1548923 - [webvtt] update cue display immediately after adding or removing cue

Status: RESOLVED FIXED

(Core :: Audio/Video: Playback, defect, P2)

Description

[Alastor Wu [:alwu]]

According to the spec [1], we will run TimeMarchesOn everytime when we add or remove a cue.

However, we won't update the cue display correctly if the media hasn't start, the TimeMarchesOn will early return here [2]. It's not the spec said, we should update cue display no matter video starts or not.

[1]
https://html.spec.whatwg.org/multipage/media.html#playing-the-media-resource:time-marches-on-2
https://html.spec.whatwg.org/multipage/media.html#playing-the-media-resource:time-marches-on-3

[2] https://searchfox.org/mozilla-central/rev/b4e790d05f5a146d186c238bac5601a553581d23/dom/html/TextTrackManager.cpp#634

Comment 1

[Alastor Wu [:alwu]]

Attachment: Bug 1548923 - part1 : abort 'TimeMarchesOn' algorithm during seeking.

According to the spec [1], we will run TimeMarchesOn everytime when we add or remove a cue. However, the spec didn't mention that we need to abort the algorithm steps if media hasn't started.

We should complete the TimeMarchesOn in order to update cue display after adding or removing a cue, no matter video starts or not.

[1]
https://html.spec.whatwg.org/multipage/media.html#playing-the-media-resource:time-marches-on-2
https://html.spec.whatwg.org/multipage/media.html#playing-the-media-resource:time-marches-on-3

Comment 2

[Alastor Wu [:alwu]]

Attachment: Bug 1548923 - part3 : add test 'test_webvtt_update_display_after_adding_or_removing_cue.html'.

Comment 3

[Alastor Wu [:alwu]]

Attachment: Bug 1548923 - part2 : reset cues' active flag when media element's ready state becomes 'HAVE_NOTHING'

According to the spec [1], whenever the media element's readyState is changed back to HAVE_NOTHING, we have to reset all cues' active flag and update cue display in order to hide them.

It also means that we should not set any cue's flag when media element's readyState is HAVE_NOTHING, so we should abort the TimeMarchesOn in this situation.

[1] https://html.spec.whatwg.org/multipage/media.html#text-track-cue-active-flag

Comment 4

[Alastor Wu [:alwu]]

Attachment: Bug 1548923 - part4 : prevent run `TimeMarchesOn` before media has any data.

In patch2, whenever the media element's readyState is changed back to HAVE_NOTHING, we would reset all cues' active flag and update cue display in order to hide them.

It also means that we should not set any cue's flag when media element's readyState is HAVE_NOTHING, so we should abort the TimeMarchesOn in this situation.

Comment 5

[Alastor Wu [:alwu]]

Attachment: Bug 1548923 - part5 : run `TimeMarchesOn` in correct order

To change code order in order to follow the spec's steps order.

Comment 6

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/667010d35e34
part1 : abort 'TimeMarchesOn' algorithm during seeking. r=jya
https://hg.mozilla.org/integration/autoland/rev/894e0713977b
part2 : reset cues' active flag when media element's ready state becomes 'HAVE_NOTHING' r=jya
https://hg.mozilla.org/integration/autoland/rev/1a3bb9e678fe
part3 : add test 'test_webvtt_update_display_after_adding_or_removing_cue.html'. r=jya
https://hg.mozilla.org/integration/autoland/rev/c64974ef15b2
part4 : prevent run `TimeMarchesOn` before media has any data. r=jya
https://hg.mozilla.org/integration/autoland/rev/005917cd9f36
part5 : run `TimeMarchesOn` in correct order r=jya

Comment 7

[Narcis Beleuzu [:NarcisB]]

https://hg.mozilla.org/mozilla-central/rev/667010d35e34
https://hg.mozilla.org/mozilla-central/rev/894e0713977b
https://hg.mozilla.org/mozilla-central/rev/1a3bb9e678fe
https://hg.mozilla.org/mozilla-central/rev/c64974ef15b2
https://hg.mozilla.org/mozilla-central/rev/005917cd9f36