Slint-on-Mali was conclusively janky at its base level (sltest: 0.33-0.83%
slot drops on a scene with no app logic); egui on the same phone measured
3-7x cleaner (egtest: 0.12%, same referee/scene).
Architecture (see HANDOFF §8.11-8.12):
- winit 0.30 ApplicationHandler on android-activity 0.6, raw EGL (ES3),
egui_glow::EguiGlow. winit 0.30 never delivers RedrawRequested on
Android → the frame driver is app-owned: World::tick runs every loop
iteration from about_to_wait (liveness), render when dirty or
animating, park ~8 ms (one vblank) at rest.
- Virtualized grid painter (3 cols, visible rows ±4), GPU-resident
textures, turbojpeg worker pool decoding off-thread.
- CRITICAL pixel-pipeline fix: RGB8→Vec<Color32> conversion happens on
the WORKER (egui 0.31's from_rgba_unmultiplied is O(n) per-pixel,
8-60 ms/2 MB on the UI thread → 9.57% drops + phone OOM crash).
UI thread only MOVES the vector into ColorImage.
- Fling: per-event EMA velocity (frame-based dies at slow touch sampling),
clamp 14000 px/s; decay exp(-7.42 dt).
- Painter::image uv is NORMALIZED (0..1) — a screen-space uv made every
cell a solid rectangle (the emulator's solid-color test images hid it).
- Memory caps for a personal phone: full cache 6 entries / 16 MP.
Verified on emulator: grid, scroll, fling, viewer, back-key. Phone
deploy: thumbnails render, 8580 files. Pending: user finger test +
fr_capture phone run (per-pixel fix expected to cut render cost
18.8 ms → <8.3 ms).
Deletes: vendor/ (instrumented Slint tree), shim/, build.rs, gputex,
vkshim, baseline60, main.slint — the Slint zero-jank campaign is
concluded in docs/BUGS/.
Greg Pomerantz
5a8284e7a9