[cairo] Clipping and on-demand redraw

[Lawrence D'Oliveiro]

On Sat, 9 Jan 2016 23:11:44 +0100, Enrico Weigelt, metux IT consult
wrote:

> But I dont know yet, how to do that also w/ rotation.

You can convert the bounding rectangle of the widget to a clip path, and
do path intersection/subtraction etc.

Or you could simplify it, and compute a bigger axis-aligned bounding
rectangle for a rotated widget. Then you only need to do operations
on axis-aligned rectangles.