[whatwg] High-density canvases

Dean Jackson dino at apple.com
Tue Sep 10 12:45:13 PDT 2013

On 11 Sep 2013, at 5:32 am, Ian Hickson <ian at hixie.ch> wrote:

> On Wed, 11 Sep 2013, Dean Jackson wrote:
>> On 11 Sep 2013, at 12:14 am, Stephen White <senorblanco at chromium.org> 
>> wrote:
>>> now that some browsers are including browser zoom (page zoom) in 
>>> window.devicePixelRatio
>> Ouch. Who is doing this and why?
> Why ouch?

Because we’ve always operated under the assumption that devicePixelRatio is the mapping from CSS px to device pixels at 1:1 scale/zoom, and that it is constant for a particular display. The only change content would see is if the window is dragged to/from a high resolution screen.

There are other ways to query the page zoom.

I fear this will break existing content. I don’t think we’d ever want to change the behaviour.


> 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.

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