creating non-rectangular clips

Hi folks,


for my widget toolkit (*1), I'm looking for a way to do non-rectangular
clipping. The purpose is to clip-out parts of an widget that are
covered by another one, so I dont need to repaint the overlapping
ones when repainting a single widget.

Each widget is defined by its origin point, size and angle (within
the parent's coordinate system). The rendering is done into patterns,
which are then composited within the parent window.

My idea now is going through all neighboring windows and create a clip
that masks out all the overlapping areas.

How could that be done ?


--mtx

*1) https://github.com/metux/twtk
--
Enrico Weigelt,
metux IT consulting
+49-151-27565287
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