fix: Read environment variable configs in hello_triangle example (#6698)

* fix: Read environment variable configs in hello_triangle example

* refactor: Add util method for creating entire instance descriptor from env

* fix: Fix clippy error/warning about "unneeded `return` statement"

examples/src/framework.rs

@@ -268,16 +268,7 @@ impl ExampleContext {
     async fn init_async<E: Example>(surface: &mut SurfaceWrapper, window: Arc<Window>) -> Self {
         log::info!("Initializing wgpu...");
 
-        let backends = wgpu::util::backend_bits_from_env().unwrap_or_default();
-        let dx12_shader_compiler = wgpu::util::dx12_shader_compiler_from_env().unwrap_or_default();
-        let gles_minor_version = wgpu::util::gles_minor_version_from_env().unwrap_or_default();
-
-        let instance = wgpu::Instance::new(wgpu::InstanceDescriptor {
-            backends,
-            flags: wgpu::InstanceFlags::from_build_config().with_env(),
-            dx12_shader_compiler,
-            gles_minor_version,
-        });
+        let instance = wgpu::Instance::new(wgpu::util::instance_descriptor_from_env());
         surface.pre_adapter(&instance, window);
 
         let adapter = get_adapter_with_capabilities_or_from_env(

examples/src/hello_triangle/mod.rs

@@ -10,7 +10,7 @@ async fn run(event_loop: EventLoop<()>, window: Window) {
     size.width = size.width.max(1);
     size.height = size.height.max(1);
 
-    let instance = wgpu::Instance::default();
+    let instance = wgpu::Instance::new(wgpu::util::instance_descriptor_from_env());
 
     let surface = instance.create_surface(&window).unwrap();
     let adapter = instance

wgpu/src/util/init.rs

@@ -138,6 +138,22 @@ pub fn gles_minor_version_from_env() -> Option<wgt::Gles3MinorVersion> {
     )
 }
 
+/// Get an instance descriptor from the following environment variables
+/// - WGPU_BACKEND
+/// - WGPU_DEBUG
+/// - WGPU_VALIDATION
+/// - WGPU_DX12_COMPILER
+/// - WGPU_GLES_MINOR_VERSION
+/// If variables are missing, falls back to default or build config values
+pub fn instance_descriptor_from_env() -> wgt::InstanceDescriptor {
+    wgt::InstanceDescriptor {
+        backends: backend_bits_from_env().unwrap_or_default(),
+        flags: wgt::InstanceFlags::from_build_config().with_env(),
+        dx12_shader_compiler: dx12_shader_compiler_from_env().unwrap_or_default(),
+        gles_minor_version: gles_minor_version_from_env().unwrap_or_default(),
+    }
+}
+
 /// Determines whether the [`Backends::BROWSER_WEBGPU`] backend is supported.
 ///
 /// The result can only be true if this is called from the main thread or a dedicated worker.