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c370e2e1e5
CPU profile (Apr 2026, real-user scroll on 11k-line session) showed three hot loops in the per-frame render path: Output.get() per-frame walk: 24% total └─ sliceAnsi(line, from, to) per write: 18% total stringWidth(line) chain (cached + JS): 14% total All three were re-doing identical work every frame: same string → same clipped slice → same width. Fixes: 1. Memoize stringWidth (8k-entry LRU) for non-ASCII strings; ASCII fast-path skips the cache (inline scan beats Map.get for short ASCII, the >90% case). String.charCodeAt scan up to 64 chars is cheaper than the regex fallback. 2. Memoize wrapText (4k-entry LRU keyed by maxWidth|wrapType|text) — wrapAnsi is pure and the same content reflows identically every frame. 3. Memoize sliceAnsi (4k-entry LRU keyed by start|end|str) for the end-defined hot path used by Output.get(). 4. Skip the slice entirely in Output.get() when the line already fits the clip box (startsBefore=false && endsAfter=false). Most transcript lines never exceed their container width, and tokenizing them just to slice (line, 0, width) was pure overhead. This single fast-path drops sliceAnsi from 18% → ~0% in the profile. Also tighten virtualization constants (MAX_MOUNTED 260→120, OVERSCAN 40→20, SLIDE_STEP 25→12) and cap historical-message render at 800 chars / 16 lines via HISTORY_RENDER_MAX_*; messages inside the FULL_RENDER_TAIL_ITEMS window still render in full so reading-zone behavior is unchanged. Validation, real-user CPU profile, page-up scroll on 11k-line session: Output.get() self-time: 24% → 0.3% sliceAnsi total: 18% → not in top 25 stringWidth family: 14% → ~3% idle: 60.7% → 77.3% Frame timings (synthetic page-up profile harness): dur p95: ~10ms → 4.87ms dur p99: 25ms+ → 12.80ms yoga p99: ~20ms → 1.87ms The remaining CPU in the profile is Yoga layoutNode + React commit, which is the irreducible work for this UI tree size. |
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| .. | ||
| src | ||
| ambient.d.ts | ||
| index.d.ts | ||
| index.js | ||
| package-lock.json | ||
| package.json | ||
| text-input.d.ts | ||
| text-input.js | ||