guido@cwi.nl (Guido van Rossum) (03/27/91)
I have a library of graphics functions that I want to port to use GL on the 4D/45 for rendering. My library draws monochrome images only, and allows an XOR drawing mode. This is used for user interface features. I have studied the GL manual extensively, but cannot seem to find a way of doing this without reading a rectangle of pixels, doing the operation myself, and writing the rectangle back; this is not only slow but also requires a lot of work if I want to render XOR lines. I know it can be done, because the X server supports XOR drawing. (I have the feeling that it may be difficult though, because earlier versions of the X server had a clipping bug for XOR drawing...) Changing the applications is out of the question, and so is using X (in fact I already have a version that uses X, but I'd like to have one that uses GL as well). --Guido van Rossum, CWI, Amsterdam <guido@cwi.nl> The home of STDWIN
guido@cwi.nl (Guido van Rossum) (03/27/91)
Ok, I've done it again. Found the answer with the help of a close colleague (not quite a roommate but still). XOR drawing in GL is done with 'logicop(LO_XOR)'. Doesn't work on all hardware, but does on mine, so I'm happy. --Guido van Rossum, CWI, Amsterdam <guido@cwi.nl> "It's probably pining for the fiords"