Set "is currently stalled" before firing events #11959
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A test for this would be: <!DOCTYPE html>
<title>Media Loading State: the :buffering and :stalled pseudo-classes</title>
<link rel="help" href="https://drafts.csswg.org/selectors/#media-loading-state">
<script src="/resources/testharness.js"></script>
<script src="/resources/testharnessreport.js"></script>
<script src="/common/media.js"></script>
<body>
<video width="300" height="300" muted autoplay></video>
<script>
// The order of "is currently stalled" changing and events firing changed in
// https://github.com/whatwg/html/pull/11959. This test asserts that when
// the stalled event is fired, :stalled already matches.
async_test((t) => {
assert_implements(CSS.supports("selector(:stalled)"), ":stalled is not supported");
const video = document.querySelector("video");
// Send the first 100 kB and then stall "forever" (1 hour).
video.src = `/media/movie_300.webm?pipe=trickle(100000:d3600)&random=${Math.random()}`;
video.addEventListener("stalled", t.step_func_done(() => {
assert_true(video.matches(":stalled"), ":stalled matches in stalled event handler");
}));
}, "Test :stalled timing relative to stalled event");
// Note: it would be good to also test that :stalled doesn't match when the
// progress event is fired, but that would require resuming the loading
// again on demand and pipe=trickle doesn't support this.
</script>
</body>Safari fails this test. Unfortunately this test runs into the issues I described in web-platform-tests/interop#1003 (comment), that I haven't found anything that robustly fires the stalled event in all browsers. |
annevk
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Nov 27, 2025
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This makes much more sense. We should always change state before firing events. And changing the state and firing the event should happen in the same task.
In WebKit the event is queued and then the state is changed which would make it observable before the event is dispatched (as they happen in different tasks). That doesn't seem good either, but also doesn't explain why your test would fail which doesn't hit that scenario.
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Fixes #11958.
(See WHATWG Working Mode: Changes for more details.)
/media.html ( diff )