From 26a029d407be480d791972afb5975cf62c9360a6 Mon Sep 17 00:00:00 2001
From: Daniel Baumann <daniel.baumann@progress-linux.org>
Date: Fri, 19 Apr 2024 02:47:55 +0200
Subject: Adding upstream version 124.0.1.

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
---
 .../available-block-size-htb-vrl.https.html        | 65 +++++++++++++++++++++
 .../available-block-size-invalid.https.html        | 49 ++++++++++++++++
 .../available-block-size-vrl-htb.https.html        | 65 +++++++++++++++++++++
 .../available-inline-size-htb-htb.https.html       | 65 +++++++++++++++++++++
 .../available-inline-size-invalid.https.html       | 49 ++++++++++++++++
 .../available-inline-size-vrl-vrl.https.html       | 65 +++++++++++++++++++++
 ...ailable-size-for-percentages-htb-htb.https.html | 59 +++++++++++++++++++
 ...ailable-size-for-percentages-htb-vrl.https.html | 59 +++++++++++++++++++
 ...ailable-size-for-percentages-invalid.https.html | 49 ++++++++++++++++
 ...ailable-size-for-percentages-vrl-htb.https.html | 59 +++++++++++++++++++
 ...ailable-size-for-percentages-vrl-vrl.https.html | 59 +++++++++++++++++++
 .../fixed-block-size-vrl.https.html                | 60 +++++++++++++++++++
 .../child-constraints/fixed-block-size.https.html  | 59 +++++++++++++++++++
 .../fixed-inline-size-vrl.https.html               | 60 +++++++++++++++++++
 .../child-constraints/fixed-inline-size.https.html | 59 +++++++++++++++++++
 .../percentage-size-htb-htb.https.html             | 58 +++++++++++++++++++
 .../percentage-size-htb-vrl.https.html             | 58 +++++++++++++++++++
 .../percentage-size-invalid.https.html             | 47 +++++++++++++++
 .../percentage-size-quirks-mode.https.html         | 55 ++++++++++++++++++
 .../percentage-size-vrl-htb.https.html             | 58 +++++++++++++++++++
 .../percentage-size-vrl-vrl.https.html             | 58 +++++++++++++++++++
 .../support/layout-child-sizes-worklet.js          | 67 ++++++++++++++++++++++
 22 files changed, 1282 insertions(+)
 create mode 100644 testing/web-platform/tests/css/css-layout-api/child-constraints/available-block-size-htb-vrl.https.html
 create mode 100644 testing/web-platform/tests/css/css-layout-api/child-constraints/available-block-size-invalid.https.html
 create mode 100644 testing/web-platform/tests/css/css-layout-api/child-constraints/available-block-size-vrl-htb.https.html
 create mode 100644 testing/web-platform/tests/css/css-layout-api/child-constraints/available-inline-size-htb-htb.https.html
 create mode 100644 testing/web-platform/tests/css/css-layout-api/child-constraints/available-inline-size-invalid.https.html
 create mode 100644 testing/web-platform/tests/css/css-layout-api/child-constraints/available-inline-size-vrl-vrl.https.html
 create mode 100644 testing/web-platform/tests/css/css-layout-api/child-constraints/available-size-for-percentages-htb-htb.https.html
 create mode 100644 testing/web-platform/tests/css/css-layout-api/child-constraints/available-size-for-percentages-htb-vrl.https.html
 create mode 100644 testing/web-platform/tests/css/css-layout-api/child-constraints/available-size-for-percentages-invalid.https.html
 create mode 100644 testing/web-platform/tests/css/css-layout-api/child-constraints/available-size-for-percentages-vrl-htb.https.html
 create mode 100644 testing/web-platform/tests/css/css-layout-api/child-constraints/available-size-for-percentages-vrl-vrl.https.html
 create mode 100644 testing/web-platform/tests/css/css-layout-api/child-constraints/fixed-block-size-vrl.https.html
 create mode 100644 testing/web-platform/tests/css/css-layout-api/child-constraints/fixed-block-size.https.html
 create mode 100644 testing/web-platform/tests/css/css-layout-api/child-constraints/fixed-inline-size-vrl.https.html
 create mode 100644 testing/web-platform/tests/css/css-layout-api/child-constraints/fixed-inline-size.https.html
 create mode 100644 testing/web-platform/tests/css/css-layout-api/child-constraints/percentage-size-htb-htb.https.html
 create mode 100644 testing/web-platform/tests/css/css-layout-api/child-constraints/percentage-size-htb-vrl.https.html
 create mode 100644 testing/web-platform/tests/css/css-layout-api/child-constraints/percentage-size-invalid.https.html
 create mode 100644 testing/web-platform/tests/css/css-layout-api/child-constraints/percentage-size-quirks-mode.https.html
 create mode 100644 testing/web-platform/tests/css/css-layout-api/child-constraints/percentage-size-vrl-htb.https.html
 create mode 100644 testing/web-platform/tests/css/css-layout-api/child-constraints/percentage-size-vrl-vrl.https.html
 create mode 100644 testing/web-platform/tests/css/css-layout-api/child-constraints/support/layout-child-sizes-worklet.js

(limited to 'testing/web-platform/tests/css/css-layout-api/child-constraints')

diff --git a/testing/web-platform/tests/css/css-layout-api/child-constraints/available-block-size-htb-vrl.https.html b/testing/web-platform/tests/css/css-layout-api/child-constraints/available-block-size-htb-vrl.https.html
new file mode 100644
index 0000000000..6ec8e4062f
--- /dev/null
+++ b/testing/web-platform/tests/css/css-layout-api/child-constraints/available-block-size-htb-vrl.https.html
@@ -0,0 +1,65 @@
+<!DOCTYPE html>
+<html class=reftest-wait>
+<link rel="help" href="https://drafts.css-houdini.org/css-layout-api/#dom-layoutconstraintsoptions-availableblocksize">
+<link rel="match" href="../green-square-ref.html">
+<meta name="assert" content="This test checks that setting the available block-size of children works as expected." />
+
+<style>
+.test {
+  writing-mode: horizontal-tb;
+  background: red;
+  width: 100px;
+}
+
+.child {
+  writing-mode: vertical-rl;
+  visibility: hidden;
+  line-height: 0;
+
+  --available-block-size: 20;
+}
+
+.inline {
+  display: inline-block;
+  width: 8px;
+}
+
+.inline-size-10 { height: 10px; }
+.inline-size-30 { height: 30px; }
+
+@supports (display: layout(test)) {
+  .test {
+    background: green;
+    display: layout(test);
+  }
+}
+</style>
+<script src="/common/reftest-wait.js"></script>
+<script src="/common/worklet-reftest.js"></script>
+
+<div class="test">
+  <!-- As the inlines don't fit within 20px, we'll end up with two lines. -->
+  <div class="child" style="--block-size-expected: 30; --inline-size-expected: 16;">
+    <span class="inline inline-size-10"></span>
+    <span class="inline inline-size-30"></span>
+  </div>
+
+  <!-- The single inline doesn't take up the whole 20px, so will be shrink fitted. -->
+  <div class="child" style="--block-size-expected: 10; --inline-size-expected: 8;">
+    <span class="inline inline-size-10"></span>
+  </div>
+
+  <!-- Make sure the max-height property clamps the size. -->
+  <div class="child" style="max-height: 25px; --block-size-expected: 25; --inline-size-expected: 8;">
+    <span class="inline inline-size-30"></span>
+  </div>
+
+  <!-- Make sure the min-height property clamps the size. -->
+  <div class="child" style="min-height: 25px; --block-size-expected: 25; --inline-size-expected: 8;">
+    <span class="inline inline-size-10"></span>
+  </div>
+</div>
+
+<script>
+importWorkletAndTerminateTestAfterAsyncPaint(CSS.layoutWorklet, {url: 'support/layout-child-sizes-worklet.js'});
+</script>
diff --git a/testing/web-platform/tests/css/css-layout-api/child-constraints/available-block-size-invalid.https.html b/testing/web-platform/tests/css/css-layout-api/child-constraints/available-block-size-invalid.https.html
new file mode 100644
index 0000000000..32a0f11a4e
--- /dev/null
+++ b/testing/web-platform/tests/css/css-layout-api/child-constraints/available-block-size-invalid.https.html
@@ -0,0 +1,49 @@
+<!DOCTYPE html>
+<html class=reftest-wait>
+<link rel="help" href="https://drafts.css-houdini.org/css-layout-api/#dom-layoutconstraintsoptions-availableblocksize">
+<link rel="match" href="../green-square-ref.html">
+<meta name="assert" content="This test checks that setting an invalid available block-size works as expected." />
+
+<style>
+.test {
+  writing-mode: horizontal-tb;
+  background: red;
+  width: 100px;
+}
+
+.child {
+  writing-mode: vertical-rl;
+  visibility: hidden;
+  line-height: 0;
+
+  --available-block-size: -20;
+}
+
+.inline {
+  display: inline-block;
+  width: 8px;
+}
+
+.inline-size-10 { height: 10px; }
+
+@supports (display: layout(test)) {
+  .test {
+    background: green;
+    display: layout(test);
+  }
+}
+</style>
+<script src="/common/reftest-wait.js"></script>
+<script src="/common/worklet-reftest.js"></script>
+
+<div class="test">
+  <!-- The invalid available block-size should be clamped to zero. -->
+  <div class="child" style="--block-size-expected: 10; --inline-size-expected: 16;">
+    <span class="inline inline-size-10"></span>
+    <span class="inline inline-size-10"></span>
+  </div>
+</div>
+
+<script>
+importWorkletAndTerminateTestAfterAsyncPaint(CSS.layoutWorklet, {url: 'support/layout-child-sizes-worklet.js'});
+</script>
diff --git a/testing/web-platform/tests/css/css-layout-api/child-constraints/available-block-size-vrl-htb.https.html b/testing/web-platform/tests/css/css-layout-api/child-constraints/available-block-size-vrl-htb.https.html
new file mode 100644
index 0000000000..536af3b5a4
--- /dev/null
+++ b/testing/web-platform/tests/css/css-layout-api/child-constraints/available-block-size-vrl-htb.https.html
@@ -0,0 +1,65 @@
+<!DOCTYPE html>
+<html class=reftest-wait>
+<link rel="help" href="https://drafts.css-houdini.org/css-layout-api/#dom-layoutconstraintsoptions-availableblocksize">
+<link rel="match" href="../green-square-ref.html">
+<meta name="assert" content="This test checks that setting the available block-size of children works as expected." />
+
+<style>
+.test {
+  writing-mode: vertical-rl;
+  background: red;
+  height: 100px;
+}
+
+.child {
+  writing-mode: horizontal-tb;
+  visibility: hidden;
+  line-height: 0;
+
+  --available-block-size: 20;
+}
+
+.inline {
+  display: inline-block;
+  height: 8px;
+}
+
+.inline-size-10 { width: 10px; }
+.inline-size-30 { width: 30px; }
+
+@supports (display: layout(test)) {
+  .test {
+    background: green;
+    display: layout(test);
+  }
+}
+</style>
+<script src="/common/reftest-wait.js"></script>
+<script src="/common/worklet-reftest.js"></script>
+
+<div class="test">
+  <!-- As the inlines don't fit within 20px, we'll end up with two lines. -->
+  <div class="child" style="--block-size-expected: 30; --inline-size-expected: 16;">
+    <span class="inline inline-size-10"></span>
+    <span class="inline inline-size-30"></span>
+  </div>
+
+  <!-- The single inline doesn't take up the whole 20px, so will be shrink fitted. -->
+  <div class="child" style="--block-size-expected: 10; --inline-size-expected: 8;">
+    <span class="inline inline-size-10"></span>
+  </div>
+
+  <!-- Make sure the max-width property clamps the size. -->
+  <div class="child" style="max-width: 25px; --block-size-expected: 25; --inline-size-expected: 8;">
+    <span class="inline inline-size-30"></span>
+  </div>
+
+  <!-- Make sure the min-width property clamps the size. -->
+  <div class="child" style="min-width: 25px; --block-size-expected: 25; --inline-size-expected: 8;">
+    <span class="inline inline-size-10"></span>
+  </div>
+</div>
+
+<script>
+importWorkletAndTerminateTestAfterAsyncPaint(CSS.layoutWorklet, {url: 'support/layout-child-sizes-worklet.js'});
+</script>
diff --git a/testing/web-platform/tests/css/css-layout-api/child-constraints/available-inline-size-htb-htb.https.html b/testing/web-platform/tests/css/css-layout-api/child-constraints/available-inline-size-htb-htb.https.html
new file mode 100644
index 0000000000..6205c01d10
--- /dev/null
+++ b/testing/web-platform/tests/css/css-layout-api/child-constraints/available-inline-size-htb-htb.https.html
@@ -0,0 +1,65 @@
+<!DOCTYPE html>
+<html class=reftest-wait>
+<link rel="help" href="https://drafts.css-houdini.org/css-layout-api/#dom-layoutconstraintsoptions-availableinlinesize">
+<link rel="match" href="../green-square-ref.html">
+<meta name="assert" content="This test checks that setting the available inline-size of children works as expected." />
+
+<style>
+.test {
+  writing-mode: horizontal-tb;
+  background: red;
+  width: 100px;
+}
+
+.child {
+  writing-mode: horizontal-tb;
+  visibility: hidden;
+  line-height: 0;
+
+  --available-inline-size: 20;
+}
+
+.inline {
+  display: inline-block;
+  height: 8px;
+}
+
+.inline-size-10 { width: 10px; }
+.inline-size-30 { width: 30px; }
+
+@supports (display: layout(test)) {
+  .test {
+    background: green;
+    display: layout(test);
+  }
+}
+</style>
+<script src="/common/reftest-wait.js"></script>
+<script src="/common/worklet-reftest.js"></script>
+
+<div class="test">
+  <!-- As the inlines don't fit within 20px, we'll end up with two lines. -->
+  <div class="child" style="--inline-size-expected: 30; --block-size-expected: 16;">
+    <span class="inline inline-size-10"></span>
+    <span class="inline inline-size-30"></span>
+  </div>
+
+  <!-- The single inline doesn't take up the whole 20px, so will be shrink fitted. -->
+  <div class="child" style="--inline-size-expected: 10; --block-size-expected: 8;">
+    <span class="inline inline-size-10"></span>
+  </div>
+
+  <!-- Make sure the max-width property clamps the size. -->
+  <div class="child" style="max-width: 25px; --inline-size-expected: 25; --block-size-expected: 8;">
+    <span class="inline inline-size-30"></span>
+  </div>
+
+  <!-- Make sure the min-width property clamps the size. -->
+  <div class="child" style="min-width: 25px; --inline-size-expected: 25; --block-size-expected: 8;">
+    <span class="inline inline-size-10"></span>
+  </div>
+</div>
+
+<script>
+importWorkletAndTerminateTestAfterAsyncPaint(CSS.layoutWorklet, {url: 'support/layout-child-sizes-worklet.js'});
+</script>
diff --git a/testing/web-platform/tests/css/css-layout-api/child-constraints/available-inline-size-invalid.https.html b/testing/web-platform/tests/css/css-layout-api/child-constraints/available-inline-size-invalid.https.html
new file mode 100644
index 0000000000..8bb18aaa4b
--- /dev/null
+++ b/testing/web-platform/tests/css/css-layout-api/child-constraints/available-inline-size-invalid.https.html
@@ -0,0 +1,49 @@
+<!DOCTYPE html>
+<html class=reftest-wait>
+<link rel="help" href="https://drafts.css-houdini.org/css-layout-api/#dom-layoutconstraintsoptions-availableinlinesize">
+<link rel="match" href="../green-square-ref.html">
+<meta name="assert" content="This test checks that setting an invalid available inline-size works as expected." />
+
+<style>
+.test {
+  writing-mode: horizontal-tb;
+  background: red;
+  width: 100px;
+}
+
+.child {
+  writing-mode: horizontal-tb;
+  visibility: hidden;
+  line-height: 0;
+
+  --available-inline-size: -20;
+}
+
+.inline {
+  display: inline-block;
+  height: 8px;
+}
+
+.inline-size-10 { width: 10px; }
+
+@supports (display: layout(test)) {
+  .test {
+    background: green;
+    display: layout(test);
+  }
+}
+</style>
+<script src="/common/reftest-wait.js"></script>
+<script src="/common/worklet-reftest.js"></script>
+
+<div class="test">
+  <!-- The invalid available inline-size should be clamped to zero. -->
+  <div class="child" style="--inline-size-expected: 10; --block-size-expected: 16;">
+    <span class="inline inline-size-10"></span>
+    <span class="inline inline-size-10"></span>
+  </div>
+</div>
+
+<script>
+importWorkletAndTerminateTestAfterAsyncPaint(CSS.layoutWorklet, {url: 'support/layout-child-sizes-worklet.js'});
+</script>
diff --git a/testing/web-platform/tests/css/css-layout-api/child-constraints/available-inline-size-vrl-vrl.https.html b/testing/web-platform/tests/css/css-layout-api/child-constraints/available-inline-size-vrl-vrl.https.html
new file mode 100644
index 0000000000..1b8d01f024
--- /dev/null
+++ b/testing/web-platform/tests/css/css-layout-api/child-constraints/available-inline-size-vrl-vrl.https.html
@@ -0,0 +1,65 @@
+<!DOCTYPE html>
+<html class=reftest-wait>
+<link rel="help" href="https://drafts.css-houdini.org/css-layout-api/#dom-layoutconstraintsoptions-availableinlinesize">
+<link rel="match" href="../green-square-ref.html">
+<meta name="assert" content="This test checks that setting the available inline-size of children works as expected." />
+
+<style>
+.test {
+  writing-mode: vertical-rl;
+  background: red;
+  height: 100px;
+}
+
+.child {
+  writing-mode: vertical-rl;
+  visibility: hidden;
+  line-height: 0;
+
+  --available-inline-size: 20;
+}
+
+.inline {
+  display: inline-block;
+  width: 8px;
+}
+
+.inline-size-10 { height: 10px; }
+.inline-size-30 { height: 30px; }
+
+@supports (display: layout(test)) {
+  .test {
+    background: green;
+    display: layout(test);
+  }
+}
+</style>
+<script src="/common/reftest-wait.js"></script>
+<script src="/common/worklet-reftest.js"></script>
+
+<div class="test">
+  <!-- As the inlines don't fit within 20px, we'll end up with two lines. -->
+  <div class="child" style="--inline-size-expected: 30; --block-size-expected: 16;">
+    <span class="inline inline-size-10"></span>
+    <span class="inline inline-size-30"></span>
+  </div>
+
+  <!-- The single inline doesn't take up the whole 20px, so will be shrink fitted. -->
+  <div class="child" style="--inline-size-expected: 10; --block-size-expected: 8;">
+    <span class="inline inline-size-10"></span>
+  </div>
+
+  <!-- Make sure the max-height property clamps the size. -->
+  <div class="child" style="max-height: 25px; --inline-size-expected: 25; --block-size-expected: 8;">
+    <span class="inline inline-size-30"></span>
+  </div>
+
+  <!-- Make sure the min-height property clamps the size. -->
+  <div class="child" style="min-height: 25px; --inline-size-expected: 25; --block-size-expected: 8;">
+    <span class="inline inline-size-10"></span>
+  </div>
+</div>
+
+<script>
+importWorkletAndTerminateTestAfterAsyncPaint(CSS.layoutWorklet, {url: 'support/layout-child-sizes-worklet.js'});
+</script>
diff --git a/testing/web-platform/tests/css/css-layout-api/child-constraints/available-size-for-percentages-htb-htb.https.html b/testing/web-platform/tests/css/css-layout-api/child-constraints/available-size-for-percentages-htb-htb.https.html
new file mode 100644
index 0000000000..9bf4d40ad6
--- /dev/null
+++ b/testing/web-platform/tests/css/css-layout-api/child-constraints/available-size-for-percentages-htb-htb.https.html
@@ -0,0 +1,59 @@
+<!DOCTYPE html>
+<html class=reftest-wait>
+<link rel="help" href="https://drafts.css-houdini.org/css-layout-api/#dom-layoutconstraintsoptions-availableinlinesize">
+<link rel="help" href="https://drafts.css-houdini.org/css-layout-api/#dom-layoutconstraintsoptions-availableblocksize">
+<link rel="match" href="../green-square-ref.html">
+<meta name="assert" content="This test checks that resolving percentages against the available size works as expected." />
+
+<style>
+.test {
+  writing-mode: horizontal-tb;
+  background: red;
+  width: 100px;
+}
+
+.child {
+  writing-mode: horizontal-tb;
+  visibility: hidden;
+
+  --available-inline-size: 50;
+  --available-block-size: 20;
+
+  --inline-size-expected: 10px;
+  --block-size-expected: 10px;
+}
+
+@supports (display: layout(test)) {
+  .test {
+    background: green;
+    display: layout(test);
+  }
+}
+</style>
+<script src="/common/reftest-wait.js"></script>
+<script src="/common/worklet-reftest.js"></script>
+
+<div class="test">
+  <!-- A fixed width/height shouldn't be affected by the available size. -->
+  <div class="child" style="width: 10px; height: 10px;"></div>
+
+  <!-- A percentage width/height should resolve itself against the available size. -->
+  <div class="child" style="width: 20%; height: 50%;"></div>
+
+  <!-- A percentage max-width/max-height should resolve itself against the available size. -->
+  <div class="child" style="width: 15px; max-width: 20%; height: 15px; max-height: 50%;"></div>
+
+  <!-- A percentage min-width/min-height should resolve itself against the available size. -->
+  <div class="child" style="width: 5px; min-width: 20%; height: 5px; min-height: 50%;"></div>
+
+  <!-- A replaced percentage width/height should resolve itself against the available size. -->
+  <img class="child" style="width: 20%; height: 50%;" />
+
+  <!-- A replaced percentage max-width/max-height should resolve itself against the available size. -->
+  <img class="child" style="width: 15px; max-width: 20%; height: 15px; max-height: 50%;" />
+
+  <!-- A replaced percentage min-width/min-height should resolve itself against the available size. -->
+  <img class="child" style="width: 5px; min-width: 20%; height: 5px; min-height: 50%;" />
+<script>
+importWorkletAndTerminateTestAfterAsyncPaint(CSS.layoutWorklet, {url: 'support/layout-child-sizes-worklet.js'});
+</script>
diff --git a/testing/web-platform/tests/css/css-layout-api/child-constraints/available-size-for-percentages-htb-vrl.https.html b/testing/web-platform/tests/css/css-layout-api/child-constraints/available-size-for-percentages-htb-vrl.https.html
new file mode 100644
index 0000000000..eb104a180d
--- /dev/null
+++ b/testing/web-platform/tests/css/css-layout-api/child-constraints/available-size-for-percentages-htb-vrl.https.html
@@ -0,0 +1,59 @@
+<!DOCTYPE html>
+<html class=reftest-wait>
+<link rel="help" href="https://drafts.css-houdini.org/css-layout-api/#dom-layoutconstraintsoptions-availableinlinesize">
+<link rel="help" href="https://drafts.css-houdini.org/css-layout-api/#dom-layoutconstraintsoptions-availableblocksize">
+<link rel="match" href="../green-square-ref.html">
+<meta name="assert" content="This test checks that resolving percentages against the available size works as expected." />
+
+<style>
+.test {
+  writing-mode: horizontal-tb;
+  background: red;
+  width: 100px;
+}
+
+.child {
+  writing-mode: vertical-rl;
+  visibility: hidden;
+
+  --available-inline-size: 50;
+  --available-block-size: 20;
+
+  --inline-size-expected: 10px;
+  --block-size-expected: 10px;
+}
+
+@supports (display: layout(test)) {
+  .test {
+    background: green;
+    display: layout(test);
+  }
+}
+</style>
+<script src="/common/reftest-wait.js"></script>
+<script src="/common/worklet-reftest.js"></script>
+
+<div class="test">
+  <!-- A fixed width/height shouldn't be affected by the available size. -->
+  <div class="child" style="width: 10px; height: 10px;"></div>
+
+  <!-- A percentage width/height should resolve itself against the available size. -->
+  <div class="child" style="width: 20%; height: 50%;"></div>
+
+  <!-- A percentage max-width/max-height should resolve itself against the available size. -->
+  <div class="child" style="width: 15px; max-width: 20%; height: 15px; max-height: 50%;"></div>
+
+  <!-- A percentage min-width/min-height should resolve itself against the available size. -->
+  <div class="child" style="width: 5px; min-width: 20%; height: 5px; min-height: 50%;"></div>
+
+  <!-- A replaced percentage width/height should resolve itself against the available size. -->
+  <img class="child" style="width: 20%; height: 50%;" />
+
+  <!-- A replaced percentage max-width/max-height should resolve itself against the available size. -->
+  <img class="child" style="width: 15px; max-width: 20%; height: 15px; max-height: 50%;" />
+
+  <!-- A replaced percentage min-width/min-height should resolve itself against the available size. -->
+  <img class="child" style="width: 5px; min-width: 20%; height: 5px; min-height: 50%;" />
+<script>
+importWorkletAndTerminateTestAfterAsyncPaint(CSS.layoutWorklet, {url: 'support/layout-child-sizes-worklet.js'});
+</script>
diff --git a/testing/web-platform/tests/css/css-layout-api/child-constraints/available-size-for-percentages-invalid.https.html b/testing/web-platform/tests/css/css-layout-api/child-constraints/available-size-for-percentages-invalid.https.html
new file mode 100644
index 0000000000..8bd969271e
--- /dev/null
+++ b/testing/web-platform/tests/css/css-layout-api/child-constraints/available-size-for-percentages-invalid.https.html
@@ -0,0 +1,49 @@
+<!DOCTYPE html>
+<html class=reftest-wait>
+<link rel="help" href="https://drafts.css-houdini.org/css-layout-api/#dom-layoutconstraintsoptions-availableinlinesize">
+<link rel="help" href="https://drafts.css-houdini.org/css-layout-api/#dom-layoutconstraintsoptions-availableblocksize">
+<link rel="match" href="../green-square-ref.html">
+<meta name="assert" content="This test checks that resolving percentages against an invalid available size works as expected." />
+
+<style>
+.test {
+  background: red;
+  width: 100px;
+}
+
+.child {
+  visibility: hidden;
+  width: 10px;
+  line-height: 0;
+
+  --available-inline-size: -20;
+  --available-block-size: -10;
+}
+
+.inline {
+  display: inline-block;
+  width: 10px;
+  height: 10px;
+}
+
+@supports (display: layout(test)) {
+  .test {
+    background: green;
+    display: layout(test);
+  }
+}
+</style>
+<script src="/common/reftest-wait.js"></script>
+<script src="/common/worklet-reftest.js"></script>
+
+<div class="test">
+  <!-- The available inline-size gets clamped to zero, and the available block-size gets treated as indefinite. -->
+  <div class="child" style="--inline-size-expected: 0px; --block-size-expected: 10px; width: 100%; height: 100%;">
+    <div class="inline"></div>
+  </div>
+
+  <!-- For replaced elements, both axis should be resolved to 0px. -->
+  <img class="child" style="--inline-size-expected: 0px; --block-size-expected: 0px; width: 100%; height: 100%;" />
+<script>
+importWorkletAndTerminateTestAfterAsyncPaint(CSS.layoutWorklet, {url: 'support/layout-child-sizes-worklet.js'});
+</script>
diff --git a/testing/web-platform/tests/css/css-layout-api/child-constraints/available-size-for-percentages-vrl-htb.https.html b/testing/web-platform/tests/css/css-layout-api/child-constraints/available-size-for-percentages-vrl-htb.https.html
new file mode 100644
index 0000000000..ce8ff95dd0
--- /dev/null
+++ b/testing/web-platform/tests/css/css-layout-api/child-constraints/available-size-for-percentages-vrl-htb.https.html
@@ -0,0 +1,59 @@
+<!DOCTYPE html>
+<html class=reftest-wait>
+<link rel="help" href="https://drafts.css-houdini.org/css-layout-api/#dom-layoutconstraintsoptions-availableinlinesize">
+<link rel="help" href="https://drafts.css-houdini.org/css-layout-api/#dom-layoutconstraintsoptions-availableblocksize">
+<link rel="match" href="../green-square-ref.html">
+<meta name="assert" content="This test checks that resolving percentages against the available size works as expected." />
+
+<style>
+.test {
+  writing-mode: vertical-rl;
+  background: red;
+  height: 100px;
+}
+
+.child {
+  writing-mode: horizontal-tb;
+  visibility: hidden;
+
+  --available-inline-size: 20;
+  --available-block-size: 50;
+
+  --inline-size-expected: 10px;
+  --block-size-expected: 10px;
+}
+
+@supports (display: layout(test)) {
+  .test {
+    background: green;
+    display: layout(test);
+  }
+}
+</style>
+<script src="/common/reftest-wait.js"></script>
+<script src="/common/worklet-reftest.js"></script>
+
+<div class="test">
+  <!-- A fixed width/height shouldn't be affected by the available size. -->
+  <div class="child" style="width: 10px; height: 10px;"></div>
+
+  <!-- A percentage width/height should resolve itself against the available size. -->
+  <div class="child" style="width: 20%; height: 50%;"></div>
+
+  <!-- A percentage max-width/max-height should resolve itself against the available size. -->
+  <div class="child" style="width: 15px; max-width: 20%; height: 15px; max-height: 50%;"></div>
+
+  <!-- A percentage min-width/min-height should resolve itself against the available size. -->
+  <div class="child" style="width: 5px; min-width: 20%; height: 5px; min-height: 50%;"></div>
+
+  <!-- A replaced percentage width/height should resolve itself against the available size. -->
+  <img class="child" style="width: 20%; height: 50%;" />
+
+  <!-- A replaced percentage max-width/max-height should resolve itself against the available size. -->
+  <img class="child" style="width: 15px; max-width: 20%; height: 15px; max-height: 50%;" />
+
+  <!-- A replaced percentage min-width/min-height should resolve itself against the available size. -->
+  <img class="child" style="width: 5px; min-width: 20%; height: 5px; min-height: 50%;" />
+<script>
+importWorkletAndTerminateTestAfterAsyncPaint(CSS.layoutWorklet, {url: 'support/layout-child-sizes-worklet.js'});
+</script>
diff --git a/testing/web-platform/tests/css/css-layout-api/child-constraints/available-size-for-percentages-vrl-vrl.https.html b/testing/web-platform/tests/css/css-layout-api/child-constraints/available-size-for-percentages-vrl-vrl.https.html
new file mode 100644
index 0000000000..71c7355b9c
--- /dev/null
+++ b/testing/web-platform/tests/css/css-layout-api/child-constraints/available-size-for-percentages-vrl-vrl.https.html
@@ -0,0 +1,59 @@
+<!DOCTYPE html>
+<html class=reftest-wait>
+<link rel="help" href="https://drafts.css-houdini.org/css-layout-api/#dom-layoutconstraintsoptions-availableinlinesize">
+<link rel="help" href="https://drafts.css-houdini.org/css-layout-api/#dom-layoutconstraintsoptions-availableblocksize">
+<link rel="match" href="../green-square-ref.html">
+<meta name="assert" content="This test checks that resolving percentages against the available size works as expected." />
+
+<style>
+.test {
+  writing-mode: vertical-rl;
+  background: red;
+  height: 100px;
+}
+
+.child {
+  writing-mode: vertical-rl;
+  visibility: hidden;
+
+  --available-inline-size: 20;
+  --available-block-size: 50;
+
+  --inline-size-expected: 10px;
+  --block-size-expected: 10px;
+}
+
+@supports (display: layout(test)) {
+  .test {
+    background: green;
+    display: layout(test);
+  }
+}
+</style>
+<script src="/common/reftest-wait.js"></script>
+<script src="/common/worklet-reftest.js"></script>
+
+<div class="test">
+  <!-- A fixed width/height shouldn't be affected by the available size. -->
+  <div class="child" style="width: 10px; height: 10px;"></div>
+
+  <!-- A percentage width/height should resolve itself against the available size. -->
+  <div class="child" style="width: 20%; height: 50%;"></div>
+
+  <!-- A percentage max-width/max-height should resolve itself against the available size. -->
+  <div class="child" style="width: 15px; max-width: 20%; height: 15px; max-height: 50%;"></div>
+
+  <!-- A percentage min-width/min-height should resolve itself against the available size. -->
+  <div class="child" style="width: 5px; min-width: 20%; height: 5px; min-height: 50%;"></div>
+
+  <!-- A replaced percentage width/height should resolve itself against the available size. -->
+  <img class="child" style="width: 20%; height: 50%;" />
+
+  <!-- A replaced percentage max-width/max-height should resolve itself against the available size. -->
+  <img class="child" style="width: 15px; max-width: 20%; height: 15px; max-height: 50%;" />
+
+  <!-- A replaced percentage min-width/min-height should resolve itself against the available size. -->
+  <img class="child" style="width: 5px; min-width: 20%; height: 5px; min-height: 50%;" />
+<script>
+importWorkletAndTerminateTestAfterAsyncPaint(CSS.layoutWorklet, {url: 'support/layout-child-sizes-worklet.js'});
+</script>
diff --git a/testing/web-platform/tests/css/css-layout-api/child-constraints/fixed-block-size-vrl.https.html b/testing/web-platform/tests/css/css-layout-api/child-constraints/fixed-block-size-vrl.https.html
new file mode 100644
index 0000000000..631c5f8281
--- /dev/null
+++ b/testing/web-platform/tests/css/css-layout-api/child-constraints/fixed-block-size-vrl.https.html
@@ -0,0 +1,60 @@
+<!DOCTYPE html>
+<html class=reftest-wait>
+<link rel="help" href="https://drafts.css-houdini.org/css-layout-api/#dom-layoutconstraintsoptions-fixedblocksize">
+<link rel="match" href="../green-square-ref.html">
+<meta name="assert" content="This test checks that fixing the block size of children works as expected." />
+
+<style>
+.test {
+  writing-mode: vertical-rl;
+  background: red;
+  height: 100px;
+}
+
+.htb {
+  writing-mode: horizontal-tb;
+  visibility: hidden;
+  width: 3px;
+  height: 2px;
+
+  --fixed-block-size: 10;
+
+  --inline-size-expected: 2;
+  --block-size-expected: 10;
+}
+
+.vrl {
+  writing-mode: vertical-rl;
+  visibility: hidden;
+  width: 3px;
+  height: 2px;
+
+  --fixed-block-size: 10;
+
+  --inline-size-expected: 2;
+  --block-size-expected: 10;
+}
+
+@supports (display: layout(test)) {
+  .test {
+    background: green;
+    display: layout(test);
+  }
+}
+</style>
+<script src="/common/reftest-wait.js"></script>
+<script src="/common/worklet-reftest.js"></script>
+
+<div class="test">
+  <div class="htb"></div>
+  <div class="vrl"></div>
+  <!-- min/max-width should have no effect, fixedBlockSize wins. -->
+  <div class="htb" style="max-width: 5px;"></div>
+  <div class="vrl" style="max-width: 5px;"></div>
+  <div class="htb" style="min-width: 15px;"></div>
+  <div class="vrl" style="min-width: 15px;"></div>
+</div>
+
+<script>
+importWorkletAndTerminateTestAfterAsyncPaint(CSS.layoutWorklet, {url: 'support/layout-child-sizes-worklet.js'});
+</script>
diff --git a/testing/web-platform/tests/css/css-layout-api/child-constraints/fixed-block-size.https.html b/testing/web-platform/tests/css/css-layout-api/child-constraints/fixed-block-size.https.html
new file mode 100644
index 0000000000..737cc4da75
--- /dev/null
+++ b/testing/web-platform/tests/css/css-layout-api/child-constraints/fixed-block-size.https.html
@@ -0,0 +1,59 @@
+<!DOCTYPE html>
+<html class=reftest-wait>
+<link rel="help" href="https://drafts.css-houdini.org/css-layout-api/#dom-layoutconstraintsoptions-fixedblocksize">
+<link rel="match" href="../green-square-ref.html">
+<meta name="assert" content="This test checks that fixing the block size of children works as expected." />
+
+<style>
+.test {
+  background: red;
+  width: 100px;
+}
+
+.htb {
+  writing-mode: horizontal-tb;
+  visibility: hidden;
+  width: 3px;
+  height: 2px;
+
+  --fixed-block-size: 10;
+
+  --inline-size-expected: 3;
+  --block-size-expected: 10;
+}
+
+.vrl {
+  writing-mode: vertical-rl;
+  visibility: hidden;
+  width: 3px;
+  height: 2px;
+
+  --fixed-block-size: 10;
+
+  --inline-size-expected: 3;
+  --block-size-expected: 10;
+}
+
+@supports (display: layout(test)) {
+  .test {
+    background: green;
+    display: layout(test);
+  }
+}
+</style>
+<script src="/common/reftest-wait.js"></script>
+<script src="/common/worklet-reftest.js"></script>
+
+<div class="test">
+  <div class="htb"></div>
+  <div class="vrl"></div>
+  <!-- min/max-height should have no effect, fixedBlockSize wins. -->
+  <div class="htb" style="max-height: 5px;"></div>
+  <div class="vrl" style="max-height: 5px;"></div>
+  <div class="htb" style="min-height: 15px;"></div>
+  <div class="vrl" style="min-height: 15px;"></div>
+</div>
+
+<script>
+importWorkletAndTerminateTestAfterAsyncPaint(CSS.layoutWorklet, {url: 'support/layout-child-sizes-worklet.js'});
+</script>
diff --git a/testing/web-platform/tests/css/css-layout-api/child-constraints/fixed-inline-size-vrl.https.html b/testing/web-platform/tests/css/css-layout-api/child-constraints/fixed-inline-size-vrl.https.html
new file mode 100644
index 0000000000..4fc3c2e77d
--- /dev/null
+++ b/testing/web-platform/tests/css/css-layout-api/child-constraints/fixed-inline-size-vrl.https.html
@@ -0,0 +1,60 @@
+<!DOCTYPE html>
+<html class=reftest-wait>
+<link rel="help" href="https://drafts.css-houdini.org/css-layout-api/#dom-layoutconstraintsoptions-fixedinlinesize">
+<link rel="match" href="../green-square-ref.html">
+<meta name="assert" content="This test checks that fixing the inline size of children works as expected." />
+
+<style>
+.test {
+  writing-mode: vertical-rl;
+  background: red;
+  height: 100px;
+}
+
+.htb {
+  writing-mode: horizontal-tb;
+  visibility: hidden;
+  width: 3px;
+  height: 2px;
+
+  --fixed-inline-size: 10;
+
+  --inline-size-expected: 10;
+  --block-size-expected: 3;
+}
+
+.vrl {
+  writing-mode: vertical-rl;
+  visibility: hidden;
+  width: 3px;
+  height: 2px;
+
+  --fixed-inline-size: 10;
+
+  --inline-size-expected: 10;
+  --block-size-expected: 3;
+}
+
+@supports (display: layout(test)) {
+  .test {
+    background: green;
+    display: layout(test);
+  }
+}
+</style>
+<script src="/common/reftest-wait.js"></script>
+<script src="/common/worklet-reftest.js"></script>
+
+<div class="test">
+  <div class="htb"></div>
+  <div class="vrl"></div>
+  <!-- min/max-height should have no effect, fixedInlineSize wins. -->
+  <div class="htb" style="max-height: 5px;"></div>
+  <div class="vrl" style="max-height: 5px;"></div>
+  <div class="htb" style="min-height: 15px;"></div>
+  <div class="vrl" style="min-height: 15px;"></div>
+</div>
+
+<script>
+importWorkletAndTerminateTestAfterAsyncPaint(CSS.layoutWorklet, {url: 'support/layout-child-sizes-worklet.js'});
+</script>
diff --git a/testing/web-platform/tests/css/css-layout-api/child-constraints/fixed-inline-size.https.html b/testing/web-platform/tests/css/css-layout-api/child-constraints/fixed-inline-size.https.html
new file mode 100644
index 0000000000..0fdf4aca3a
--- /dev/null
+++ b/testing/web-platform/tests/css/css-layout-api/child-constraints/fixed-inline-size.https.html
@@ -0,0 +1,59 @@
+<!DOCTYPE html>
+<html class=reftest-wait>
+<link rel="help" href="https://drafts.css-houdini.org/css-layout-api/#dom-layoutconstraintsoptions-fixedinlinesize">
+<link rel="match" href="../green-square-ref.html">
+<meta name="assert" content="This test checks that fixing the inline size of children works as expected." />
+
+<style>
+.test {
+  background: red;
+  width: 100px;
+}
+
+.htb {
+  writing-mode: horizontal-tb;
+  visibility: hidden;
+  width: 3px;
+  height: 2px;
+
+  --fixed-inline-size: 10;
+
+  --inline-size-expected: 10;
+  --block-size-expected: 2;
+}
+
+.vrl {
+  writing-mode: vertical-rl;
+  visibility: hidden;
+  width: 3px;
+  height: 2px;
+
+  --fixed-inline-size: 10;
+
+  --inline-size-expected: 10;
+  --block-size-expected: 2;
+}
+
+@supports (display: layout(test)) {
+  .test {
+    background: green;
+    display: layout(test);
+  }
+}
+</style>
+<script src="/common/reftest-wait.js"></script>
+<script src="/common/worklet-reftest.js"></script>
+
+<div class="test">
+  <div class="htb"></div>
+  <div class="vrl"></div>
+  <!-- min/max-width should have no effect, fixedInlineSize wins. -->
+  <div class="htb" style="max-width: 5px;"></div>
+  <div class="vrl" style="max-width: 5px;"></div>
+  <div class="htb" style="min-width: 15px;"></div>
+  <div class="vrl" style="min-width: 15px;"></div>
+</div>
+
+<script>
+importWorkletAndTerminateTestAfterAsyncPaint(CSS.layoutWorklet, {url: 'support/layout-child-sizes-worklet.js'});
+</script>
diff --git a/testing/web-platform/tests/css/css-layout-api/child-constraints/percentage-size-htb-htb.https.html b/testing/web-platform/tests/css/css-layout-api/child-constraints/percentage-size-htb-htb.https.html
new file mode 100644
index 0000000000..84bda1ddf5
--- /dev/null
+++ b/testing/web-platform/tests/css/css-layout-api/child-constraints/percentage-size-htb-htb.https.html
@@ -0,0 +1,58 @@
+<!DOCTYPE html>
+<html class=reftest-wait>
+<link rel="help" href="https://drafts.css-houdini.org/css-layout-api/#dom-layoutconstraintsoptions-percentageblocksize">
+<link rel="match" href="../green-square-ref.html">
+<meta name="assert" content="This test checks that setting the percentage block-size of children works as expected." />
+
+<style>
+.test {
+  writing-mode: horizontal-tb;
+  background: red;
+  width: 100px;
+}
+
+.child {
+  writing-mode: horizontal-tb;
+  visibility: hidden;
+  width: 10px;
+
+  --percentage-block-size: 20;
+
+  --inline-size-expected: 10px;
+  --block-size-expected: 10px;
+}
+
+@supports (display: layout(test)) {
+  .test {
+    background: green;
+    display: layout(test);
+  }
+}
+</style>
+<script src="/common/reftest-wait.js"></script>
+<script src="/common/worklet-reftest.js"></script>
+
+<div class="test">
+  <!-- A fixed height shouldn't be affected by the percentage size. -->
+  <div class="child" style="height: 10px;"></div>
+
+  <!-- A percentage height should resolve itself against the percentageBlockSize. -->
+  <div class="child" style="height: 50%;"></div>
+
+  <!-- A percentage max-height should resolve itself against the percentageBlockSize. -->
+  <div class="child" style="height: 15px; max-height: 50%;"></div>
+
+  <!-- A percentage min-height should resolve itself against the percentageBlockSize. -->
+  <div class="child" style="height: 5px; min-height: 50%;"></div>
+
+  <!-- A replaced percentage height should resolve itself against the percentageBlockSize. -->
+  <img class="child" style="height: 50%;" />
+
+  <!-- A replaced percentage max-height should resolve itself against the percentageBlockSize. -->
+  <img class="child" style="height: 15px; max-height: 50%;" />
+
+  <!-- A replaced percentage min-height should resolve itself against the percentageBlockSize. -->
+  <img class="child" style="height: 5px; min-height: 50%;" />
+<script>
+importWorkletAndTerminateTestAfterAsyncPaint(CSS.layoutWorklet, {url: 'support/layout-child-sizes-worklet.js'});
+</script>
diff --git a/testing/web-platform/tests/css/css-layout-api/child-constraints/percentage-size-htb-vrl.https.html b/testing/web-platform/tests/css/css-layout-api/child-constraints/percentage-size-htb-vrl.https.html
new file mode 100644
index 0000000000..98d285b015
--- /dev/null
+++ b/testing/web-platform/tests/css/css-layout-api/child-constraints/percentage-size-htb-vrl.https.html
@@ -0,0 +1,58 @@
+<!DOCTYPE html>
+<html class=reftest-wait>
+<link rel="help" href="https://drafts.css-houdini.org/css-layout-api/#dom-layoutconstraintsoptions-percentageinlinesize">
+<link rel="match" href="../green-square-ref.html">
+<meta name="assert" content="This test checks that setting the percentage inline-size of children works as expected." />
+
+<style>
+.test {
+  writing-mode: horizontal-tb;
+  background: red;
+  width: 100px;
+}
+
+.child {
+  writing-mode: vertical-rl;
+  visibility: hidden;
+  height: 10px;
+
+  --percentage-inline-size: 20;
+
+  --inline-size-expected: 10px;
+  --block-size-expected: 10px;
+}
+
+@supports (display: layout(test)) {
+  .test {
+    background: green;
+    display: layout(test);
+  }
+}
+</style>
+<script src="/common/reftest-wait.js"></script>
+<script src="/common/worklet-reftest.js"></script>
+
+<div class="test">
+  <!-- A fixed width shouldn't be affected by the percentage size. -->
+  <div class="child" style="width: 10px;"></div>
+
+  <!-- A percentage width should resolve itself against the percentageInlineSize. -->
+  <div class="child" style="width: 50%;"></div>
+
+  <!-- A percentage max-width should resolve itself against the percentageInlineSize. -->
+  <div class="child" style="width: 15px; max-width: 50%;"></div>
+
+  <!-- A percentage min-width should resolve itself against the percentageInlineSize. -->
+  <div class="child" style="width: 5px; min-width: 50%;"></div>
+
+  <!-- A replaced percentage width should resolve itself against the percentageInlineSize. -->
+  <img class="child" style="width: 50%;" />
+
+  <!-- A replaced percentage max-width should resolve itself against the percentageInlineSize. -->
+  <img class="child" style="width: 15px; max-width: 50%;" />
+
+  <!-- A replaced percentage min-width should resolve itself against the percentageInlineSize. -->
+  <img class="child" style="width: 5px; min-width: 50%;" />
+<script>
+importWorkletAndTerminateTestAfterAsyncPaint(CSS.layoutWorklet, {url: 'support/layout-child-sizes-worklet.js'});
+</script>
diff --git a/testing/web-platform/tests/css/css-layout-api/child-constraints/percentage-size-invalid.https.html b/testing/web-platform/tests/css/css-layout-api/child-constraints/percentage-size-invalid.https.html
new file mode 100644
index 0000000000..0435535552
--- /dev/null
+++ b/testing/web-platform/tests/css/css-layout-api/child-constraints/percentage-size-invalid.https.html
@@ -0,0 +1,47 @@
+<!DOCTYPE html>
+<html class=reftest-wait>
+<link rel="help" href="https://drafts.css-houdini.org/css-layout-api/#dom-layoutconstraintsoptions-percentageblocksize">
+<link rel="match" href="../green-square-ref.html">
+<meta name="assert" content="This test checks that setting an invalid percentage block-size of children works as expected." />
+
+<style>
+.test {
+  background: red;
+  width: 100px;
+}
+
+.child {
+  visibility: hidden;
+  width: 10px;
+  line-height: 0;
+
+  --percentage-block-size: -10;
+}
+
+.inline {
+  display: inline-block;
+  width: 10px;
+  height: 10px;
+}
+
+@supports (display: layout(test)) {
+  .test {
+    background: green;
+    display: layout(test);
+  }
+}
+</style>
+<script src="/common/reftest-wait.js"></script>
+<script src="/common/worklet-reftest.js"></script>
+
+<div class="test">
+  <!-- A percentage shouldn't be resolved against an invalid percentageBlockSize. -->
+  <div class="child" style="--inline-size-expected: 10px; --block-size-expected: 10px; height: 100%;">
+    <div class="inline"></div>
+  </div>
+
+  <!-- A percentage shouldn't be resolved against an invalid percentageBlockSize. -->
+  <img class="child" style="--inline-size-expected: 10px; --block-size-expected: 0px; height: 100%;" />
+<script>
+importWorkletAndTerminateTestAfterAsyncPaint(CSS.layoutWorklet, {url: 'support/layout-child-sizes-worklet.js'});
+</script>
diff --git a/testing/web-platform/tests/css/css-layout-api/child-constraints/percentage-size-quirks-mode.https.html b/testing/web-platform/tests/css/css-layout-api/child-constraints/percentage-size-quirks-mode.https.html
new file mode 100644
index 0000000000..527149b67a
--- /dev/null
+++ b/testing/web-platform/tests/css/css-layout-api/child-constraints/percentage-size-quirks-mode.https.html
@@ -0,0 +1,55 @@
+<html class=reftest-wait>
+<link rel="help" href="https://drafts.css-houdini.org/css-layout-api/#dom-layoutconstraintsoptions-percentageblocksize">
+<link rel="match" href="../green-square-ref.html">
+<meta name="assert" content="This test checks that setting a percentage block-size works correctly in quirks mode." />
+
+<style>
+.container {
+  height: 200px;
+}
+
+.test {
+  background: red;
+  width: 100px;
+}
+
+.child {
+  visibility: hidden;
+  width: 10px;
+  line-height: 0;
+}
+
+.inline {
+  display: inline-block;
+  width: 10px;
+  height: 10px;
+}
+
+@supports (display: layout(test)) {
+  .test {
+    background: green;
+    display: layout(test);
+  }
+}
+</style>
+<script src="/common/reftest-wait.js"></script>
+<script src="/common/worklet-reftest.js"></script>
+
+<div class="container">
+  <div class="test">
+    <!-- TODO explain. -->
+    <div class="child" style="--percentage-block-size: 50px; --inline-size-expected: 10px; --block-size-expected: 10px;">
+      <div style="height: 20%"></div>
+    </div>
+
+    <!-- TODO explain. -->
+    <div class="child" style="--inline-size-expected: 10px; --block-size-expected: 10px;">
+      <div style="height: 100%">
+        <div class="inline"></div>
+      </div>
+    </div>
+  </div>
+</div>
+<script>
+importWorkletAndTerminateTestAfterAsyncPaint(CSS.layoutWorklet, {url: 'support/layout-child-sizes-worklet.js'});
+</script>
diff --git a/testing/web-platform/tests/css/css-layout-api/child-constraints/percentage-size-vrl-htb.https.html b/testing/web-platform/tests/css/css-layout-api/child-constraints/percentage-size-vrl-htb.https.html
new file mode 100644
index 0000000000..2d3d496fa5
--- /dev/null
+++ b/testing/web-platform/tests/css/css-layout-api/child-constraints/percentage-size-vrl-htb.https.html
@@ -0,0 +1,58 @@
+<!DOCTYPE html>
+<html class=reftest-wait>
+<link rel="help" href="https://drafts.css-houdini.org/css-layout-api/#dom-layoutconstraintsoptions-percentageinlinesize">
+<link rel="match" href="../green-square-ref.html">
+<meta name="assert" content="This test checks that setting the percentage inline-size of children works as expected." />
+
+<style>
+.test {
+  writing-mode: vertical-rl;
+  background: red;
+  height: 100px;
+}
+
+.child {
+  writing-mode: horizontal-tb;
+  visibility: hidden;
+  width: 10px;
+
+  --percentage-inline-size: 20;
+
+  --inline-size-expected: 10px;
+  --block-size-expected: 10px;
+}
+
+@supports (display: layout(test)) {
+  .test {
+    background: green;
+    display: layout(test);
+  }
+}
+</style>
+<script src="/common/reftest-wait.js"></script>
+<script src="/common/worklet-reftest.js"></script>
+
+<div class="test">
+  <!-- A fixed height shouldn't be affected by the percentage size. -->
+  <div class="child" style="height: 10px;"></div>
+
+  <!-- A percentage height should resolve itself against the percentageInlineSize. -->
+  <div class="child" style="height: 50%;"></div>
+
+  <!-- A percentage max-height should resolve itself against the percentageInlineSize. -->
+  <div class="child" style="height: 15px; max-height: 50%;"></div>
+
+  <!-- A percentage min-height should resolve itself against the percentageInlineSize. -->
+  <div class="child" style="height: 5px; min-height: 50%;"></div>
+
+  <!-- A replaced percentage height should resolve itself against the percentageInlineSize. -->
+  <img class="child" style="height: 50%;" />
+
+  <!-- A replaced percentage max-height should resolve itself against the percentageInlineSize. -->
+  <img class="child" style="height: 15px; max-height: 50%;" />
+
+  <!-- A replaced percentage min-height should resolve itself against the percentageInlineSize. -->
+  <img class="child" style="height: 5px; min-height: 50%;" />
+<script>
+importWorkletAndTerminateTestAfterAsyncPaint(CSS.layoutWorklet, {url: 'support/layout-child-sizes-worklet.js'});
+</script>
diff --git a/testing/web-platform/tests/css/css-layout-api/child-constraints/percentage-size-vrl-vrl.https.html b/testing/web-platform/tests/css/css-layout-api/child-constraints/percentage-size-vrl-vrl.https.html
new file mode 100644
index 0000000000..577b98ad98
--- /dev/null
+++ b/testing/web-platform/tests/css/css-layout-api/child-constraints/percentage-size-vrl-vrl.https.html
@@ -0,0 +1,58 @@
+<!DOCTYPE html>
+<html class=reftest-wait>
+<link rel="help" href="https://drafts.css-houdini.org/css-layout-api/#dom-layoutconstraintsoptions-percentageblocksize">
+<link rel="match" href="../green-square-ref.html">
+<meta name="assert" content="This test checks that setting the percentage block-size of children works as expected." />
+
+<style>
+.test {
+  writing-mode: vertical-rl;
+  background: red;
+  height: 100px;
+}
+
+.child {
+  writing-mode: vertical-rl;
+  visibility: hidden;
+  height: 10px;
+
+  --percentage-block-size: 20;
+
+  --inline-size-expected: 10px;
+  --block-size-expected: 10px;
+}
+
+@supports (display: layout(test)) {
+  .test {
+    background: green;
+    display: layout(test);
+  }
+}
+</style>
+<script src="/common/reftest-wait.js"></script>
+<script src="/common/worklet-reftest.js"></script>
+
+<div class="test">
+  <!-- A fixed width shouldn't be affected by the percentage size. -->
+  <div class="child" style="width: 10px;"></div>
+
+  <!-- A percentage width should resolve itself against the percentageBlockSize. -->
+  <div class="child" style="width: 50%;"></div>
+
+  <!-- A percentage max-width should resolve itself against the percentageBlockSize. -->
+  <div class="child" style="width: 15px; max-width: 50%;"></div>
+
+  <!-- A percentage min-width should resolve itself against the percentageBlockSize. -->
+  <div class="child" style="width: 5px; min-width: 50%;"></div>
+
+  <!-- A replaced percentage width should resolve itself against the percentageBlockSize. -->
+  <img class="child" style="width: 50%;" />
+
+  <!-- A replaced percentage max-width should resolve itself against the percentageBlockSize. -->
+  <img class="child" style="width: 15px; max-width: 50%;" />
+
+  <!-- A replaced percentage min-width should resolve itself against the percentageBlockSize. -->
+  <img class="child" style="width: 5px; min-width: 50%;" />
+<script>
+importWorkletAndTerminateTestAfterAsyncPaint(CSS.layoutWorklet, {url: 'support/layout-child-sizes-worklet.js'});
+</script>
diff --git a/testing/web-platform/tests/css/css-layout-api/child-constraints/support/layout-child-sizes-worklet.js b/testing/web-platform/tests/css/css-layout-api/child-constraints/support/layout-child-sizes-worklet.js
new file mode 100644
index 0000000000..5956c9a70c
--- /dev/null
+++ b/testing/web-platform/tests/css/css-layout-api/child-constraints/support/layout-child-sizes-worklet.js
@@ -0,0 +1,67 @@
+import {areArraysEqual} from '/common/arrays.js';
+
+function parseNumber(value) {
+  const num = parseInt(value.toString());
+  if (isNaN(num)) return undefined;
+  return num;
+}
+
+registerLayout('test', class {
+  static get childInputProperties() {
+    return [
+      '--available-inline-size',
+      '--available-block-size',
+      '--fixed-inline-size',
+      '--fixed-block-size',
+      '--percentage-inline-size',
+      '--percentage-block-size',
+      '--inline-size-expected',
+      '--block-size-expected'
+    ];
+  }
+
+  async intrinsicSizes() {}
+  async layout(children, edges, constraints, styleMap) {
+    const childFragments = await Promise.all(children.map((child) => {
+      const childConstraints = {};
+      const availableInlineSize = parseNumber(child.styleMap.get('--available-inline-size'));
+      const availableBlockSize = parseNumber(child.styleMap.get('--available-block-size'));
+      const fixedInlineSize = parseNumber(child.styleMap.get('--fixed-inline-size'));
+      const fixedBlockSize = parseNumber(child.styleMap.get('--fixed-block-size'));
+      const percentageInlineSize = parseNumber(child.styleMap.get('--percentage-inline-size'));
+      const percentageBlockSize = parseNumber(child.styleMap.get('--percentage-block-size'));
+      return child.layoutNextFragment({
+        availableInlineSize,
+        availableBlockSize,
+        fixedInlineSize,
+        fixedBlockSize,
+        percentageInlineSize,
+        percentageBlockSize,
+      });
+    }));
+
+    const actual = childFragments.map((childFragment) => {
+      return {
+        inlineSize: childFragment.inlineSize,
+        blockSize: childFragment.blockSize,
+      };
+    });
+
+    const expected = children.map((child) => {
+      return {
+        inlineSize: parseInt(child.styleMap.get('--inline-size-expected').toString()),
+        blockSize: parseInt(child.styleMap.get('--block-size-expected').toString()),
+      };
+    });
+
+    const equalityFunc = (a, b) => {
+      return a.inlineSize == b.inlineSize && a.blockSize == b.blockSize;
+    };
+
+    if (!areArraysEqual(expected, actual, equalityFunc)) {
+      return {autoBlockSize: 0, childFragments};
+    }
+
+    return {autoBlockSize: 100, childFragments};
+  }
+});
-- 
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