| |||||||||||||
X: 25 years and still lacking vsync'ed double bufferingX: 25 years and still lacking vsync'ed double bufferingPosted Oct 7, 2009 4:47 UTC (Wed) by pphaneuf (guest, #23480)In reply to: X: 25 years and still lacking vsync'ed double buffering by dion Parent article: LPC: 25 years of X
I think the reason why there's no good vsync support in X is that you can't hook interrupts from user-space, and they didn't want to poll, because it would have made everything else suck. Note that there's nothing in the X11 API that precludes using vsync to avoid tearing without exposing it in the API. What you need is just for a drawing command not to be in effect while the retrace is over the affected area. X could implement its drawing so that this doesn't happen in the middle of one of its drawing commands, and you wouldn't get tearing. Now, you might not want a partially drawn image, even if it does so without any tearing. In that case, you can just do the double buffering yourself, by drawing into a pixmap instead of directly in the window, and XCopyArea the pixmap to the window when you're done (which is a single operation, so could be done without tearing). The only thing that would need an extension for is throttling, so that you don't draw more than one image to your pixmap when only one copy can be made to the window. What you'd want is a XCopyArea that would send an event back to the client when it has been done. That can even support two displays with different update rates, you'd just get the event for different copies at a different rate, depending on where you put it.
(Log in to post comments)
|
|||||||||||||