Add support for canceling CSS transitions
This change adds support for canceling CSS transitions when a property
is no longer transitionable or when an element becomes styled with
display:none. Support for canceling and replacing CSS transitions when
the end value changes is still pending. This change also takes advantage
of updating the constellation message to fix a bug where transition
events could be sent for closed pipelines.
Fixes #15079.
diff --git a/css/css-transitions/transitioncancel-002.html b/css/css-transitions/transitioncancel-002.html
new file mode 100644
index 0000000..e62b17b
--- /dev/null
+++ b/css/css-transitions/transitioncancel-002.html
@@ -0,0 +1,46 @@
+<!DOCTYPE html>
+<html>
+<head>
+<meta charset="utf-8">
+<title>CSS Transitions Test: Removing transitioning property from transition-property triggers transitioncancel</title>
+<link rel="author" title="Martin Robinson" href="mailto:mrobinson@igalia.com">
+<meta name="assert" content="Removing transitioning property from transition-property
+causes transitioncancel.">
+<link rel="help" href="https://drafts.csswg.org/css-transitions-2/#event-dispatch">
+
+<script src="/resources/testharness.js" type="text/javascript"></script>
+<script src="/resources/testharnessreport.js" type="text/javascript"></script>
+<script src="./support/helper.js" type="text/javascript"></script>
+
+</head>
+<body>
+<div id="log"></div>
+
+<script>
+promise_test(async t => {
+ // Create element and prepare to trigger a transition on it.
+ const div = addDiv(t, {
+ style: 'transition: background-color 0.25s; background-color: red;',
+ });
+
+ // Attach event listeners
+ const eventWatcher = new EventWatcher(t, div, ['transitioncancel']);
+ div.addEventListener('transitionend', t.step_func((event) => {
+ assert_unreached('transitionend event should not be fired');
+ }));
+
+ // Trigger transition
+ getComputedStyle(div).backgroundColor;
+ div.style.backgroundColor = 'green';
+ getComputedStyle(div).backgroundColor;
+
+ // Remove the transitioning property from transition-property asynchronously.
+ await waitForFrame();
+ div.style.transitionProperty = 'none';
+
+ await eventWatcher.wait_for('transitioncancel');
+}, 'Removing a transitioning property from transition-property should trigger transitioncancel');
+</script>
+
+</body>
+</html>
