- From: James Robinson <jamesr@google.com>
- Date: Tue, 13 Nov 2012 22:42:12 -0800
- To: "Tab Atkins Jr." <jackalmage@gmail.com>
- Cc: Simon Fraser <smfr@me.com>, www-style list <www-style@w3.org>, "L. David Baron" <dbaron@dbaron.org>, "Robert O'Callahan" <robert@ocallahan.org>
- Message-ID: <CAD73mdJ-cqrZRN7gArN6wiRUa=Oq6Rkv+KQhszyC+070t9PPxQ@mail.gmail.com>
On Nov 13, 2012 8:09 PM, "Tab Atkins Jr." <jackalmage@gmail.com> wrote: > > On Tue, Nov 13, 2012 at 6:02 PM, James Robinson <jamesr@google.com> wrote: > > On Tue, Nov 13, 2012 at 5:21 PM, Tab Atkins Jr. <jackalmage@gmail.com> > > wrote: > >> As far as I can tell, we do the wrong thing. When I Ctrl-+ my way to > >> maximum "zoom" (really "rescale", I think) on my desktop (such that > >> <body> reports its width as being 272px wide instead of 1424px), > >> window.dPR still returns 1. > > > > That's a completely different type of 'zoom' from what happens on mobile. > > Ctrl+ in Chrome is 'Page Zoom' using the terminology here: > > http://trac.webkit.org/wiki/ScalesAndZooms. Pinch zooming on a mobile > > device in WebKit is 'Page Scale' using that terminology. Neither change > > window.devicePixelRatio - that's an artifact of the display and cannot be > > changed by user interaction. > > Yes, that's what we're saying - the "zoom" operation from mobile > browsers, where zooming and panning the virtual viewport is common, > should be considered distinct from the "zoom" operation done by > desktop browsers, where you're actually changing the number of pixels > that fit into the viewport. I've been calling the latter operation > "rescale" rather than "zoom" just to help distinguish. When I Ctrl-+ > in desktop Chrome, the ICB is actually made smaller (in px), which is > very different than scaling up the virtual viewport on mobile Chrome. > > When I Ctrl-+ a lot, then ask <body> (which is filling the screen) > what its size is, it reports a number less than 1/5 what it "should" > report. That means we're actually, for the purpose of every useful > metric, rescaling the CSS px relative to the device pixel, and > window.dPR should reflect that. Otherwise, you get nonsensical > results. That doesn't follow for me - devicePixelRatio is a physical property of the display which unless your laptop is a lot cooler than mine doesn't change when you press Ctrl-+. - James > > ~TJ
Received on Wednesday, 14 November 2012 06:42:40 UTC