Thumbnail rendering fixes:
- Strip now tiles from each clip's true (unclamped) origin and draws only the
tiles intersecting the visible rect, so it scrolls correctly and shows the
right frames when a clip is scrolled partly off the left. Both render sites
(collapsed group + expanded track) share one draw_video_thumbnail_strip helper.
- On-clip strip no longer freezes on the first thumbnail: get_thumbnail_at now
returns the actual thumbnail timestamp and the GPU texture cache keys on it, so
tiles refresh as closer thumbnails finish generating.
- Hover preview derives content time from the clip's true origin too (matches the
strip when scrolled off-screen).
- insert_thumbnail keeps the cache sorted + deduped (fixes a latent unsorted
binary_search bug, and makes concurrent restore + resume race-safe).
Thumbnail persistence (mirrors waveform persistence):
- MediaKind::Thumbnail rows, keyed by thumbnail_media_id(clip_id) (clip id XOR a
sentinel). Each clip's thumbnails PNG-encoded into one opaque LBTN blob (editor
owns the format), snapshotted cheaply (Arc clones) and encoded off the UI thread.
- Save writes the packs (kept in place on re-save); load reads them into
LoadedProject.thumbnail_blobs; the editor decodes + inserts them on a background
thread, so reload shows thumbnails instantly with no re-decode (even if the
source video file is missing).
- Partial sets are persisted with a complete flag and RESUMED on load:
generate_keyframe_thumbnails takes a should_skip predicate so a save made
mid-generation continues from where it left off instead of redoing the work.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
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