Branch: refs/heads/main
Home: https://github.com/WebKit/WebKit
Commit: 82fcfccdb7e29d4a1ab2de181d15d9067e33ad24
https://github.com/WebKit/WebKit/commit/82fcfccdb7e29d4a1ab2de181d15d9067e33ad24
Author: Alan Baradlay <[email protected]>
Date: 2026-07-14 (Tue, 14 Jul 2026)
Changed paths:
M Source/WebCore/rendering/RenderFlexibleBox.cpp
M Source/WebCore/rendering/RenderFlexibleBox.h
Log Message:
-----------
[cleanup] Snapshot the flex item main-axis margin on FlexLayoutItem instead
of a parallel array
https://bugs.webkit.org/show_bug.cgi?id=318599
Reviewed by Antti Koivisto.
performFlexLayout kept each flex item's main-axis margin extent in a parallel
array
(marginsList) computed up front and threaded through the main-size pipeline.
Snapshot it
onto FlexLayoutItem instead, as the first of the geometry the core reads off
the renderer.
FlexLayoutItem gains a mainAxisMargin field, populated in collectFlexItems from
the flow-aware
margin extent right after the item's flexBaseAndHypotheticalMainSize is
computed. That timing
matters: an orthogonal flex item only resolves its physical margins when it is
laid out for its
flex base size, so the snapshot has to happen after that layout -- reading the
margin at
FlexLayoutItem construction would capture stale, pre-layout values and throw
off margin-trim.
This is the same point the old marginsList was filled (after collectFlexItems
returned). The
field is mutable because margin-trim reduces it during line collection, so
trimMainAxisMarginStart/End now take a FlexLayoutItem& and adjust the field.
The margin-box
helpers (flexBaseMarginBoxSize, hypotheticalMainAxisMarginBoxSize,
flexedMarginBoxSize) and
canFitItemWithTrimmedMarginEnd read the field, and the marginsList array plus
the margin
parameter to computeFlexLines, computeMainSizeForFlexItems,
resolveFlexibleLengthsForLineItems,
handleMainAxisAlignment, and
distributeMainAxisFreeSpaceForMultilineColumnIfNeeded are gone.
No change in behavior: the margin is computed the same way, snapshotted at the
same point, and
follows the same trim. Covered by existing tests (e.g.
imported/w3c/web-platform-tests/css/css-box/margin-trim/flex-row-orthogonal-item.html).
* Source/WebCore/rendering/RenderFlexibleBox.cpp:
* Source/WebCore/rendering/RenderFlexibleBox.h:
Canonical link: https://commits.webkit.org/317164@main
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