[whatwg] <canvas> and high-density displays

[Ian Hickson]

On Mon, 24 Sep 2012, Glenn Maynard wrote:
> On Mon, Sep 24, 2012 at 6:40 PM, Ian Hickson <ian at hixie.ch> wrote:
> > 
> > We could add an event that fires on ImageData (or even ArrayBuffer) 
> > that fires when the data is available. If we add it to ArrayBuffer 
> > it's something that could be used in other contexts, too.
> >
> > Is this something that people think we should do? If so, should we add 
> > it to TypedArray generically?
> 
> If it's done this way, a nonblocking function may be needed to request 
> that the event be fired, without the blocking side-effects of actually 
> performing a pixel read.  Otherwise, implementations that don't perform 
> the readback at all until it knows it's really needed (eg. that it can't 
> be done with an in-GPU blit) would simply never fire the event at all. 
> Passing in a callback probably makes more sense this way than having it 
> request that an event be fired.
> 
> That would also allow waiting for readability without knowing in advance 
> whether the event was already fired or not, which would be important eg. 
> if you just received the ArrayBuffer in a message. (An attribute could 
> do this as well, but that might be more prone to developer error.)

Indeed.

If this is something that people want to follow up on, I recommend 
suggesting it to the WebGL mailing list where Typed Array lives. I don't 
think it makes sense for us to do a version just for canvas.

-- 
Ian Hickson               U+1047E                )\._.,--....,'``.    fL
http://ln.hixie.ch/       U+263A                /,   _.. \   _\  ;`._ ,.
Things that are impossible just take longer.   `._.-(,_..'--(,_..'`-.;.'