Comment 7 for bug 242990

My understanding of this is that it can't reasonably be done at an X level, although X provides the ability for apps to sync-to-vblank.

As I understand it, the problem with getting X to do this is that it'd have to check/sync for every drawing operation, making all drawing substantially slower. For some things (XVideo, for example) this can work, because the way Xv is used tends to be "draw this whole frame", so the overhead isn't bad. Regular drawing involves many, many operations to draw a single window, so the overhead becomes significant.

Now that compositing window managers are becoming widespread, this should be fixable. Composite allows you to do all the drawing offscreen, then the compositor draws the whole desktop to the screen in a single action, which can reasonably be synchronised with vblank. Compiz allows this.