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Disable auto margins in combination with position-area [css-anchor-position-1] #52419

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Merged
merged 1 commit into from
Oct 16, 2025
Merged

Disable auto margins in combination with position-area [css-anchor-position-1] #52419

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42 changes: 42 additions & 0 deletions ...d/w3c/web-platform-tests/css/css-anchor-position/auto-margins-position-area-expected.html
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Original file line number Diff line number Diff line change
@@ -0,0 +1,42 @@
<!DOCTYPE html>
<title>CSS Anchor Positioning: position-area vs margins</title>
<style>
.container {
position: absolute;
width: 400px;
height: 400px;
margin: 0 auto;
border: 2px solid;
}
.anchor {
margin-top: 100px;
margin-left: 100px;
width: 150px;
height: 75px;
anchor-name: --anchor;
border: solid 1px;
}

.anchored {
position: absolute;
position-anchor: --anchor;
width: 20px;
height: 20px;
border: solid 1px;
opacity: 30%;
}
</style>
<div class="container">
<div class="anchored" style="background: silver; inset: auto 0 0 auto"></div>
<div class="anchored" style="position-area: span-all; background: maroon"></div>
<div class="anchored" style="position-area: top center; background: orange"></div>
<div class="anchored" style="position-area: left center; background: yellow"></div>
<div class="anchored" style="position-area: bottom right; background: lime"></div>
<div class="anchored" style="position-area: span-right; background: green"></div>
<div class="anchored" style="position-area: span-bottom; background: teal"></div>
<div class="anchored" style="position-area: right; background: blue"></div>
<div class="anchored" style="position-area: bottom; background: purple"></div>
<div class="anchored" style="align-self: anchor-center; background: fuchsia; right: 0"></div>
<div class="anchored" style="justify-self: anchor-center; background: aqua; bottom: 0"></div>
<div class="anchor"></div>
</div>
3 changes: 0 additions & 3 deletions ...ed/w3c/web-platform-tests/css/css-anchor-position/auto-margins-position-area-expected.txt
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This file was deleted.

43 changes: 43 additions & 0 deletions ...ported/w3c/web-platform-tests/css/css-anchor-position/auto-margins-position-area-ref.html
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Original file line number Diff line number Diff line change
@@ -0,0 +1,43 @@
<!DOCTYPE html>
<title>CSS Anchor Positioning: position-area vs margins</title>
<style>
.container {
position: absolute;
width: 400px;
height: 400px;
margin: 0 auto;
border: 2px solid;
}
.anchor {
margin-top: 100px;
margin-left: 100px;
width: 150px;
height: 75px;
anchor-name: --anchor;
border: solid 1px;
}

.anchored {
position: absolute;
position-anchor: --anchor;
width: 20px;
height: 20px;
border: solid 1px;
opacity: 30%;
margin: 0;
}
</style>
<div class="container">
<div class="anchored" style="background: silver; inset: auto 0 0 auto"></div>
<div class="anchored" style="position-area: span-all; background: maroon"></div>
<div class="anchored" style="position-area: top center; background: orange"></div>
<div class="anchored" style="position-area: left center; background: yellow"></div>
<div class="anchored" style="position-area: bottom right; background: lime"></div>
<div class="anchored" style="position-area: span-right; background: green"></div>
<div class="anchored" style="position-area: span-bottom; background: teal"></div>
<div class="anchored" style="position-area: right; background: blue"></div>
<div class="anchored" style="position-area: bottom; background: purple"></div>
<div class="anchored" style="align-self: anchor-center; background: fuchsia; right: 0"></div>
<div class="anchored" style="justify-self: anchor-center; background: aqua; bottom: 0"></div>
<div class="anchor"></div>
</div>
74 changes: 42 additions & 32 deletions ...s/imported/w3c/web-platform-tests/css/css-anchor-position/auto-margins-position-area.html
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Original file line number Diff line number Diff line change
@@ -1,39 +1,49 @@
<!DOCTYPE html>
<link rel="help" href="https://drafts.csswg.org/css-anchor-position-1/">
<style>
.container {
position: relative;
width: 100px;
height: 100px;
border: solid 3px;
}
<title>CSS Anchor Positioning: position-area vs margins</title>
<link rel="help" href="https://drafts.csswg.org/css-anchor-position/#position-area">
<link rel="help" href="https://www.w3.org/TR/css-anchor-position/#anchor-center">

.anchor {
anchor-name: --a;
background: lime;
width: 20px;
height: 20px;
position: relative;
left: 20px;
top: 30px;
}
<link rel="match" href="position-area-margin-auto-ref.html">

.abspos {
background: cornflowerblue;
margin: auto;
position: absolute;
position-area: bottom;
position-anchor: --a;
}
</style>
<style>
.container {
position: absolute;
width: 400px;
height: 400px;
margin: 0 auto;
border: 2px solid;
}
.anchor {
margin-top: 100px;
margin-left: 100px;
width: 150px;
height: 75px;
anchor-name: --anchor;
border: solid 1px;
}

<script src="/resources/testharness.js"></script>
<script src="/resources/testharnessreport.js"></script>
<script src="/resources/check-layout-th.js"></script>
<body onload="checkLayout('.abspos')">
.anchored {
position: absolute;
position-anchor: --anchor;
inset: 0;
width: 20px;
height: 20px;
border: solid 1px;
opacity: 30%;
margin: auto 0 0 auto;
}
</style>
<div class="container">
<div class="anchored" style="background: silver"></div>
<div class="anchored" style="position-area: span-all; background: maroon"></div>
<div class="anchored" style="position-area: top center; background: orange"></div>
<div class="anchored" style="position-area: left center; background: yellow"></div>
<div class="anchored" style="position-area: bottom right; background: lime"></div>
<div class="anchored" style="position-area: span-right; background: green"></div>
<div class="anchored" style="position-area: span-bottom; background: teal"></div>
<div class="anchored" style="position-area: right; background: blue"></div>
<div class="anchored" style="position-area: bottom; background: purple"></div>
<div class="anchored" style="align-self: anchor-center; background: fuchsia"></div>
<div class="anchored" style="justify-self: anchor-center; background: aqua"></div>
<div class="anchor"></div>
<div class="abspos" data-offset-x=10 data-offset-y=65>
<div style="width: 80px; height: 20px;"></div>
</div>
</div>
4 changes: 2 additions & 2 deletions Source/WebCore/rendering/PositionedLayoutConstraints.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -356,8 +356,8 @@ void PositionedLayoutConstraints::resolvePosition(RenderBox::LogicalExtentComput

bool hasAutoBeforeInset = m_insetBefore.isAuto();
bool hasAutoAfterInset = m_insetAfter.isAuto();
bool hasAutoBeforeMargin = m_marginBefore.isAuto();
bool hasAutoAfterMargin = m_marginAfter.isAuto();
bool hasAutoBeforeMargin = m_marginBefore.isAuto() && !m_defaultAnchorBox;
bool hasAutoAfterMargin = m_marginAfter.isAuto() && !m_defaultAnchorBox;

auto distributeSpaceToAutoMargins = [&] {
ASSERT(!hasAutoBeforeInset && !hasAutoAfterInset && (hasAutoBeforeMargin || hasAutoAfterMargin));
Expand Down