Is there any way that I can paint with or set a transparent color on my own Ctrl? For example, if I were to draw a playing card as a ctrl, and I wanted to round the borders slightly, it would be easier to "erase" the corners than to go out of my way to not try to paint the corners in the first place.
Not sure I quite understand, but I guess the straight reply is no.
The problem is that it is not known what is the correct background. If things are transparent, the only correct solution to get the right appearance is to paint things in z-order...