[whatwg] Hardware accelerated canvas

[Benoit Jacob]

----- Original Message -----
> On Tue, Sep 4, 2012 at 10:15 AM, Boris Zbarsky <bzbarsky at mit.edu>
> wrote:
> > So now our list is:
> >
> > 1)  Have a way for pages to opt in to software rendering.
> > 2)  Opt canvases in to software rendering via some sort of
> > heuristic
> >     (e.g. software by default until there has been drawing to it
> >     for
> >     several event loop iterations, or whatever).
> > 3)  Have a way for pages to opt in to having snapshots taken.
> > 4)  Auto-snapshot based on some heuristics.
> > 5)  Save command stream.
> > 6)  Have a way for pages to explicitly snapshot a canvas.
> > 7)  Require opt in for hardware accelerated rendering.
> > 8)  Authors use toDataURL() when they want their data to stick
> > around.
> > 9)  Context lost event that lets authors regenerate the canvas.
> > 10) Do nothing, assume users will hit reload if their canvas goes
> > blank.
> 
> 11) Default to best-effort (current behavior), but allow opting in to
> getting notifications about lost context, in which case the browser
> would not need to do various tricks in order to attempt to save the
> current state.
> 
> I.e. basically 4, but with the ability for the page to opt in to 9.

Keep in mind that snapshotting as in 4 will cause a large memory usage increase for large canvases, and will cause animation choppiness on certain pages on systems where readback is expensive. So the heuristics have to be specified in a precise manner, or else browser vendors could well decide that the best heuristic is "never".

Benoit

> 
> It sounds like no browsers do any such tricks right now, so
> effectively the opt-in would be to just be notified. But possibly
> browsers might feel the need to do various snap-shot heuristics on
> mobile as they start to hardware accelerate there.
> 
> / Jonas
>