1995280 - `position-area` grid should be based on union of anchor and containing block rect

Status: RESOLVED FIXED

(Core :: CSS Parsing and Computation, enhancement)

Description

[David Shin[:dshin]]

Attachment: Minimum Reproducible Case

position-area, even if it uses the scrollable block (bug 1989292), the position-area grid can and will move around w.r.t the absolute containing block, if the anchor is inside a scroller that is inside the abs-cb
When the anchor spills out of the abs-cb, the grid should extend to it so that it can receive a consistent size.

See testcase - the anchor is almost off the viewport. In this case, the positioned element should still be positioned & sized against the full anchor, not what is visible.

Comment 1

[David Shin[:dshin]]

Attachment: Bug 1995280: Refactor position-area adjustment to take the anchor rect. r=#anchor-pos

... And separate out default anchor lookup to support it. This avoids having to
carry around a lot of frames and reference data into
AdjustAbsoluteContainingBlockRectForPositionArea.

Comment 2

[David Shin[:dshin]]

Attachment: Bug 1995280: position-area uses the union of CB rect & anchor rect. r=#anchor-pos

Comment 3

[Pulsebot]

Pushed by [e-mail]:
https://github.com/mozilla-firefox/firefox/commit/ca2157db60a3
https://hg.mozilla.org/integration/autoland/rev/23080d4b391a
Refactor position-area adjustment to take the anchor rect. r=layout-anchor-positioning-reviewers,layout-reviewers,emilio
https://github.com/mozilla-firefox/firefox/commit/bea800de3bb2
https://hg.mozilla.org/integration/autoland/rev/a799136b24b4
position-area uses the union of CB rect & anchor rect. r=layout-anchor-positioning-reviewers,layout-reviewers,emilio

Comment 4

[amarc]

https://hg.mozilla.org/mozilla-central/rev/23080d4b391a
https://hg.mozilla.org/mozilla-central/rev/a799136b24b4