perf(main): only redraw when state changed#428
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The diff renderer rebuilds every visible line on each draw, so the unconditional redraw every 100ms wastes CPU on idle and ships needless bytes over slow links. Track a needs_redraw flag set by input events, the update check, message expiry, persisted-session reloads, and in-flight PR work, and skip terminal.draw() when nothing changed. PR spinners keep animating because has_pending_pr_work() forces a redraw each tick while a forge fetch is in flight.
joaomendoncaa
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Jun 26, 2026
The diff renderer rebuilds every visible line on each draw, so the unconditional redraw every 100ms wastes CPU on idle and ships needless bytes over slow links. Track a needs_redraw flag set by input events, the update check, message expiry, persisted-session reloads, and in-flight PR work, and skip terminal.draw() when nothing changed. PR spinners keep animating because has_pending_pr_work() forces a redraw each tick while a forge fetch is in flight.
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Following up on the discussion in #394, this is one of the smaller perf
patches I mentioned, with no async/streaming involved.
The main loop currently calls
terminal.draw()every 100ms regardlessof whether anything changed. The diff renderer rebuilds every visible
line on each draw, so on large diffs this burns CPU while idle and
ships needless escape sequences over slow links.
This adds a
needs_redrawflag set by:event::read()so the manycontinuepaths in the key handler still trigger a redraw)
animating and results paint as soon as they arrive)
When none of those fire,
terminal.draw()is skipped entirely.clear_expired_message()andpoll_persisted_session_changes()nowreturn
boolto report whether they touched visible state. The newhas_pending_pr_work()helper just ORs the six PR rx slots.Tested locally on a ~6k-line diff over a slow ssh hop: idle CPU drops
to zero and ratatui no longer re-emits the cursor-line attrs every
100ms.