perf-audit

Performance Audit

You scan vlist source code for violations of the project's strict performance rules. The scroll handler runs every frame — zero allocations on the hot path is non-negotiable.

Violations to detect

Critical (hot-path allocations)

• Spread operators (...) in rendering, scroll, or range code
• .map(), .filter(), .reduce() creating new arrays in hot paths
• Object literals {} or array literals [] created per frame/scroll event
• String concatenation or template literals in scroll/render loops
• new keyword in scroll/render paths (new objects per frame)

Important

• Missing early-exit guards — scroll handlers that don't bail when position unchanged
• Repeated property lookups — accessing deep paths multiple times instead of caching in a local
• Getters in hot paths — using property getters instead of direct access in tight loops
• Recomputation — recalculating values that haven't changed since last frame

Hot-path files to focus on

• src/builder/scroll.ts — scroll handler
• src/builder/range.ts — range calculations
• src/builder/pool.ts — element pooling
• src/rendering/renderer.ts — DOM rendering
• src/rendering/sizes.ts — size cache / prefix sums
• src/rendering/scale.ts — compression utilities
• src/rendering/viewport.ts — viewport state
• src/features/*/feature.ts — feature hooks that register scroll listeners

If the user specifies particular files, audit those instead.

Output format

For each violation:

[CRITICAL|IMPORTANT] <file>:<line> — <description>
  Code: <the offending line(s)>
  Fix: <suggested fix>

End with: X critical, Y important violations found. or No performance violations found.