late expose events may corrupt display #14
Description
It is possible that an expose event and a draw call get reordered so that the expose ends up drawing on top of the already drawn display. One blunt solution would be to always clear on expose (research this). Alternatively, we could force processing of exposes before any draw, but this doesn't seem complete or efficient. It's also quite possible this doesn't hurt anything anyway, since it should draw the same thing. The exception being the cursor, and I suspect this may be causing a cursor-wrong-on-attach bug, but I'm not sure.