Investigate UI frame jank (80ms max frame interval)

[ysdede]

Trace: Trace-20260213T014231.json (summary in trace_analysis_summary.json)

Evidence

• frames: effective_fps 59.4, max interval 80.1ms, janky_frames_gt_2x_avg = 6
• These spikes indicate periodic main-thread stalls affecting UI responsiveness.

Hypothesis

• Jank correlates with heavy per-frame drawing loops (waveform + debug visualizer) and DevTools protocol traffic.

Actions

• Re-run trace with DebugPanel closed vs open to isolate paint cost.
• Re-run with waveform disabled to quantify cost of Waveform rAF loop.
• Capture Performance -> Rendering stats to see Layout/Paint spikes and correlate with LayeredBufferVisualizer.

Acceptance

• Max frame interval < 33ms in 30s run.
• Janky frames <= 1 in same workload.

[ysdede]

Progress update: PR #191 includes jank-reduction changes in waveform/debug visualizers.

What landed:

• adaptive scheduling in Waveform (rAF only during visible recording; timeout otherwise),
• removed periodic style polling in Waveform (theme observer instead),
• adaptive draw/fetch intervals in LayeredBufferVisualizer based on recording + visibility.

Next step is a fresh 30s trace to measure max frame interval and janky frames against this issue acceptance criteria.

[ysdede]

From Feb 2026 trace. LayeredBufferVisualizer has replaced BufferVisualizer for the main surface, and page-visible gating has landed. Needs fresh Chrome trace on current master to see if 80ms frame spikes persist.