1879770 - [css-grid] [css-overflow] Weird interaction between subgrid and scrollbar (or scrollbar-gutter)

Status: RESOLVED FIXED

(Core :: Layout: Scrolling and Overflow, defect)

Description

[Emilio Cobos Álvarez (:emilio)]

Attachment: Test-case (might not consistently reproduce)

STR:

• Open http://software.hixie.ch/utilities/js/live-dom-viewer/saved/12364
• Type a space in the textarea.

ER:

• Nothing, scrollbar-gutter keeps working.

AR:

• The checkboxes somehow go under the scrollbar-gutter until you resize (?)

Ting-Yu, you've been lucking at both grid and scrollbar-gutter, maybe you can take a look?

Comment 1

[Emilio Cobos Álvarez (:emilio)]

Attachment: Screenshot

Comment 2

[Ting-Yu Lin [:TYLin] (PST, UTC-8)]

Attachment: Testcase 2 (100% reproducible after loading)

This bug doesn't require scrollbar-gutter, and is pre-existing with classic scrollbar. I reduced your testcase, and it can be reproduced with subgrid with overflow: scroll.

When a grid container resolves the track size, it calls SubgridComputeMarginBorderPadding [1] if the grid item is a subgrid. The method uses GetActualScrollbarSizes() [2] if the subgrid is a scroll container. However, this is wrong because the subgrid and its scrollbars are not reflowed yet, which is warned on the doc [3].

This bug is not reproducible with original attached testcese because we'll reflow the frame tree twice at [4]. Testcase 2 uses overflow:scroll to uncover this bug because we only reflow the entire frame tree once.

[1] https://searchfox.org/mozilla-central/rev/4fe00e0322377316390da6faa2d645cae53d08f4/layout/generic/nsGridContainerFrame.cpp#6575
[2] https://searchfox.org/mozilla-central/rev/4fe00e0322377316390da6faa2d645cae53d08f4/layout/generic/nsGridContainerFrame.cpp#3702-3703
[3] https://searchfox.org/mozilla-central/rev/4fe00e0322377316390da6faa2d645cae53d08f4/layout/generic/nsIScrollableFrame.h#120-121
[4] https://searchfox.org/mozilla-central/rev/4fe00e0322377316390da6faa2d645cae53d08f4/layout/generic/nsGfxScrollFrame.cpp#1048-1049,1081-1082

Comment 3

[Ting-Yu Lin [:TYLin] (PST, UTC-8)]

Attachment: Bug 1879770 Part 1 - Mark IntrinsicScrollbarGutterSizeAtInlineEdges() const. r?emilio,dholbert

Comment 4

[Ting-Yu Lin [:TYLin] (PST, UTC-8)]

Attachment: Bug 1879770 Part 2 - Add a helper to query intrinsic scrollbar-gutter size for subgrid. r?emilio,dholbert

See https://bugzilla.mozilla.org/show_bug.cgi?id=1879770#c2 for an analysis.

Comment 5

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/8446073fb1d8
Part 1 - Mark IntrinsicScrollbarGutterSizeAtInlineEdges() const. r=emilio
https://hg.mozilla.org/integration/autoland/rev/50bdb6f08609
Part 2 - Add a helper to query intrinsic scrollbar-gutter size for subgrid. r=emilio

Comment 6

[Web Platform Test Sync Bot [:wpt-sync] (Matrix: #interop:mozilla.org)]

Created web-platform-tests PR https://github.com/web-platform-tests/wpt/pull/44903 for changes under testing/web-platform/tests

Comment 7

[Narcis Beleuzu [:NarcisB]]

https://hg.mozilla.org/mozilla-central/rev/8446073fb1d8
https://hg.mozilla.org/mozilla-central/rev/50bdb6f08609

Comment 8

[Web Platform Test Sync Bot [:wpt-sync] (Matrix: #interop:mozilla.org)]

Upstream PR merged by moz-wptsync-bot