Branch: refs/heads/main
Home: https://github.com/WebKit/WebKit
Commit: 428fd736695d230e39867fdfb6a0fc7b1dc29d68
https://github.com/WebKit/WebKit/commit/428fd736695d230e39867fdfb6a0fc7b1dc29d68
Author: Alan Baradlay <[email protected]>
Date: 2026-08-07 (Fri, 07 Aug 2026)
Changed paths:
A
LayoutTests/imported/w3c/web-platform-tests/css/CSS2/normal-flow/block-in-inline-margin-after-relayout-expected.txt
A
LayoutTests/imported/w3c/web-platform-tests/css/CSS2/normal-flow/block-in-inline-margin-after-relayout.html
A
LayoutTests/imported/w3c/web-platform-tests/css/CSS2/normal-flow/block-in-inline-margin-before-relayout-expected.txt
A
LayoutTests/imported/w3c/web-platform-tests/css/CSS2/normal-flow/block-in-inline-margin-before-relayout.html
M Source/WebCore/rendering/RenderBlockFlow.cpp
Log Message:
-----------
[block-in-inline] A block level box's margin after is counted twice when only
that box needs layout
https://bugs.webkit.org/show_bug.cgi?id=321236
Reviewed by Antti Koivisto.
layoutSimpleBlockContentInInline() is the fast-path taken when a container with
inline children needs
layout only because one of its block level boxes does. It walks the block level
boxes, lays each one out,
and takes the MarginInfo the last one leaves behind. The lines are not laid out
at all.
That is fine while the block level box is the only in-flow content, since its
margins are then the
container's own. A line next to the box changes that: the line consumes the
adjacent margin as its own
spacing, so nothing is left to collapse with the container. Normal line layout
accounts for this in
LineBuilder::layoutInlineContent (see updateMarginStateIfNeeded), which does
two things once a line places
contentful inline content - it resets the margin values, and it leaves the
before side of the block. The
shortcut lays out no lines, so it has to do both itself as the walk passes
contentful inline content.
<div><span><div style="margin-bottom: 16px">block</div></span>line
after</div>
reports a 16px margin after on the container once something inside the block
changes and this path runs:
the margin is still in MarginInfo when the caller hands it to
handleAfterSideOfBlock(), so it is counted a
second time.
<div>line before<span><div style="margin-top: 16px">block</div></span></div>
reports a 16px margin before for the same reason. Resetting the margin values
is not enough here, because
canCollapseWithMarginBefore() reads m_atBeforeSideOfBlock rather than the
values, so collapseMargins()
still promotes the block's own margin before into the container's collapsed
margin before and the container
is then repositioned by its parent.
* Source/WebCore/rendering/RenderBlockFlow.cpp:
(WebCore::RenderBlockFlow::layoutSimpleBlockContentInInline):
*
LayoutTests/imported/w3c/web-platform-tests/css/CSS2/normal-flow/block-in-inline-margin-after-relayout.html:
Added.
*
LayoutTests/imported/w3c/web-platform-tests/css/CSS2/normal-flow/block-in-inline-margin-after-relayout-expected.txt:
Added.
*
LayoutTests/imported/w3c/web-platform-tests/css/CSS2/normal-flow/block-in-inline-margin-before-relayout.html:
Added.
*
LayoutTests/imported/w3c/web-platform-tests/css/CSS2/normal-flow/block-in-inline-margin-before-relayout-expected.txt:
Added.
Canonical link: https://commits.webkit.org/318792@main
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