- Require `line === 'auto'` in the auto-caption signature so a cue that
is deliberately placed (e.g. `line:0` for top-edge) is left alone even
if it is also `align:start position:0%`. YouTube auto-captions never
set `line`.
- For lazily-loaded language tracks, only detach the cuechange listener
after the cue list is actually populated, in case a cuechange fires
before cues load.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
YouTube auto-generated captions (downloaded via yt-dlp) stamp every cue
with `align:start position:0%`, which pins the caption text to the
bottom-left of the player and makes it hard to read. Properly-authored
VTT files have no cue settings and already render centered.
Detect that auto-caption signature and reset only those cues to the
browser's centered default (align:center / position:auto / line:auto).
This mutates the in-memory VTTCue objects the browser parsed; the .vtt
file on disk is never modified, and deliberately-positioned cues are
left untouched.
Wired via each <track>'s onLoad. Non-default language tracks are
`disabled` at load (no cues yet), so they are normalized lazily on the
first cuechange when the user selects them.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
