1518908 - Make sure that PresShell::GetResolution() works for oop-frames

Status: RESOLVED FIXED

(Core :: Layout, enhancement, P3)

Description

[Jonathan Watt [:jwatt]]

Various bits of code look up the root presContext's presShell and call GetResolution() on it. For example, APZCCallbackHelper::ApplyCallbackTransform does this to “scale [the passed point] inversely [to undo] the scale-to-resolution transform that the compositor adds to the layer”.

Keeping this resolution in sync across oop-frames still requires some thought. Zooming followed by a tap, for example, may end up sending events to the wrong place. Kats had some thoughts on this.

Comment 1

[Jonathan Watt [:jwatt]]

needinfo is just to make sure you're aware of this bug in case it duplicates anything gfx is working on.

Comment 2

[Jonathan Watt [:jwatt]]

Botond, I understand you're working on pinch zoom for desktop. Just needinfo'ing you so you're aware of this in case it's covered elsewhere.

Comment 3

[Botond Ballo [:botond]]

We don't need this for desktop zooming itself, but we'll need it for the combination of desktop zooming + fission. I'll keep it in mind.

Comment 4

[Neha Kochar [:neha]]

This will affect pinch zooming which is shipping already, so M6c.

Comment 5

[Hiroyuki Ikezoe (:hiro)]

I think we can close this for now.

A suspicious place we thought we need to change was ViewportUtils::GetVisualToLayoutTransform, but it turns out we don't need it as I commented in bug 1649447 comment 12.

I did skim all call sites quickly, most of them look it should work as it is (I am not sure about accessibility stuff though).

Anyway, a basic principal fact is that we should handle the desktop zooming value via BrowserChild::mChildToParentConversionMatrix for OOP iframe documents if it's necessary. (Most of the call sites of GetResolution() don't need it though as far as I can tell) That means we need to change the call sites instead of GetResolution().

CCing Jamie. Jamie if you noticed any issue related to PresShell::GetResolution() calls in accessibility stuff (I am putting a searchfox link for all call sites of the function), please open a new bug, I can probably help to fix the issue. Thanks!

Closing.