Branch: refs/heads/main
Home: https://github.com/WebKit/WebKit
Commit: 25f1db8380ce52433b580f30c232243e0bc07cf7
https://github.com/WebKit/WebKit/commit/25f1db8380ce52433b580f30c232243e0bc07cf7
Author: Sammy Gill <[email protected]>
Date: 2025-08-13 (Wed, 13 Aug 2025)
Changed paths:
M LayoutTests/TestExpectations
M Source/WebCore/rendering/BaselineAlignment.cpp
M Source/WebCore/rendering/RenderFlexibleBox.cpp
Log Message:
-----------
[Flex][Baseline Alignment] Fix flexbox-align-self-vert-rtl-* tests
rdar://157516386
https://bugs.webkit.org/show_bug.cgi?id=296908
Reviewed by Alan Baradlay.
Consider the following flex content with baseline alignment which we
currently fail to align correctly:
<div style="display: flex; width: 200px; flex-direction: column; direction:
rtl; align-items: baseline; outline: 1px solid black;">
<div style="background-color: blue;">foo</div>
<div style="background-color: magenta;">foobarbaz</div>
</div>
When determining the ascent for this flex item, we call into
BaselineAlignmentState::synthesizedBaseline since we need to
synthesize a baseline for this content. This ends up returning
an incorrect value of 0 for both flex items. This baseline comes from
the fact that:
1.) We ask synthesizedBaseline to compute the alphabetic baseline since
the flexbox's writing mode is horizontal-tb.
2.) shouldTreatAsHorizontal is false since the LineDirection is
Vertical, the writing mode (which is the flexbox's writing mode) does not
have sideways orientation, and the writing mode is horizontal-tb.
In order to fix this bug, we need to make two main changes:
1.) Instead of passing in the flexbox's writing mode to
synthesizedBaseline, we should use
BaselineAlignmentState::usedWritingModeForBaselineAlignment.
This is because the writing mode to determine the line under/over edges
needs to come from the CSS-align rules in
https://drafts.csswg.org/css-align-3/#baseline-export
2.) Remove the logic that checks for sideways orientation out of this
function. I introduced this logic in 257239@main and it seems like it was
used to determine which type of baseline (i.e. Alphabetic or Central) to
synthesize. Over time, this logic has moved around the function a bit and
from what I can tell, it no longer needs to live here. The type of
baseline to synthesize is now passed into the function and primarily
comes from BaselineAlignmentState::dominantBaseline.
Canonical link: https://commits.webkit.org/298667@main
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