Create instance from worker (#2858)

Co-authored-by: Connor Fitzgerald <[email protected]>

CHANGELOG.md

@@ -58,6 +58,12 @@ Add the `"wgsl"` feature, to enable WGSL shaders in `wgpu-core` and `wgpu`. Enab
 - Bother to free the `hal::Api::CommandBuffer` when a `wgpu_core::command::CommandEncoder` is dropped. By @jimblandy in [#3069](https://github.com/gfx-rs/wgpu/pull/3069).
 - Fixed the mipmap example by adding the missing WRITE_TIMESTAMP_INSIDE_PASSES feature. By @Olaroll in [#3081](https://github.com/gfx-rs/wgpu/pull/3081).
 
+#### WebGPU
+- Use `log` instead of `println` in hello example by @JolifantoBambla in [#2858](https://github.com/gfx-rs/wgpu/pull/2858)
+
+### Examples
+- Log adapter info in hello example on wasm target by @JolifantoBambla in [#2858](https://github.com/gfx-rs/wgpu/pull/2858)
+
 ### Testing/Internal
 
 - Update the `minimum supported rust version` to 1.62
@@ -151,6 +157,9 @@ both `raw_window_handle::HasRawWindowHandle` and `raw_window_handle::HasRawDispl
 - Report vendor id for Mesa and Apple GPUs. By @i509VCB [#3036](https://github.com/gfx-rs/wgpu/pull/3036)
 - Report Apple M2 gpu as integrated. By @i509VCB [#3036](https://github.com/gfx-rs/wgpu/pull/3036)
 
+#### WebGPU
+- When called in a web worker, `Context::init()` now uses `web_sys::WorkerGlobalContext` to create a `wgpu::Instance` instead of trying to access the unavailable `web_sys::Window` by @JolifantoBambla in [#2858](https://github.com/gfx-rs/wgpu/pull/2858)
+
 ### Changes
 
 #### General
@@ -302,7 +311,6 @@ Added items to the public API
 - Update present_mode docs as most of them don't automatically fall back to Fifo anymore. by @Elabajaba in [#2855](https://github.com/gfx-rs/wgpu/pull/2855)
 
 #### Hal
-
 - Document safety requirements for `Adapter::from_external` in gles hal by @i509VCB in [#2863](https://github.com/gfx-rs/wgpu/pull/2863)
 - Make `AdapterContext` a publicly accessible type in the gles hal by @i509VCB in [#2870](https://github.com/gfx-rs/wgpu/pull/2870)
 

wgpu/Cargo.toml

@@ -286,7 +286,9 @@ web-sys = { version = "0.3.60", features = [
     "OffscreenCanvas",
     "ImageBitmap",
     "ImageBitmapRenderingContext",
-    "Window"
+    "Window",
+    "WorkerGlobalScope",
+    "WorkerNavigator"
 ] }
 wasm-bindgen = "0.2.83"
 js-sys = "0.3.60"

wgpu/examples/hello/main.rs

@@ -5,9 +5,9 @@ async fn run() {
         let instance = wgpu::Instance::new(wgpu::Backends::all());
         #[cfg(not(target_arch = "wasm32"))]
         {
-            println!("Available adapters:");
+            log::info!("Available adapters:");
             for a in instance.enumerate_adapters(wgpu::Backends::all()) {
-                println!("    {:?}", a.get_info())
+                log::info!("    {:?}", a.get_info())
             }
         }
         instance
@@ -16,8 +16,7 @@ async fn run() {
             .unwrap()
     };
 
-    #[cfg(not(target_arch = "wasm32"))]
-    println!("Selected adapter: {:?}", adapter.get_info())
+    log::info!("Selected adapter: {:?}", adapter.get_info())
 }
 
 fn main() {

wgpu/src/backend/web.rs

@@ -1007,6 +1007,21 @@ impl Context {
     }
 }
 
+// Represents the global object in the JavaScript context.
+// It can be cast to from `web_sys::global` and exposes two getters `window` and `worker` of which only one is defined depending on the caller's context.
+// When called from the UI thread only `window` is defined whereas `worker` is only defined within a web worker context.
+// See: https://github.com/rustwasm/gloo/blob/2c9e776701ecb90c53e62dec1abd19c2b70e47c7/crates/timers/src/callback.rs#L8-L40
+#[wasm_bindgen]
+extern "C" {
+    type Global;
+
+    #[wasm_bindgen(method, getter, js_name = Window)]
+    fn window(this: &Global) -> JsValue;
+
+    #[wasm_bindgen(method, getter, js_name = WorkerGlobalScope)]
+    fn worker(this: &Global) -> JsValue;
+}
+
 // The web doesn't provide any way to identify specific queue
 // submissions. But Clippy gets concerned if we pass around `()` as if
 // it were meaningful.
@@ -1051,7 +1066,20 @@ impl crate::Context for Context {
         MakeSendFuture<wasm_bindgen_futures::JsFuture, fn(JsFutureResult) -> Option<crate::Error>>;
 
     fn init(_backends: wgt::Backends) -> Self {
-        Context(web_sys::window().unwrap().navigator().gpu())
+        let global: Global = js_sys::global().unchecked_into();
+        let gpu = if !global.window().is_undefined() {
+            global.unchecked_into::<web_sys::Window>().navigator().gpu()
+        } else if !global.worker().is_undefined() {
+            global
+                .unchecked_into::<web_sys::WorkerGlobalScope>()
+                .navigator()
+                .gpu()
+        } else {
+            panic!(
+                "Accessing the GPU is only supported on the main thread or from a dedicated worker"
+            );
+        };
+        Context(gpu)
     }
 
     fn instance_create_surface(