gallery/vendor/wgpu-hal-30.0.1/build.rs
Greg Pomerantz 2f4768f354 Fix 120Hz scroll jank end-to-end: render-ahead present + full-cache eviction off the UI thread
Three root causes, all fixed and verified on the Pixel 9 Pro:

1. Present phase (backend + renderer): VSYNC_LOCKED_RENDER defers the
   render to the vsync wake; RENDER_AHEAD presents the previous frame at
   the start of render() (phase = wake + ~1.1 ms) and holds the new
   frame one slot. Crash fix: a held wgpu frame must be PRESENTED, never
   merely dropped, before the next acquire (AlreadyAcquired panic at
   launch otherwise); discard_pending_frame presents too.

2. Full-res prefetch churn (src/lib.rs): the 8-slot full cache cycled
   through a ~20-cell viewport forever (137 decodes/20 s) and each
   eviction free()'d a 50 MB Vec on the UI thread (20-52 ms CPU spikes,
   ~7/s = the residual SLOWEV NonMain jank). Fix: 60 s tombstone
   cooldown on evicted paths (idle prefetch skips, urgent tap bypasses)
   + off-thread reaper for the freed blobs (insert: 21 ms -> 4 us).

3. (earlier) Skia final flush + Mailbox present mode (vendor, M3).

Instrumentation (all behind --features perf): OTHR/INVK/INVK_TAG/FLCK
lines for cross-thread closure timing and push-site tagging.

Warm measured swipe, 8580-file grid: cadence median 8.33 ms (exact
120 Hz), p99 15.5 ms, 5/552 gaps >16.7 ms (0.9%, max 28.3 ms, zero
>33 ms); PRES phase median ~994 us, zero late frames. Docs updated
(docs/BUGS/scroll-jank-120hz.md, full scorecard + line reference).

Also: vendored i-slint-core + wgpu-hal (vkshim interposition patch),
vkshim profiling tooling, backend made a non-optional dep, debuggable
flag for simpleperf (REMOVE before shipping).
2026-10-30 02:49:23 -04:00

37 lines
1.8 KiB
Rust

fn main() {
cfg_aliases::cfg_aliases! {
native: { not(target_arch = "wasm32") },
send_sync: { any(
not(target_arch = "wasm32"),
all(feature = "fragile-send-sync-non-atomic-wasm", not(target_feature = "atomics"))
) },
webgl: { all(target_arch = "wasm32", not(target_os = "emscripten"), gles) },
Emscripten: { all(target_os = "emscripten", gles) },
dx12: { all(target_os = "windows", feature = "dx12") },
gles: { all(feature = "gles") },
// Within the GL ES backend, use `std` and be Send + Sync only if we are using a target
// that, among the ones where the GL ES backend is supported, has `std`.
gles_with_std: { all(
feature = "gles",
any(
not(target_arch = "wasm32"),
// Accept wasm32-unknown-unknown, which uniquely has a stub `std`
all(target_vendor = "unknown", target_os = "unknown"),
// Accept wasm32-unknown-emscripten and similar, which has a real `std`
target_os = "emscripten"
)
) },
metal: { all(target_vendor = "apple", feature = "metal") },
vulkan: { all(not(target_arch = "wasm32"), feature = "vulkan") },
drm: { all(
feature = "drm",
any(target_os = "linux", target_os = "freebsd", target_os = "netbsd", target_os = "openbsd")
) },
any_backend: { any(dx12, metal, vulkan, gles) },
// ⚠️ Keep in sync with target.cfg() definition in Cargo.toml and cfg_alias in `wgpu` crate ⚠️
static_dxc: { all(target_os = "windows", feature = "static-dxc", not(target_arch = "aarch64"), target_env = "msvc") },
supports_64bit_atomics: { target_has_atomic = "64" },
supports_ptr_atomics: { target_has_atomic = "ptr" }
}
}