28973 2015-07-20 12:48:48 +0000 <track> elements added with their text track already showing do not run the "time marches on" steps 2019-03-29 19:59:41 +0000 1 1 1 Unclassified WHATWG HTML unspecified PC All RESOLVED MOVED https://html.spec.whatwg.org/#text-track-model P2 normal Unsorted 1 philipj philip annevk contributor d mike contributor oldest_to_newest 122225 0 philipj 2015-07-20 12:48:48 +0000 https://html.spec.whatwg.org/#text-track-model "Whenever a text track that is in a media element's list of text tracks has its text track mode change value, the user agent must run the following steps for the media element:" This means that if a <track> element is first created and its text track's mode set to "showing" before appending it to the media element, these steps will not be run, and thus the "time marches on steps" steps which will cause any cues within to be shown will also not be run. This illustrates the problem: <video preload="auto"> <source src="video.mp4" type="video/mp4"> <source src="video.ogv" type="video/ogg"> </video> <script> var video = document.querySelector("video"); video.addEventListener("loadedmetadata", function() { video.currentTime = 1; }); video.addEventListener("seeked", function() { var bug = true; var track; if (bug) { var trackElement = document.createElement("track"); trackElement.kind = "subtitles"; track = trackElement.track; } else { track = video.addTextTrack("subtitles"); } track.addCue(new VTTCue(0, 10, "text")); track.mode = "showing"; if (bug) { video.appendChild(trackElement); } }); </script> The main point being that it's unfortunate that the order of setting track.mode and appending trackElement should matter at all. Of course, script-created tracks "should" be added with HTMLMediaElement.addTextTrack(), but it is still possible to add <track> elements and use their internal TextTracks instead. 122227 1 philipj 2015-07-20 12:50:37 +0000 *** Bug 28970 has been marked as a duplicate of this bug. *** 122229 2 philipj 2015-07-20 12:50:59 +0000 *** Bug 28971 has been marked as a duplicate of this bug. *** 122231 3 philipj 2015-07-20 12:51:08 +0000 *** Bug 28972 has been marked as a duplicate of this bug. *** 122232 4 philipj 2015-07-20 14:09:13 +0000 AFAICT, any later invocation of the "time marches on" steps would cause the cue to be rendered, which makes me think this is not a deliberate limitation of <track> elements. 129667 5 d 2019-03-29 19:59:41 +0000 https://github.com/whatwg/html/issues/4471