Fix assorted issues with WebGL (gfx-rs#7448)

* Fix validation error when configuring the surface on WebGL

* Remove unneeded `webgl` feature

* Fix compilation of the `noop` backend on `wasm32`

* Prevent `webgpu` examples from incorrectly falling back to WebGL

* Reduce dependency set when building wasm examples

* Fix various warnings

Author: cwfitzgerald

Cargo.toml

@@ -68,7 +68,6 @@ wgpu = { version = "24.0.0", path = "./wgpu", default-features = false, features
     "dx12",
     "metal",
     "static-dxc",
-    "webgl",
     "noop",       # This should be removed if we ever have non-test crates that depend on wgpu
 ] }
 wgpu-core = { version = "24.0.0", path = "./wgpu-core" }

examples/features/Cargo.toml

@@ -44,7 +44,6 @@ obj.workspace = true
 png.workspace = true
 pollster.workspace = true
 web-time.workspace = true
-wgpu.workspace = true
 wgpu-types = { workspace = true, features = [
     "trace", # TODO(#5974): this should be a dep on wgpu/trace and not wgpu-types at all
 ] }
@@ -55,13 +54,15 @@ wgpu-test.workspace = true
 
 [target.'cfg(not(target_arch = "wasm32"))'.dependencies]
 env_logger.workspace = true
+wgpu.workspace = true
 
 [target.'cfg(target_arch = "wasm32")'.dependencies]
 console_error_panic_hook.workspace = true
 console_log.workspace = true
 fern.workspace = true
 wasm-bindgen.workspace = true
 wasm-bindgen-futures.workspace = true
+wgpu = { path = "../../wgpu", default-features = false, features = ["wgsl"] }
 # We need these features in the framework examples and tests
 web-sys = { workspace = true, features = [
     "Location",

wgpu-core/src/conv.rs

@@ -27,10 +27,7 @@ pub fn is_valid_copy_dst_texture_format(
     }
 }
 
-#[cfg_attr(
-    any(not(target_arch = "wasm32"), target_os = "emscripten"),
-    allow(unused)
-)]
+#[cfg_attr(any(not(webgl)), expect(unused))]
 pub fn is_valid_external_image_copy_dst_texture_format(format: wgt::TextureFormat) -> bool {
     use wgt::TextureFormat as Tf;
     match format {

wgpu-core/src/device/global.rs

@@ -1880,6 +1880,11 @@ impl Global {
                     Ok(wgt::PollStatus::Poll) => {
                         unreachable!("Cannot get a Poll result from a Wait action.")
                     }
+                    Err(WaitIdleError::Timeout) if cfg!(target_arch = "wasm32") => {
+                        // On wasm, you cannot actually successfully wait for the surface.
+                        // However WebGL does not actually require you do this, so ignoring
+                        // the failure is totally fine. See https://github.com/gfx-rs/wgpu/issues/7363
+                    }
                     Err(e) => {
                         break 'error e.into();
                     }

wgpu/Cargo.toml

@@ -76,7 +76,7 @@ webgl = ["wgpu-core/webgl", "dep:wgpu-hal", "dep:smallvec"]
 ## but performs no computation.
 ## Because it lacks basic functionality, it is only actually used if explicitly enabled
 ## through `NoopBackendOptions`.
-noop = ["wgpu-core/noop"]
+noop = ["wgpu-core/noop", "dep:wgpu-hal", "dep:smallvec"]
 
 #! **Note:** In the documentation, if you see that an item depends on a backend,
 #! it means that the item is only available when that backend is enabled _and_ the backend

wgpu/src/api/queue.rs

@@ -27,14 +27,7 @@ crate::cmp::impl_eq_ord_hash_proxy!(Queue => .inner);
 /// There is no analogue in the WebGPU specification.
 #[derive(Debug, Clone)]
 pub struct SubmissionIndex {
-    #[cfg_attr(
-        all(
-            target_arch = "wasm32",
-            not(target_os = "emscripten"),
-            not(feature = "webgl"),
-        ),
-        expect(dead_code)
-    )]
+    #[cfg_attr(not(wgpu_core), expect(dead_code))]
     pub(crate) index: u64,
 }
 #[cfg(send_sync)]

wgpu/src/backend/wgpu_core.rs

@@ -399,10 +399,7 @@ fn map_texture_copy_view(
     }
 }
 
-#[cfg_attr(
-    any(not(target_arch = "wasm32"), target_os = "emscripten"),
-    expect(unused)
-)]
+#[cfg_attr(not(webgl), expect(unused))]
 fn map_texture_tagged_copy_view(
     view: crate::CopyExternalImageDestInfo<&api::Texture>,
 ) -> wgc::command::CopyExternalImageDestInfo {
@@ -1815,13 +1812,17 @@ impl dispatch::QueueInterface for CoreQueue {
         }
     }
 
+    // This method needs to exist if either webgpu or webgl is enabled,
+    // but we only actually have an implementation if webgl is enabled.
     #[cfg(any(webgpu, webgl))]
+    #[cfg_attr(not(webgl), expect(unused_variables))]
     fn copy_external_image_to_texture(
         &self,
         source: &crate::CopyExternalImageSourceInfo,
         dest: crate::CopyExternalImageDestInfo<&crate::api::Texture>,
         size: crate::Extent3d,
     ) {
+        #[cfg(webgl)]
         match self.context.0.queue_copy_external_image_to_texture(
             self.id,
             source,

xtask/src/run_wasm.rs

@@ -32,7 +32,7 @@ pub(crate) fn run_wasm(shell: Shell, mut args: Arguments) -> anyhow::Result<()>
 
     xshell::cmd!(
         shell,
-        "cargo build --target wasm32-unknown-unknown --bin wgpu-examples --no-default-features --features webgpu {release_flag...}"
+        "cargo build --target wasm32-unknown-unknown -p wgpu-examples --no-default-features --features webgpu {release_flag...}"
     )
     .args(&cargo_args)
     .quiet()
@@ -53,7 +53,7 @@ pub(crate) fn run_wasm(shell: Shell, mut args: Arguments) -> anyhow::Result<()>
 
     xshell::cmd!(
         shell,
-        "cargo build --target wasm32-unknown-unknown --bin wgpu-examples --no-default-features --features webgl {release_flag...}"
+        "cargo build --target wasm32-unknown-unknown -p wgpu-examples --no-default-features --features webgl {release_flag...}"
     )
     .args(&cargo_args)
     .quiet()