perf(tui2): cache transcript view rendering #8693
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The transcript viewport draws every frame. Ratatui's Line::render_ref does grapheme segmentation and span layout, so repeated redraws can burn CPU during streaming even when the visible transcript hasn't changed. Introduce TranscriptViewCache to reduce per-frame work: - WrappedTranscriptCache memoizes flattened+wrapped transcript lines per width, appends incrementally as new cells arrive, and rebuilds on width change, truncation (backtrack), or transcript replacement. - TranscriptRasterCache caches rasterized rows (Vec<Cell>) per line index and user-row styling; redraws copy cells instead of rerendering spans. The caches are width-scoped and store base transcript content only; selection highlighting and copy affordances are applied after drawing. User rows include the row-wide base style in the cached raster. Refactor transcript_render to expose append_wrapped_transcript_cell for incremental building and add a test that incremental append matches the full build. Add docs/tui2/performance-testing.md as a playbook for macOS sample profiles and hotspot greps. Expand transcript_view_cache tests to cover rebuild conditions, raster equivalence vs direct rendering, user-row caching, and eviction. Test: cargo test -p codex-tui2
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track palette_version in tui/tui2 so requery_default_colors bumps a counter clear transcript raster rows whenever palette_version changes document palette_version so callers know why the counter exists
tibo-openai
approved these changes
Jan 3, 2026
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The transcript viewport draws every frame. Ratatui's Line::render_ref does grapheme segmentation and span layout, so repeated redraws can burn CPU during streaming even when the visible transcript hasn't changed.
Introduce TranscriptViewCache to reduce per-frame work:
The caches are width-scoped and store base transcript content only; selection highlighting and copy affordances are applied after drawing. User rows include the row-wide base style in the cached raster.
Refactor transcript_render to expose append_wrapped_transcript_cell for incremental building and add a test that incremental append matches the full build.
Add docs/tui2/performance-testing.md as a playbook for macOS sample profiles and hotspot greps.
Expand transcript_view_cache tests to cover rebuild conditions, raster equivalence vs direct rendering, user-row caching, and eviction.
Test: cargo test -p codex-tui2