Support cairo Regions

[tuxor1337]

cairocffi does not yet support cairo Regions: http://cairographics.org/manual/cairo-Regions.html

Originally reported as:

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Support for cairo_region_t doesn't seem to be there (segfault)

The problem described here for pycairo doesn't seem to be resolved when using cairocffi: https://bugzilla.gnome.org/show_bug.cgi?id=667959

Just try (same with Python 3)

Python 2.7.5 (default, Aug 22 2013, 09:31:58) 
[GCC 4.8.1 20130603 (Red Hat 4.8.1-1)] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> from gi.repository import Gdk
>>> import cairocffi as cairo
>>> surface = cairo.ImageSurface(0,100,100)
>>> Gdk.cairo_region_create_from_surface(surface)
Segmentation fault (core dumped)

Would be great to have cairo_region_t support, e.g. for input_shape_combine_region.

[SimonSapin]

Hi. Three things are going on here:

• First, cairocffi does not support cairo_region_t and related functions. It’s not hard to add, just a bit tedious (as I want everything to be tested and documented.)

• PyGobject (that you’re using to access GTK) doesn’t support cairocffi. One way to fix this is Pycairo C API support #18, emulate Pycairo’s C API in cairocffi. This is quite fragile and I’d rather do the alternative: change PyGObject to support cairocffi explicitly: https://bugzilla.gnome.org/show_bug.cgi?id=707196

  In the meantime, you can work around this by converting cairocffi wrappers to pycairo before giving them to PyGObject.

• Finally, PyGObject does not support cairo_region_t, which is the bug you linked. This requires either a new pycairo release, (which is unlikely as the project is dead) or fixing the two points above.

[SimonSapin]

So this issue is about the first point of my previous message: cairo Regions in cairocffi. If someone is interested in doing this work, I’d be happy to provide guidance.