On Thu, Feb 14, 2013 at 3:21 AM, Benjamin Smedberg <benja...@smedbergs.us>wrote:
> On what OSes? Windows by default coalesces mouse move events. They are > like WM_PAINT events in that they are only delivered when the event queue > is empty. See > http://blogs.msdn.com/b/oldnewthing/archive/2011/12/19/10249000.aspx > > This should basically mean that we process mousemove events on windows up > to 100% CPU, but we should never be "flooded" by them. Although I do wonder > if WM_MOUSEMOVE has priority over WM_PAINT so that if the mouse is moving a > lot, that could affect the latency of WM_PAINT. > We are definitely getting flooded. Here's what I think is happening on the page I'm looking at, it's pretty simple: 1) nsAppShell::ProcessNextNativeEvent checks for input events, finds a WM_MOUSE_MOVE, and dispatches it, which takes a little while because this page's mousemove handler modifies and flushes layout on every mouse move. 2) While that's happening, the mouse keeps moving. 3) After processing that WM_MOUSE_MOVE, ProcessNextNativeEvent calls PeekMessage again and finds another WM_MOUSE_MOVE is ready. Go to step 1. 4) Meanwhile the refresh driver timer has fired and queued an event, but we don't get around to running it until NATIVE_EVENT_STARVATION_LIMIT has expired (one second). I suppose we could try ignoring WM_MOUSE_MOVEs when there's a Gecko event pending, but that sounds kinda scary. I think deferring DOM mousemove events to the next refresh driver tick would be safer than that. Rob -- Wrfhf pnyyrq gurz gbtrgure naq fnvq, “Lbh xabj gung gur ehyref bs gur Tragvyrf ybeq vg bire gurz, naq gurve uvtu bssvpvnyf rkrepvfr nhgubevgl bire gurz. Abg fb jvgu lbh. Vafgrnq, jubrire jnagf gb orpbzr terng nzbat lbh zhfg or lbhe freinag, naq jubrire jnagf gb or svefg zhfg or lbhe fynir — whfg nf gur Fba bs Zna qvq abg pbzr gb or freirq, ohg gb freir, naq gb tvir uvf yvsr nf n enafbz sbe znal.” [Znggurj 20:25-28] _______________________________________________ dev-platform mailing list dev-platform@lists.mozilla.org https://lists.mozilla.org/listinfo/dev-platform
