The boot refresh blocked the UI for up to 195ms per sync block with 10
large feeds (500 episodes × 10KB descriptions), causing noticeable freezes
when navigating to Feed during startup.
Root causes and fixes:
- getRSSItems matched items on the full XML (16ms/feed) AND fetchEpisodes
ran a separate getRSSChannel regex (20ms/feed) — a redundant 5MB scan.
Eliminated getRSSChannel; parseChannelCoverUrl now works on the full XML
directly (itunes:image appears before items, so the first match is the
channel cover).
- parseEpisodesIncremental ran getRSSItems (full-XML regex) + the first
25-item parse chunk before yielding. Added yieldToUI() after getRSSItems
so the renderer paints before parsing begins.
- Reduced PARSE_CHUNK_SIZE from 25 to 5 so each sync block between yields
is at most 5 × parseRSSItem (~5ms), not 25 × (~25ms).
- Added yieldToUI() before sortEpisodesReverseChronological in
fetchEpisodes and loadMoreEpisodesForFeed so the sort doesn't pile on
the last parse chunk.
- Added yieldToUI() after response.text() in fetchEpisodes so the renderer
gets a turn before any sync regex work begins.
Measured with 10 feeds × 500 episodes × 10KB descriptions (worst case):
max event-loop block 195ms → 53ms, total blocking 593ms → 292ms.
Michael Freno
6c99b96b12