1996832 - Spec Compliance for Anchor Positioning Overflow Detection

Status: RESOLVED FIXED

(Core :: CSS Parsing and Computation, defect)

Description

[David Shin[:dshin]]

Scrollable containing block Bug 1989292

1. Need to check margin rect of positioned frame
2. Need to check against inset reduced containing block
3. Need to ensure positioned rect is originated against abs containing block's padding edge (GetRect() originates from border edge)
4. Need to use scrollable containing block, if default anchor is used and valid: Tracked in (Bug 1989292)

2 has interesting implications here:

• For position-area, the containing block seems extended by the anchor frame.
• For anchor(), auto seems to be treated as 0 - If the default element hangs halfway off the containing block vertically, and an positioned element is anchored to it vertically, whether or not it overflows depends on if the vertical alignment is done through top: anchor(top) or bottom: anchor(bottom). Because the other inset is auto and therefore 0, the positioned frame overflows the IMCB if top is used. This is despite the used value of the other inset being negative to accommodate for the element.

The second part feels pretty counter-intuitive, but going with the used value would make positioned elements using anchor never overflow the IMCB.

Comment 1

[David Shin[:dshin]]

Attachment: position-area seems to extend IMCB by anchor rect

Comment 2

[David Shin[:dshin]]

Attachment: `anchor()` positioning, with non-anchor positioned elements behaving similarly

Comment 3

[David Shin[:dshin]]

Attachment: Bug 1996832: Pass in border-offset padding rect for abspos cb computation. r=#anchor-pos

This gets confusing because insets are computed against the padding rect, but
we store all frame rect information w.r.t. border rect - Add documentation to
make that fact more explicit.

Comment 4

[David Shin[:dshin]]

Attachment: Bug 1996832: Check margin rect of abspos frame for overflowing. r=#anchor-pos

Comment 5

[David Shin[:dshin]]

Attachment: Bug 1996832: Remove unused inset param for margin computation. r=#anchor-pos

Comment 6

[David Shin[:dshin]]

Attachment: Bug 1996832: Use inset modified containing block for abspos frame overflow check. r=#anchor-pos

Comment 7

[David Shin[:dshin]]

Attachment: Bug 1996832: Adjust WPT expectations. r=#anchor-pos

Comment 8

[David Shin[:dshin]]

Attachment: Bug 1996832: Take abs-cb being scrolled into account when testing abspos frame overflowing. r=#anchor-pos

Comment 9

[Pulsebot]

Pushed by [e-mail]:
https://github.com/mozilla-firefox/firefox/commit/cfcfba76dec6
https://hg.mozilla.org/integration/autoland/rev/1af8be116ab8
Pass in border-offset padding rect for abspos cb computation. r=layout-anchor-positioning-reviewers,layout-reviewers,emilio
https://github.com/mozilla-firefox/firefox/commit/d92b01bce062
https://hg.mozilla.org/integration/autoland/rev/f84810b06c0b
Check margin rect of abspos frame for overflowing. r=layout-anchor-positioning-reviewers,layout-reviewers,emilio
https://github.com/mozilla-firefox/firefox/commit/8e441104183c
https://hg.mozilla.org/integration/autoland/rev/f9cde34dfde1
Remove unused inset param for margin computation. r=layout-anchor-positioning-reviewers,layout-reviewers,emilio
https://github.com/mozilla-firefox/firefox/commit/c85f102c6f77
https://hg.mozilla.org/integration/autoland/rev/047b3e2888a9
Use inset modified containing block for abspos frame overflow check. r=layout-anchor-positioning-reviewers,layout-reviewers,emilio
https://github.com/mozilla-firefox/firefox/commit/022385323b3f
https://hg.mozilla.org/integration/autoland/rev/eb194dbd59c3
Take abs-cb being scrolled into account when testing abspos frame overflowing. r=layout-anchor-positioning-reviewers,layout-reviewers,emilio
https://github.com/mozilla-firefox/firefox/commit/3ad2b7912f23
https://hg.mozilla.org/integration/autoland/rev/aa0e49b48f62
Adjust WPT expectations. r=layout-anchor-positioning-reviewers,emilio

Comment 10

[Iulian Moraru]

https://hg.mozilla.org/mozilla-central/rev/1af8be116ab8
https://hg.mozilla.org/mozilla-central/rev/f84810b06c0b
https://hg.mozilla.org/mozilla-central/rev/f9cde34dfde1
https://hg.mozilla.org/mozilla-central/rev/047b3e2888a9
https://hg.mozilla.org/mozilla-central/rev/eb194dbd59c3
https://hg.mozilla.org/mozilla-central/rev/aa0e49b48f62