[whatwg] High-density canvases

[Dean Jackson]

On 11 Sep 2013, at 3:20 am, Robert O'Callahan <robert at ocallahan.org> wrote:

> On Tue, Sep 10, 2013 at 1:26 PM, Rik Cabanier <cabanier at gmail.com> wrote:
> There's a thread on www-style:
> http://lists.w3.org/Archives/Public/www-style/2012Nov/0144.html
> It's been in firefox for a while and blink is going to ship it soon:
> https://groups.google.com/a/chromium.org/forum/#!topic/blink-dev/RyUSi3zdumQ
> 
> devicePixelRatio has reflected page zoom in Firefox ever since we first exposed it (because the thing it maps to internally has always been affected by page zoom).

OK. I can accept that it makes sense for page zoom (I was only thinking about pinch zoom... which is a bad name). Still, we've (Apple) been telling developers for a long time that devicePixelRatio is (basically) constant. I guess we'll have to either change or be non-conformant.

>  
> > > Actually what I really think we should do is also change the
> > > window.devicePixelRatio for pinch zoom. Combined with the suggestions for
> > > canvas, that would allow (as Rik pointed out on IRC) for high-quality
> > > canvas all the way zoomed in, and for cheap canvases when zoomed out
> 
> I believe pinch zoom should not change devicePixelRatio. It would be nice
> if there was a standard way to determine pinch zoom though and if the
> canvas could automatically resize.
> 
> Pinch-zoom is hard because we don't want to trigger reflows or other expensive behavior on pinch-zoom. I'd leave pinch-zoom out of it for now.

Agreed.

Dean