Create instance from worker

CHANGELOG.md

@@ -75,6 +75,9 @@ the same every time it is rendered, we now warn if it is missing.
 
 - Fix `astc_hdr` formats support by @jinleili in [#2971]](https://github.com/gfx-rs/wgpu/pull/2971)
 
+#### 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
@@ -95,7 +98,6 @@ the same every time it is rendered, we now warn if it is missing.
 - Made `StagingBelt::write_buffer()` check more thoroughly for reusable memory; by @kpreid in [#2906](https://github.com/gfx-rs/wgpu/pull/2906)
 
 ### Documentation
-
 - Expanded `StagingBelt` documentation by @kpreid in [#2905](https://github.com/gfx-rs/wgpu/pull/2905)
 
 ### Build Configuration
@@ -104,6 +106,9 @@ the same every time it is rendered, we now warn if it is missing.
   run-time validation in `wgpu-core`. By @jimblandy in
   [#2872](https://github.com/gfx-rs/wgpu/pull/2872).
 
+### Examples
+- Log adapter info in hello example on wasm target by @JolifantoBambla in [#2858](https://github.com/gfx-rs/wgpu/pull/2858)
+
 ## wgpu-0.13.2 (2022-07-13)
 
 ### Bug Fixes
@@ -145,10 +150,14 @@ the same every time it is rendered, we now warn if it is missing.
 - 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)
 
+### Changes
+
+#### Metal
+- Extract the generic code into `get_metal_layer` by @jinleili in [#2826](https://github.com/gfx-rs/wgpu/pull/2826)
+
 ## wgpu-0.13.1 (2022-07-02)
 
 ### Bug Fixes

wgpu/Cargo.toml

@@ -280,7 +280,9 @@ web-sys = { version = "0.3.58", features = [
     "OffscreenCanvas",
     "ImageBitmap",
     "ImageBitmapRenderingContext",
-    "Window"
+    "Window",
+    "WorkerGlobalScope",
+    "WorkerNavigator"
 ] }
 wasm-bindgen = "0.2.81"
 js-sys = "0.3.58"

wgpu/examples/hello/main.rs

@@ -16,6 +16,9 @@ async fn run() {
             .unwrap()
     };
 
+    #[cfg(target_arch = "wasm32")]
+    log::info!("{:?}", adapter.get_info());
+
     #[cfg(not(target_arch = "wasm32"))]
     println!("Selected adapter: {:?}", adapter.get_info())
 }

wgpu/src/backend/web.rs

@@ -972,6 +972,21 @@ 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.
@@ -1016,7 +1031,20 @@ 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(