[cairo] Threading: painting from the same source_surface

[Arjen Nienhuis]

Hi,

I have a big png file that I try to copy to two different
ImageSurfaces using two different threads.

One of the two resulting images is corrupted.

Is this a bug in cairo or in my code (wrong assumptions about threading)?

Here is my pseudo-python-code:

Thread 1:
========
src = cairo.ImageSurface.create_from_png(path)
...
ctx = cairo.ImageSurface(...)
ctx.translate(...)
ctx.scale(...)
ctx.set_source_surface(src)
ctx.paint()

Thread 2:
========
ctx = cairo.ImageSurface(...)
ctx.translate(...)
ctx.scale(...)
ctx.set_source_surface(src)
ctx.paint()

The result from thread 1 is T1_bad.jpg but should be T1_ok.jpg. (What
happened to the text?)
Thread 2 is fine and results in T2.jpg.
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