Bug 192366

Summary: TextTrack added after video is loaded is not rendered when caption appearance is Automatic
Product: WebKit Reporter: Enrico Ghirardi <dev>
Component: MediaAssignee: Nobody <webkit-unassigned>
Status: NEW ---    
Severity: Normal CC: eric.carlson, jer.noble, webkit-bug-importer
Priority: P2 Keywords: InRadar
Version: WebKit Nightly Build   
Hardware: Mac   
OS: macOS 10.14   

Description Enrico Ghirardi 2018-12-04 11:01:19 PST
If captions display preference is set to automatic (MACaptionAppearanceGetDisplayType(kMACaptionAppearanceDomainUser) returns kMACaptionAppearanceDisplayTypeAutomatic) and a text track is added after the video has started playing, captions aren't shown.
To test:

1. Set caption display preferences to Automatic (MACaptionAppearanceSetDisplayType(kMACaptionAppearanceDomainUser, kMACaptionAppearanceDisplayTypeAutomatic);)
2. Visit https://iandevlin.com/html5/dynamic-track/
3. Press play on the video
4. Press Load Cues (which creates a TextTrack and the cues)
5. Captions aren't shown.
6. Reload the page
7. This time press Load Cues first
8. Press play on the video
9. Caption are now shown

Expected result:

If TextTrack is of kind "captions", the language is the same as navigator.language, and captions display preference is set to automatic, captions should be shown.
Comment 1 Radar WebKit Bug Importer 2018-12-05 10:48:22 PST
<rdar://problem/46492408>