example-runner-wgpu: fix remaining issues, and default to mouse shader, for wasm/WebGPU.

Author: eddyb

examples/runners/wgpu/src/graphics.rs

@@ -88,8 +88,10 @@ async fn run(
     window: Window,
     compiled_shader_modules: CompiledShaderModules,
 ) {
-    let backends =
-        wgpu::Backends::from_env().unwrap_or(wgpu::Backends::VULKAN | wgpu::Backends::METAL);
+    // FIXME(eddyb) should this just use `wgpu::Backends::PRIMARY`?
+    // (that also enables the DirectX 12 backend, not sure we want that one?)
+    let backends = wgpu::Backends::from_env()
+        .unwrap_or(wgpu::Backends::VULKAN | wgpu::Backends::METAL | wgpu::Backends::BROWSER_WEBGPU);
     let instance = wgpu::Instance::new(&wgpu::InstanceDescriptor {
         backends,
         ..Default::default()

examples/runners/wgpu/src/lib.rs

@@ -216,7 +216,8 @@ fn maybe_watch(
 #[command()]
 pub struct Options {
     /// which shader to run
-    #[arg(short, long, default_value = "sky")]
+    #[cfg_attr(not(target_arch = "wasm32"), arg(short, long, default_value = "sky"))]
+    #[cfg_attr(target_arch = "wasm32", arg(short, long, default_value = "mouse"))]
     shader: RustGPUShader,
 
     #[arg(long)]
@@ -230,22 +231,24 @@ pub struct Options {
 pub fn main(
     #[cfg(target_os = "android")] android_app: winit::platform::android::activity::AndroidApp,
 ) {
-    // Hack: spirv_builder builds into a custom directory if running under cargo, to not
-    // deadlock, and the default target directory if not. However, packages like `proc-macro2`
-    // have different configurations when being built here vs. when building
-    // rustc_codegen_spirv normally, so we *want* to build into a separate target directory, to
-    // not have to rebuild half the crate graph every time we run. So, pretend we're running
-    // under cargo by setting these environment variables.
-    unsafe {
-        std::env::set_var("OUT_DIR", env!("OUT_DIR"));
-        std::env::set_var("PROFILE", env!("PROFILE"));
-    }
-
     let mut options = Options::parse();
 
     #[cfg(not(any(target_os = "android", target_arch = "wasm32")))]
-    if options.shader == RustGPUShader::Compute {
-        return compute::start(&options);
+    {
+        // Hack: spirv_builder builds into a custom directory if running under cargo, to not
+        // deadlock, and the default target directory if not. However, packages like `proc-macro2`
+        // have different configurations when being built here vs. when building
+        // rustc_codegen_spirv normally, so we *want* to build into a separate target directory, to
+        // not have to rebuild half the crate graph every time we run. So, pretend we're running
+        // under cargo by setting these environment variables.
+        unsafe {
+            std::env::set_var("OUT_DIR", env!("OUT_DIR"));
+            std::env::set_var("PROFILE", env!("PROFILE"));
+        }
+
+        if options.shader == RustGPUShader::Compute {
+            return compute::start(&options);
+        }
     }
 
     // HACK(eddyb) force push constant emulation using (read-only) SSBOs, on