender extension. If you draw to an image surface then yes that is
software rendering. If you're happy to be connected to the X server then
you can still do off-screen drawing and again if your X server supports
it that can be accelerated too.

Some X servers accelerate some XRender operations and not others. I
think some of the gradient fills are problematic.


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