[webkit-dev] Device and page scaling

[Kenneth Rohde Christiansen]

On Wed, May 30, 2012 at 10:00 PM, Adam Barth <abarth at webkit.org> wrote:
> On Wed, May 30, 2012 at 12:08 AM, Kenneth Rohde Christiansen
> <kenneth.christiansen at gmail.com> wrote:
>> I don't think we are doing that much differently.
>>
>> Desktop Safari is scaling directly in WebCore using the
>> pageScaleFactor whereas Qt like iOS scales outside of WebCore (using a
>> tiled backing store), resulting in the FrameView not being in UI
>> pixels.
>
> This doesn't match what Simon Fraser wrote.  He said that all
> FrameView sizes on iOS are in "UI" pixels.

OK then I got it wrong :-) I thought that was only the case for
Desktop Safari. Anyway, the difference shouldn't be that big and I
guess we could migrate Qt to do the same (I actually had a proof of
concept of that working at some point). Currently we are applying a
scale to our GraphicsContext (QPainter), so that everything is drawn
with a scale, where as Safari actually adds the scale inside WebCore
using the pageScaleFactor.

Of course that means that our FrameView has the size as it was at
scale 1.0 and we have to do adjustments to innerHeight etc.

What are the advantages of the Safari approach? I guess you could make
the drawing better in some cases and you avoid external mapping of
event positions, but are there additional advantages? Any
disadvantages?

Kenneth

> Adam