1518640 - Perform anchor selection using the visual viewport

Status: RESOLVED FIXED

(Core :: Layout: Scrolling and Overflow, enhancement, P3)

Description

[Ryan Hunt [:rhunt] (on leave until early May)]

The current scroll anchoring implementation will use the layout viewport for anchor selection.

This means that:

1. An anchor node could be selected some ways above the visual viewport
2. Content after the anchor node could change size
3. This will cause a shift in the content viewed in the visual viewport

We should select an anchor node using the visual viewport.

Comment 1

[Ryan Hunt [:rhunt] (on leave until early May)]

I'm going to unblock the initial release of scroll anchoring, as I think the experience is no worse than without scroll anchoring.

It may still make it into the initial release, it just shouldn't block.

Comment 2

[Ryan Hunt [:rhunt] (on leave until early May)]

Attachment: Bug 1518640 - Use the visual viewport for anchor node selection. r?botond

Comment 3

[Ryan Hunt [:rhunt] (on leave until early May)]

Attachment: Bug 1518640 - Check that a PresShell has a visual viewport offset before returning it. r?botond

This looks like a typo.

Depends on D17048

Comment 4

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/mozilla-inbound/rev/3b192e4631cc
Check that a PresShell has a visual viewport offset before returning it. r=botond
https://hg.mozilla.org/integration/mozilla-inbound/rev/27bbb318ecb4
Use the visual viewport for anchor node selection. r=botond

Comment 5

[Natalia Csoregi [:nataliaCs]]

Backed out for reftest failures on gfx/layers/apz/test/reftest/frame-reconstruction-scroll-clamping.html and mochitest failures on layout/generic/test/test_scroll_position_restore.html

backout: https://hg.mozilla.org/integration/mozilla-inbound/rev/812638586b091e02deebdfca44f97a688a8e2fe4

push with failures: https://treeherder.mozilla.org/#/jobs?repo=mozilla-inbound&resultStatus=testfailed%2Cbusted%2Cexception%2Crunnable&revision=27bbb318ecb4f44c315f87584bdeb1b239d80cef&selectedJob=223354803

failure log for Reftest: https://treeherder.mozilla.org/logviewer.html#/jobs?job_id=223355611&repo=mozilla-inbound&lineNumber=2483

failure log for Mochitest: https://treeherder.mozilla.org/logviewer.html#/jobs?job_id=223354803&repo=mozilla-inbound&lineNumber=12145

Comment 6

[Ryan Hunt [:rhunt] (on leave until early May)]

The problem is in the 'Check that a PresShell has a visual viewport offset before returning it' patch.

From a conversation with Botond on irc, it sounds like the visual viewport size is never set on Desktop, but the visual viewport offset can be. So we're probably running into some untested code. That patch isn't necessary, so I'll just drop it for now.

Comment 7

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/mozilla-inbound/rev/38398e4011d7
Use the visual viewport for anchor node selection. r=botond

Comment 8

[Sebastian Hengst [:aryx] (needinfo me if it's about an intermittent or backout)]

https://hg.mozilla.org/mozilla-central/rev/38398e4011d7