Greg Pomerantz
93b27d724b
The 19-26 ms mid-scroll stalls (Mali-only, fixed content offsets) were the Skia renderer's final synchronous GrDirectContext::flush() blocking the UI thread on Mali driver back-pressure — proven by per-stage timestamps in the vendored renderer (stall frames: flush 19-24 ms, walk 1-3 ms, 1 binding re-eval, image imports 0.1 ms each). - vendor/i-slint-renderer-skia (pinned 1.18.1, [patch.crates-io]): remove that one flush. Redundant on the wgpu backend: the surface already calls flush_and_submit before queue.present, same Vulkan queue, in-order. Phone: 0 stalls across 4 runs (max 3.6-7.4 ms vs the 8.3 ms budget), display verified clean. - docs/BUGS/slint-skia-final-flush-jank.md: full evidence, prior art (slint-ui/slint#12030 closest), open question for a future upstream filing (not filed yet). - Profiling also retired the O(n)-walk theory: Slint 1.18 prunes the item walk to ~133-152 items; the windowed Flickable built on that theory was already reverted (ListView is smooth with the fix). - Strip all jank-hunt instrumentation: FR/SCR/TICK/APLYD/STG logging, stg markers, .gallery_* file knobs, jsamp thread sampler, DbgScroll programmatic scroll, nblog perf-file mirroring. Also fixes the 'launches into unstoppable fast scroll' bug: a leftover .gallery_cmd was re-read on every launch (file never deleted) and overrode user swipes — the hook is gone. - Keep: nblog (logd backpressure is real), zero-dimension decode guards, keep-alive (default-off). - HANDOFF: replace stale windowed-Flickable section with the actual root cause/fix; 15 unit tests pass. Verified on phone (aarch64, 8580 photos) and emulator (x86_64).
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