On Wed, Aug 14, 2013 at 12:13 PM, Bas Schouten <bschou...@mozilla.com>wrote:
> Since you want composition to occur whenever drawing has occurred, I don't > really think it should really be what's working on doing any processing for > the vblank event. The VBlank event should just fire, indiscriminately > whenever VBlank occurs. I believe we should then consume that event on > whatever thread is actually doing drawing which might want to know about > this (a user input thread? the main thread?) and these should then decide > when to do their drawing and if that warrants a new composition. That way > you could have, just after vblank, all your scheduled drawing be done, and > a composition scheduled. But then if right before the next vblank a > panning/zooming event comes in you can still process that and present a new > frame to minimize latency (if desired). > That would be good in some ways, but it doesn't handle off-main-thread animation when the main thread's drawing is late (e.g. because the main thread is stuck doing something else). For that we must have a way to control composition based on VBlank signals that doesn't involve the main thread. > What you could also do is do all your main thread drawing and processing > rAF things just after vblank, since they'll likely be somewhat time > consuming, and schedule your composition only for example 5 ms before > VBlank (since that will likely be fast). You could then make some > adjustments to the layer tree through the APZC for user input later in the > frame, and still have those taken into account for composition, that would > give you a minimal input latency without wasted work and still starting the > content drawing required as early as possible giving it maximum opportunity > to make the next frame. This may be a little bit too complicated for a > first implementation, but I wanted to throw it out there as a suggestion as > well. > That sounds exactly like the "Lowering Latency" extension in the wiki page (if we treat everything as a "low latency" window). If you agree, maybe we should just do this. Rob -- Jtehsauts tshaei dS,o n" Wohfy Mdaon yhoaus eanuttehrotraiitny eovni le atrhtohu gthot sf oirng iyvoeu rs ihnesa.r"t sS?o Whhei csha iids teoa stiheer :p atroa lsyazye,d 'mYaonu,r "sGients uapr,e tfaokreg iyvoeunr, 'm aotr atnod sgaoy ,h o'mGee.t" uTph eann dt hwea lmka'n? gBoutt uIp waanndt wyeonut thoo mken.o w * * _______________________________________________ dev-platform mailing list dev-platform@lists.mozilla.org https://lists.mozilla.org/listinfo/dev-platform
