[whatwg] Processing the zoom level - MS extensions to window.screen

Ian Hickson ian at hixie.ch
Thu May 12 21:29:05 PDT 2011

On Fri, 13 May 2011, Glenn Maynard wrote:
> On Thu, May 12, 2011 at 11:34 PM, Ian Hickson <ian at hixie.ch> wrote:
> >
> > No, ImageData exposes the underlying data, not the data in CSS pixels.
> I know.  That's what I was responding to: having different backing store 
> dimensions and dimensions exposed by ImageData doesn't make sense.
> If you mean that getImageData might return data of different dimensions 
> than the canvas coordinate space (which I see the spec allows), that 
> sounds like it would cause major interop problems if anyone actually did 
> that.  It's very unobvious and I'd expect most people to miss it.

It's pretty much the entire point of that API. That's why it has separate 
height/width information than the canvas. It has to be that way because 
there's no guarantee that CSS pixels will map to device pixels -- and 
that's not theoretical, there are shipping devices with high-density 
screens already (e.g. the iPhone).

> Anyway, this doesn't help this case in general anyway because the 
> full-screen zoom level can change at any time.

Sure, but there's not much that can be done for that case.

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

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