Xfwm4 compositor zooming patch

Alistair Buxton a.j.buxton at gmail.com
Tue Nov 12 12:22:13 CET 2013


I have been working on implementing a zoom mode like compiz ezoom in Xfwm4.

You can find the current version at:


Press ALT and scroll up to zoom in.

The changes are relatively simple - it just applies a transformation
and filter to the final XRender call which copies the composed buffer
to the display. There should be negligible overhead if the display
isn't zoomed. So far I have one report that it works and one report
that it doesn't.

While I was doing this I found something strange:

The compositor sets the clipping region on rootPicture long before any
drawing happens on it. Is this a mistake? Was it supposed to set the
clipping on rootBuffer? The next block of drawing operations are all
done there. Or is there something more subtle to this code?
rootPicture is only drawn in to at the very end when the final
composed buffer is copied to it, so I think it would make more sense
to set the clipping region just before that is done, if that was the

Alistair Buxton
a.j.buxton at gmail.com

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