I was being dense, making one, then calling grabpixmap as well. That would ahve been a memory hole before auto GC. Thanks.
However, I guess the question about finding out the backbuffer format is still valid in the event you wanted to create a pixmap and copy portions of the backbuffer to it with readpixel and writepixel...
However, I guess the question about finding out the backbuffer format is still valid in the event you wanted to create a pixmap and copy portions of the backbuffer to it with readpixel and writepixel...