The recording is 60fps but WebView2 capture was a blind 100ms DispatcherTimer = 10Hz;
each captured web frame repeated ~6x into the file caps web animation at the capture
rate, not the page's (user: 'the animation appears to be too slow').
- New CaptureScheduler (Services/CaptureScheduler.cs): per-session dispatcher timer
that DROPS a tick while a capture is in flight (latest-wins, never queues) — the
guard that makes a higher cadence safe: concurrent full-HD PNG CapturePreviewAsync
calls (~10-30ms each, slow per WebView2Feedback#20) would stack CPU and publish
stale-after-fresh. Effective cadence = max(interval, capture duration).
- Cadence: SetCaptureInterval(33) on record/stream start, (200) idle — applied via
MainViewModel.Streaming.Operations.cs.
- De-throttle the hidden page: shared CoreWebView2Environment created BEFORE
EnsureCoreWebView2Async with --disable-backgrounding-occluded-windows
--disable-renderer-backgrounding --disable-features=CalculateNativeWinOcclusion.
Off-screen WebView2 is a hidden page when the host window is unfocused/covered and
Chromium then parks rAF and clamps timers to ~1s (WebView2Feedback#1172/#3070,
Chrome-88 timer-throttling blog).
- Telemetry: first 30 captures per session log elapsed ms (PNG encode + decode) to
startup.log — that decides whether ~30Hz stays or drops to ~20Hz; the FramePump
drops frames (never time-lapses, slice 10) if UI-thread GC churn starves it.
- ONE test: CaptureScheduler_Drops_Ticks_While_Capture_InFlight_And_Resumes
(deterministic TCS-driven, no WebView2 runtime). Suite 290/291 — sole failure the
pre-existing compositor pixel test.
- Docs same-commit: ai.md slice 11, MyMistakes.md, HANDOFF.
References: https://github.com/MicrosoftEdge/WebView2Feedback/issues/1172https://github.com/MicrosoftEdge/WebView2Feedback/issues/3070https://github.com/MicrosoftEdge/WebView2Feedback/issues/20https://developer.chrome.com/blog/timer-throttling-in-chrome-88
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