From fbcef936a97fdce42f54fe011b64f38cb84fd30f Mon Sep 17 00:00:00 2001
From: Callum Law <callumlaw1709@outlook.com>
Date: Fri, 31 Oct 2025 01:14:05 +1300
Subject: [PATCH] LibWeb: Update style before getting animation play state

Pending style updates can influence this value
---
 Libraries/LibWeb/Animations/Animation.cpp     |   8 +
 Libraries/LibWeb/Animations/Animation.h       |   1 +
 Libraries/LibWeb/Animations/Animation.idl     |   2 +-
 .../CSSAnimation-canceling.tentative.txt      |  15 ++
 .../CSSAnimation-playState.tentative.txt      |  10 +
 .../CSSAnimation-canceling.tentative.html     | 196 ++++++++++++++++++
 .../CSSAnimation-playState.tentative.html     |  55 +++++
 7 files changed, 286 insertions(+), 1 deletion(-)
 create mode 100644 Tests/LibWeb/Text/expected/wpt-import/css/css-animations/CSSAnimation-canceling.tentative.txt
 create mode 100644 Tests/LibWeb/Text/expected/wpt-import/css/css-animations/CSSAnimation-playState.tentative.txt
 create mode 100644 Tests/LibWeb/Text/input/wpt-import/css/css-animations/CSSAnimation-canceling.tentative.html
 create mode 100644 Tests/LibWeb/Text/input/wpt-import/css/css-animations/CSSAnimation-playState.tentative.html

diff --git a/Libraries/LibWeb/Animations/Animation.cpp b/Libraries/LibWeb/Animations/Animation.cpp
index 75caac5b52e..936fef9811e 100644
--- a/Libraries/LibWeb/Animations/Animation.cpp
+++ b/Libraries/LibWeb/Animations/Animation.cpp
@@ -277,6 +277,14 @@ WebIDL::ExceptionOr<void> Animation::set_playback_rate(double new_playback_rate)
 }
 
 // https://www.w3.org/TR/web-animations-1/#animation-play-state
+Bindings::AnimationPlayState Animation::play_state_for_bindings() const
+{
+    if (m_owning_element)
+        m_owning_element->document().update_style();
+
+    return play_state();
+}
+
 Bindings::AnimationPlayState Animation::play_state() const
 {
     // The play state of animation, animation, at a given moment is the state corresponding to the first matching
diff --git a/Libraries/LibWeb/Animations/Animation.h b/Libraries/LibWeb/Animations/Animation.h
index 277e888bfc5..d22829cba53 100644
--- a/Libraries/LibWeb/Animations/Animation.h
+++ b/Libraries/LibWeb/Animations/Animation.h
@@ -48,6 +48,7 @@ public:
     double playback_rate() const { return m_playback_rate; }
     WebIDL::ExceptionOr<void> set_playback_rate(double value);
 
+    Bindings::AnimationPlayState play_state_for_bindings() const;
     Bindings::AnimationPlayState play_state() const;
 
     bool is_relevant() const;
diff --git a/Libraries/LibWeb/Animations/Animation.idl b/Libraries/LibWeb/Animations/Animation.idl
index fc1579f636c..2b5f4eecac1 100644
--- a/Libraries/LibWeb/Animations/Animation.idl
+++ b/Libraries/LibWeb/Animations/Animation.idl
@@ -14,7 +14,7 @@ interface Animation : EventTarget {
     attribute double? startTime;
     attribute double? currentTime;
     attribute double playbackRate;
-    readonly attribute AnimationPlayState playState;
+    [ImplementedAs=play_state_for_bindings] readonly attribute AnimationPlayState playState;
     readonly attribute AnimationReplaceState replaceState;
     readonly attribute boolean pending;
     readonly attribute Promise<Animation> ready;
diff --git a/Tests/LibWeb/Text/expected/wpt-import/css/css-animations/CSSAnimation-canceling.tentative.txt b/Tests/LibWeb/Text/expected/wpt-import/css/css-animations/CSSAnimation-canceling.tentative.txt
new file mode 100644
index 00000000000..941701a0c8b
--- /dev/null
+++ b/Tests/LibWeb/Text/expected/wpt-import/css/css-animations/CSSAnimation-canceling.tentative.txt
@@ -0,0 +1,15 @@
+Harness status: OK
+
+Found 9 tests
+
+4 Pass
+5 Fail
+Fail	Animated style is cleared after canceling a running CSS animation
+Fail	Animated style is cleared after canceling a filling CSS animation
+Pass	After canceling an animation, it can still be seeked
+Fail	After canceling an animation, it can still be re-used
+Fail	After canceling an animation, updating animation properties doesn't make it live again
+Fail	After canceling an animation, updating animation-play-state doesn't make it live again
+Pass	Setting animation-name to 'none' cancels the animation
+Pass	Setting display:none on an element cancel its animations
+Pass	Setting display:none on an ancestor element cancels animations on descendants
\ No newline at end of file
diff --git a/Tests/LibWeb/Text/expected/wpt-import/css/css-animations/CSSAnimation-playState.tentative.txt b/Tests/LibWeb/Text/expected/wpt-import/css/css-animations/CSSAnimation-playState.tentative.txt
new file mode 100644
index 00000000000..c061881f71f
--- /dev/null
+++ b/Tests/LibWeb/Text/expected/wpt-import/css/css-animations/CSSAnimation-playState.tentative.txt
@@ -0,0 +1,10 @@
+Harness status: OK
+
+Found 5 tests
+
+5 Pass
+Pass	A new CSS animation is initially play-pending
+Pass	Animation returns correct playState when paused
+Pass	Animation.playState updates when paused by script
+Pass	Animation.playState updates when resumed by setting style
+Pass	Animation returns correct playState when canceled
\ No newline at end of file
diff --git a/Tests/LibWeb/Text/input/wpt-import/css/css-animations/CSSAnimation-canceling.tentative.html b/Tests/LibWeb/Text/input/wpt-import/css/css-animations/CSSAnimation-canceling.tentative.html
new file mode 100644
index 00000000000..5db420696d6
--- /dev/null
+++ b/Tests/LibWeb/Text/input/wpt-import/css/css-animations/CSSAnimation-canceling.tentative.html
@@ -0,0 +1,196 @@
+<!doctype html>
+<meta charset=utf-8>
+<title>Canceling a CSS animation</title>
+<!-- TODO: Add a more specific link for this once it is specified. -->
+<link rel="help" href="https://drafts.csswg.org/css-animations-2/">
+<script src="../../resources/testharness.js"></script>
+<script src="../../resources/testharnessreport.js"></script>
+<script src="support/testcommon.js"></script>
+<style>
+@keyframes translateAnim {
+  to { transform: translate(100px) }
+}
+@keyframes marginLeftAnim {
+  to { margin-left: 100px }
+}
+@keyframes marginLeftAnim100To200 {
+  from { margin-left: 100px }
+  to { margin-left: 200px }
+}
+</style>
+<div id="log"></div>
+<script>
+'use strict';
+
+promise_test(async t => {
+  const div = addDiv(t, { style: 'animation: translateAnim 100s' });
+  const animation = div.getAnimations()[0];
+
+  await animation.ready;
+
+  assert_not_equals(getComputedStyle(div).transform, 'none',
+                    'transform style is animated before canceling');
+  animation.cancel();
+  assert_equals(getComputedStyle(div).transform, 'none',
+                'transform style is no longer animated after canceling');
+}, 'Animated style is cleared after canceling a running CSS animation');
+
+promise_test(async t => {
+  const div = addDiv(t, { style: 'animation: translateAnim 100s forwards' });
+  const animation = div.getAnimations()[0];
+  animation.finish();
+
+  await animation.ready;
+
+  assert_not_equals(getComputedStyle(div).transform, 'none',
+                    'transform style is filling before canceling');
+  animation.cancel();
+  assert_equals(getComputedStyle(div).transform, 'none',
+                'fill style is cleared after canceling');
+}, 'Animated style is cleared after canceling a filling CSS animation');
+
+test(t => {
+  const div = addDiv(t, { style: 'animation: marginLeftAnim 100s linear' });
+  const animation = div.getAnimations()[0];
+  animation.cancel();
+
+  assert_equals(getComputedStyle(div).marginLeft, '0px',
+                'margin-left style is not animated after canceling');
+
+  animation.currentTime = 50 * 1000;
+  assert_equals(getComputedStyle(div).marginLeft, '50px',
+                'margin-left style is updated when canceled animation is'
+                + ' seeked');
+}, 'After canceling an animation, it can still be seeked');
+
+promise_test(async t => {
+  const div =
+    addDiv(t, { style: 'animation: marginLeftAnim100To200 100s linear' });
+  const animation = div.getAnimations()[0];
+
+  await animation.ready;
+
+  animation.cancel();
+  assert_equals(getComputedStyle(div).marginLeft, '0px',
+                'margin-left style is not animated after canceling');
+  animation.play();
+  assert_equals(getComputedStyle(div).marginLeft, '100px',
+                'margin-left style is animated after re-starting animation');
+
+  await animation.ready;
+
+  assert_equals(animation.playState, 'running',
+                'Animation succeeds in running after being re-started');
+}, 'After canceling an animation, it can still be re-used');
+
+test(t => {
+  const div =
+    addDiv(t, { style: 'animation: marginLeftAnim100To200 100s linear' });
+  const animation = div.getAnimations()[0];
+  animation.cancel();
+  assert_equals(getComputedStyle(div).marginLeft, '0px',
+                'margin-left style is not animated after canceling');
+
+  // Trigger a change to some animation properties and check that this
+  // doesn't cause the animation to become live again
+  div.style.animationDuration = '200s';
+  assert_equals(getComputedStyle(div).marginLeft, '0px',
+                'margin-left style is still not animated after updating'
+                + ' animation-duration');
+  assert_equals(animation.playState, 'idle',
+                'Animation is still idle after updating animation-duration');
+}, 'After canceling an animation, updating animation properties doesn\'t make'
+   + ' it live again');
+
+test(t => {
+  const div =
+    addDiv(t, { style: 'animation: marginLeftAnim100To200 100s linear' });
+  const animation = div.getAnimations()[0];
+  animation.cancel();
+  assert_equals(getComputedStyle(div).marginLeft, '0px',
+                'margin-left style is not animated after canceling');
+
+  // Make some changes to animation-play-state and check that the
+  // animation doesn't become live again. This is because it should be
+  // possible to cancel an animation from script such that all future
+  // changes to style are ignored.
+
+  // Redundant change
+  div.style.animationPlayState = 'running';
+  assert_equals(animation.playState, 'idle',
+                'Animation is still idle after a redundant change to'
+                + ' animation-play-state');
+
+  // Pause
+  div.style.animationPlayState = 'paused';
+  assert_equals(animation.playState, 'idle',
+                'Animation is still idle after setting'
+                + ' animation-play-state: paused');
+
+  // Play
+  div.style.animationPlayState = 'running';
+  assert_equals(animation.playState, 'idle',
+                'Animation is still idle after re-setting'
+                + ' animation-play-state: running');
+
+}, 'After canceling an animation, updating animation-play-state doesn\'t'
+   + ' make it live again');
+
+promise_test(async t => {
+  const div = addDiv(t, { style: 'animation: translateAnim 10s both' });
+  div.style.marginLeft = '0px';
+
+  const animation = div.getAnimations()[0];
+
+  await animation.ready;
+
+  assert_equals(animation.playState, 'running');
+
+  div.style.animationName = 'none';
+  flushComputedStyle(div);
+
+  await waitForFrame();
+
+  assert_equals(animation.playState, 'idle');
+  assert_equals(getComputedStyle(div).marginLeft, '0px');
+}, 'Setting animation-name to \'none\' cancels the animation');
+
+promise_test(async t => {
+  const div = addDiv(t, { style: 'animation: translateAnim 10s both' });
+  const animation = div.getAnimations()[0];
+
+  await animation.ready;
+
+  assert_equals(animation.playState, 'running');
+
+  div.style.display = 'none';
+
+  await waitForFrame();
+
+  assert_equals(animation.playState, 'idle');
+  assert_equals(getComputedStyle(div).marginLeft, '0px');
+}, 'Setting display:none on an element cancel its animations');
+
+promise_test(async t => {
+  const parentDiv = addDiv(t);
+  const childDiv  = document.createElement('div');
+  parentDiv.appendChild(childDiv);
+
+  childDiv.setAttribute('style', 'animation: translateAnim 10s both');
+  flushComputedStyle(childDiv);
+
+  const animation = childDiv.getAnimations()[0];
+
+  await animation.ready;
+
+  assert_equals(animation.playState, 'running');
+
+  parentDiv.style.display = 'none';
+  await waitForFrame();
+
+  assert_equals(animation.playState, 'idle');
+  assert_equals(getComputedStyle(childDiv).marginLeft, '0px');
+}, 'Setting display:none on an ancestor element cancels animations on ' +
+   'descendants');
+
+</script>
diff --git a/Tests/LibWeb/Text/input/wpt-import/css/css-animations/CSSAnimation-playState.tentative.html b/Tests/LibWeb/Text/input/wpt-import/css/css-animations/CSSAnimation-playState.tentative.html
new file mode 100644
index 00000000000..9033712b9c7
--- /dev/null
+++ b/Tests/LibWeb/Text/input/wpt-import/css/css-animations/CSSAnimation-playState.tentative.html
@@ -0,0 +1,55 @@
+<!doctype html>
+<meta charset=utf-8>
+<title>CSSAnimation.playState</title>
+<!-- TODO: Add a more specific link for this once it is specified. -->
+<link rel="help" href="https://drafts.csswg.org/css-animations-2/#cssanimation">
+<script src="../../resources/testharness.js"></script>
+<script src="../../resources/testharnessreport.js"></script>
+<script src="support/testcommon.js"></script>
+<style>
+@keyframes anim { }
+</style>
+<div id="log"></div>
+<script>
+'use strict';
+
+test(t => {
+  const div = addDiv(t, { 'style': 'animation: anim 100s' });
+  const animation = div.getAnimations()[0];
+  assert_true(animation.pending);
+  assert_equals(animation.playState, 'running');
+  assert_equals(animation.startTime, null);
+}, 'A new CSS animation is initially play-pending');
+
+test(t => {
+  const div = addDiv(t, { 'style': 'animation: anim 1000s paused' });
+  const animation = div.getAnimations()[0];
+  assert_equals(animation.playState, 'paused');
+}, 'Animation returns correct playState when paused');
+
+test(t => {
+  const div = addDiv(t, { 'style': 'animation: anim 1000s' });
+  const animation = div.getAnimations()[0];
+  animation.pause();
+  assert_equals(animation.playState, 'paused');
+}, 'Animation.playState updates when paused by script');
+
+test(t => {
+  const div = addDiv(t, { 'style': 'animation: anim 1000s paused' });
+  const animation = div.getAnimations()[0];
+  div.style.animationPlayState = 'running';
+
+  // This test also checks that calling playState flushes style
+  assert_equals(animation.playState, 'running',
+                'Animation.playState reports running after updating'
+                + ' animation-play-state (got: ' + animation.playState + ')');
+}, 'Animation.playState updates when resumed by setting style');
+
+test(t => {
+  const div = addDiv(t, { 'style': 'animation: anim 1000s' });
+  const animation = div.getAnimations()[0];
+  animation.cancel();
+  assert_equals(animation.playState, 'idle');
+}, 'Animation returns correct playState when canceled');
+
+</script>