Merge canonical main after the wgpu 30 upgrade

tests/draw_cost.rs

@@ -4,20 +4,19 @@
 //!
 //!     cargo test --release --test draw_cost -- --ignored --nocapture
 //!
-//! **Read the instruction count, not the clock.** Wall time here swings by 2x
-//! between runs of one binary on this machine -- more under `cargo test` than
-//! run directly -- while instructions retired are stable to 0.1%:
+//! Wall time is the wrong number to read for anything under a few percent --
+//! it varied by 2x between runs of one unchanged binary where instructions
+//! retired varied by 0.1%. Count those instead:
 //!
 //!     perf stat -e instructions:u target/release/.../draw_cost-* --ignored
 //!
-//! Measured that way on 2026-09-13, drawing each primitive through its own
-//! `PrimitiveRender` rather than a match in the renderer costs **6
-//! instructions per list drawn**, which is 0.1% of a frame at both 256 and
-//! 1024 layers. Recording one list into the pass costs wgpu ~5,400.
+//! That is how `PrimitiveRender` was measured against a match in the renderer:
+//! 6 instructions per list drawn, against the ~5,400 wgpu spends recording
+//! one.
 //!
-//! The instance is leaked on purpose. Dropping the last one makes the Vulkan
-//! loader unload Mesa's ICD, which faults when a thread that touched Vulkan
-//! exits -- and libtest runs every test on a spawned thread.
+//! The instance is leaked deliberately. A Vulkan loader may unload the driver
+//! when the last one drops, which can fault as a thread that used it exits --
+//! and every test runs on a spawned thread.
 
 use std::time::Instant;
 
@@ -30,20 +29,20 @@ use wgpu::{Color as GpuColor, *};
 
 const SIZE: u32 = 1024;
 const FRAMES: u32 = 200;
-/// Reported as the best of this many batches. The mean moves by 15% between
-/// runs on this machine, which is more than the thing being measured.
+/// Reported as the best of this many batches, since the mean moves by more
+/// than the thing being measured.
 const BATCHES: u32 = 8;
 
 fn gpu() -> Option<(Device, Queue)> {
-    // Probed rather than assumed: this machine's Vulkan device comes and goes,
-    // and GL is what is left when it is gone.
-    let all = Instance::new(&InstanceDescriptor::default());
+    // Probed rather than assumed: there may be no Vulkan adapter, and GL is
+    // what is left when there is not.
+    let all = Instance::new(InstanceDescriptor::new_without_display_handle());
     let instance = match pollster::block_on(all.request_adapter(&RequestAdapterOptions::default()))
     {
         Ok(_) => all,
-        Err(_) => Instance::new(&InstanceDescriptor {
+        Err(_) => Instance::new(InstanceDescriptor {
             backends: Backends::GL,
-            ..Default::default()
+            ..InstanceDescriptor::new_without_display_handle()
         }),
     };
     // Leaked rather than dropped: see the note at the top of the file.
@@ -58,6 +57,7 @@ fn config(format: TextureFormat) -> SurfaceConfiguration {
     SurfaceConfiguration {
         usage: TextureUsages::RENDER_ATTACHMENT,
         format,
+        color_space: SurfaceColorSpace::Auto,
         width: SIZE,
         height: SIZE,
         present_mode: PresentMode::Fifo,