Does clipRect parameter of the BitmapData.draw method really clips the source?

Answer 1

I never had any glitches with draw() and its clip rect. It is by the way implemented very well and gives you an important performance boost if done correct. The Flash rasterizer will only draw the parts of the clipRect.

Regarding your code: I would actually try it with and without the matrix. This could be the problem. You translate and clip. Basically clipping should happen before translation but I am not quite sure about that one.

Answer 2

I had the same problem as you. Upon coming across your post. I tried what you said. Treating the cliprect is actually clipping the target instead of the source. My program works as intended immediately. So yes, in a way it does seems that the cliprect is for clipping the target instead of the source.