Hi Cairo developers, and thank you for a very good and easy-to-use library. I have a bunch of polygons that the user can click on. Now I want to "disable" some of them, and I want to indicate this by making them darker. The easiest way seems to be to draw a dark semi-transparent gray rectangle over everything else, and mask out the enabled polygons. But I cant figure out how to do the masking (how to cut holes in the rectangle). It seems I cant use a pattern for masking here, so that leaves me with having to create a new surface the size of the original surface, and use that as the mask. I havent tried this, but wouldnt it waste a lot of memory? I'm uncomfortable with duplicating everything, but then again I dont really know what a surface is inside of Cairo, so maybe I'm imagining problems here. Can you help me? How would you solve my problem? Thanks in advance.