To reproduce: 1. Go to http://neography.com/experiment/circles/solarsystem/ 2. Click and hold on the window's title bar The CSS animations pause for half a second, then continue. This does not happen in WebKit1.
<rdar://problem/9242727>
It looks like the entire main thread pauses when clicking and holding on the title bar. For example, DHTML animations stop, Safari's tabs' spinning progress indicators stop, etc. The only reason CSS animations don't pause in WebKit1 is that the animations are proceeding off the main thread. So really this bug boils down to "CSS animations happen on the main thread in WebKit2".
If you right-click instead of left-click, the animations will pause as long as you hold down the mouse button. See <http://us.generation-nt.com/answer/how-prevent-caption-bar-blocking-message-loop-help-13221142.html>.
(In reply to comment #2) > It looks like the entire main thread pauses when clicking and holding on the title bar. For example, DHTML animations stop, Safari's tabs' spinning progress indicators stop, etc. The only reason CSS animations don't pause in WebKit1 is that the animations are proceeding off the main thread. > > So really this bug boils down to "CSS animations happen on the main thread in WebKit2". So then is this Not To Be Fixed, or duped?
I do think we want to fix it. We'll just have to fix it by moving CSS animations off the main thread. Note that this could be done even while we're still reading bits back off the GPU into system memory. It's just a simple matter of writing code. :-) I don't think we have a general "CSS animations should happen on a background thread in WebKit2" bug. Maybe this bug could serve as it, or maybe filing a new one (and duping this one to that) would be clearer.
*** This bug has been marked as a duplicate of bug 58052 ***