gallery/vendor/i-slint-renderer-skia/build.rs
Greg Pomerantz 93b27d724b Root-cause and fix the Mali scroll jank; strip jank-hunt instrumentation
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).
2026-10-28 18:23:50 -04:00

24 lines
1.3 KiB
Rust

// Copyright © SixtyFPS GmbH <info@slint.dev>
// SPDX-License-Identifier: GPL-3.0-only OR LicenseRef-Slint-Royalty-free-2.0 OR LicenseRef-Slint-Software-3.0
use cfg_aliases::cfg_aliases;
fn main() {
// Setup cfg aliases
cfg_aliases! {
skia_backend_opengl: { any(feature = "opengl", not(any(target_vendor = "apple", target_family = "windows", target_arch = "wasm32"))) },
skia_backend_wgpu: { any(feature = "wgpu-29", feature = "wgpu-30") },
skia_backend_software: { not(target_os = "android") },
skia_backend_softbuffer: { all(skia_backend_software, feature = "softbuffer") },
// Targets where wgpu and Skia both have their Vulkan backend compiled in.
// This only happens if wgpu has been enabled, and, on windows an mac only, the "vulkan"
// feature is enabled. On linux and other non-macos unixes, skia_wgpu_vulkan is true by
// default, and enabling "vulkan" feature would only serve to have it prioritized over
// opengl at runtime.
skia_wgpu_vulkan: { all(skia_backend_wgpu, any(all(target_family = "unix", not(target_vendor = "apple")), all(any(target_vendor = "apple", target_family = "windows"), feature = "vulkan"))) },
skia_windowed: { any(skia_backend_wgpu, skia_backend_opengl, skia_backend_softbuffer) },
}
println!("cargo:rustc-check-cfg=cfg(slint_nightly_test)");
}