Testers report ~50 ms input-to-pixel while painting on Linux and macOS, and asked for a
per-stage breakdown. With PHOTOCRAFT_STROKE_TRACE=1 the app prints, per stroke, p50/p95 of
the frame interval, pointer moves per frame, the live stroke's render, the canvas refresh
(composite + upload), the UI build, eframe's CPU time (UI, tessellation, submission) and the
remaining vsync/swap-chain wait, with the GPU backend; =<file.csv> also appends every frame.
The last summary is in the control channel's perf.strokeTrace.
RTX 5090, Vulkan, 120 Hz: interval 8.33, cpu 2.2 (ui 0.9, stroke 0.8, canvas 0.4), wait 6.0 ms.
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