From 3918a09a4b92d7b8570951fb3329c7051e6f316e Mon Sep 17 00:00:00 2001
From: Benjamin Frye <fryeb@users.noreply.github.com>
Date: Fri, 13 Dec 2024 11:58:23 +1100
Subject: [PATCH] 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          | 11 +----------
 examples/src/hello_triangle/mod.rs |  2 +-
 wgpu/src/util/init.rs              | 16 ++++++++++++++++
 3 files changed, 18 insertions(+), 11 deletions(-)

diff --git a/examples/src/framework.rs b/examples/src/framework.rs
index 77eaf07712..9b7c4368e1 100644
--- a/examples/src/framework.rs
+++ b/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(
diff --git a/examples/src/hello_triangle/mod.rs b/examples/src/hello_triangle/mod.rs
index 7c82d49cf0..27903795aa 100644
--- a/examples/src/hello_triangle/mod.rs
+++ b/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
diff --git a/wgpu/src/util/init.rs b/wgpu/src/util/init.rs
index 87f787bcb8..b4ff99ef87 100644
--- a/wgpu/src/util/init.rs
+++ b/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.