Enable wasm-bindgen feature with target wasm32-unknown-emscripten

.github/workflows/platforms.yml

@@ -522,6 +522,34 @@ jobs:
         env:
           RUSTUP_TOOLCHAIN: nightly
 
+  # WebAssembly - Emscripten (WebAudio host)
+  wasm-emscripten:
+    runs-on: ubuntu-latest
+    env:
+      TARGET: wasm32-unknown-emscripten
+    steps:
+      - uses: actions/checkout@v5
+
+      - name: Install Rust MSRV (${{ env.MSRV_WASM }})
+        uses: dtolnay/rust-toolchain@master
+        with:
+          toolchain: ${{ env.MSRV_WASM }}
+          targets: ${{ env.TARGET }}
+
+      - name: Rust Cache
+        uses: Swatinem/rust-cache@v2
+        with:
+          key: wasm-emscripten
+
+      - name: Check examples (default features)
+        run: cargo +${{ env.MSRV_WASM }} check --examples --workspace --verbose --target ${{ env.TARGET }}
+
+      - name: Check examples (wasm-bindgen feature)
+        run: cargo +${{ env.MSRV_WASM }} check --examples --features wasm-bindgen --workspace --verbose --target ${{ env.TARGET }}
+
+      - name: Check all features
+        run: cargo +${{ env.MSRV_WASM }} check --workspace --all-features --verbose --target ${{ env.TARGET }}
+
   # WebAssembly - WASI Preview 1
   wasm-wasip1:
     runs-on: ubuntu-latest

.github/workflows/quality.yml

@@ -77,6 +77,12 @@ jobs:
             features: --features wasm-bindgen
             os: ubuntu-latest
 
+          # WASM - Emscripten (WebAudio host)
+          - target: wasm32-unknown-emscripten
+            name: WASM-emscripten
+            features: --features wasm-bindgen
+            os: ubuntu-latest
+
           # WASM - WASI
           - target: wasm32-wasip1
             name: WASI

CHANGELOG.md

@@ -27,6 +27,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - **ALSA**: Update `alsa` dependency to 0.12.
 - **Linux**: `realtime` can now promote threads without requiring `realtime-dbus`.
 - **PipeWire**: Set `node.rate` property so that `default.clock.allowed-rates` PipeWire config works.
+- **WebAudio**: the WebAudio host now works on `wasm32-unknown-emscripten` via [wasm-bindgen/Emscripten integration](https://github.com/wasm-bindgen/wasm-bindgen/issues/5237).
 
 ### Deprecated
 

Cargo.toml

@@ -199,7 +199,7 @@ objc2-avf-audio = { version = "0.3", default-features = false, features = [
   "AVAudioSessionTypes",
 ] }
 
-[target.'cfg(all(target_arch = "wasm32", target_os = "unknown"))'.dependencies]
+[target.'cfg(all(target_arch = "wasm32", any(target_os = "emscripten", target_os = "unknown")))'.dependencies]
 wasm-bindgen = { version = "0.2", optional = true }
 wasm-bindgen-futures = { version = "0.4", optional = true }
 futures-channel = { version = "0.3", optional = true }

README.md

@@ -52,7 +52,8 @@ The minimum Rust version (MSRV) and minimum operating system / runtime version b
 | PipeWire | Linux, BSD | 1.85 | PipeWire 0.3.53 |
 | PulseAudio | Linux, BSD | 1.88 | — |
 | WASAPI / ASIO | Windows | 1.85 | Windows 8 |
-| WASM (`wasm32-unknown`) | WebAssembly | 1.85 | — |
+| WASM (`wasm32-unknown-unknown`) | WebAssembly | 1.85 | — |
+| WASM (`wasm32-unknown-emscripten`) | WebAssembly | 1.85 | Emscripten 6.0.3, wasm-bindgen 0.2.127 |
 | WASM (`wasm32-wasip1`) | WebAssembly | 1.85 | — |
 | WASM (`audioworklet`) | WebAssembly | nightly | — |
 
@@ -70,7 +71,7 @@ The `audioworklet` backend additionally requires `-Zbuild-std` with atomics supp
 | `pulseaudio` | Linux, BSD | PulseAudio sound server backend. Requires `libpulse-dev` (Debian/Ubuntu) or `pulseaudio-libs-devel` (Fedora). |
 | `realtime` | Android, Linux, Windows | Raises the audio callback thread to real-time or high-priority scheduling for lower latency. On Linux, requires `CAP_SYS_NICE`, root, or an `rtprio` limit granted via `limits.conf` or systemd, unless `realtime-dbus` is also enabled. |
 | `realtime-dbus` | Linux | Uses `rtkit` via D-Bus for RT scheduling on Linux desktop systems. Implies `realtime` on all platforms. Requires `libdbus-1-dev` on Linux. |
-| `wasm-bindgen` | WebAssembly (`wasm32-unknown-unknown`) | Web Audio API backend for browser-based audio; required for any WebAssembly audio support. See the `webaudio` example. |
+| `wasm-bindgen` | WebAssembly (`wasm32-unknown-emscripten`, `wasm32-unknown-unknown`) | Web Audio API backend for browser-based audio; required for any WebAssembly audio support. See the `webaudio` example. |
 
 See the [beep example](examples/beep.rs) for selecting the backend at runtime.
 

src/host/mod.rs

@@ -78,7 +78,7 @@ pub(crate) mod wasapi;
 
 #[cfg(all(
     target_arch = "wasm32",
-    target_os = "unknown",
+    any(target_os = "emscripten", target_os = "unknown"),
     feature = "wasm-bindgen"
 ))]
 pub(crate) mod webaudio;
@@ -96,7 +96,7 @@ pub(crate) mod custom;
     target_os = "android",
     all(
         target_arch = "wasm32",
-        target_os = "unknown",
+        any(target_os = "emscripten", target_os = "unknown"),
         feature = "wasm-bindgen"
     ),
 )))]
@@ -246,7 +246,13 @@ pub(crate) use error_emit::try_emit_error;
     target_os = "netbsd",
     target_os = "windows",
     target_vendor = "apple",
-    feature = "audioworklet",
+    all(
+        target_arch = "wasm32",
+        target_os = "unknown",
+        feature = "wasm-bindgen",
+        feature = "audioworklet",
+        target_feature = "atomics"
+    ),
 ))]
 #[inline]
 pub(crate) fn frames_to_duration(
@@ -333,7 +339,7 @@ where
 /// <https://developer.mozilla.org/en-US/docs/Web/API/MediaDevices/getUserMedia#exceptions>
 #[cfg(all(
     target_arch = "wasm32",
-    target_os = "unknown",
+    any(target_os = "emscripten", target_os = "unknown"),
     feature = "wasm-bindgen"
 ))]
 pub(crate) fn get_user_media_error(js_err: &wasm_bindgen::JsValue) -> crate::Error {
@@ -366,7 +372,7 @@ pub(crate) fn get_user_media_error(js_err: &wasm_bindgen::JsValue) -> crate::Err
 /// <https://developer.mozilla.org/en-US/docs/Web/API/MediaDevices/getUserMedia>
 #[cfg(all(
     target_arch = "wasm32",
-    target_os = "unknown",
+    any(target_os = "emscripten", target_os = "unknown"),
     feature = "wasm-bindgen"
 ))]
 pub(crate) async fn request_microphone() -> Result<web_sys::MediaStream, wasm_bindgen::JsValue> {
@@ -387,7 +393,7 @@ pub(crate) async fn request_microphone() -> Result<web_sys::MediaStream, wasm_bi
 /// microphone is actually present without asking for permission first via getUserMedia().
 #[cfg(all(
     target_arch = "wasm32",
-    target_os = "unknown",
+    any(target_os = "emscripten", target_os = "unknown"),
     feature = "wasm-bindgen"
 ))]
 pub(crate) fn is_get_user_media_available() -> bool {
@@ -398,7 +404,7 @@ pub(crate) fn is_get_user_media_available() -> bool {
 /// browser's capture indicator. Dropping a WebAudio graph alone does not do this.
 #[cfg(all(
     target_arch = "wasm32",
-    target_os = "unknown",
+    any(target_os = "emscripten", target_os = "unknown"),
     feature = "wasm-bindgen"
 ))]
 pub(crate) fn stop_tracks(media_stream: &web_sys::MediaStream) {

src/host/webaudio/mod.rs

@@ -395,7 +395,7 @@ impl DeviceTrait for Device {
                 #[cfg(target_feature = "atomics")]
                 let current_time_bits_cb = current_time_bits.clone();
 
-                let on_audio_process = Closure::wrap(Box::new(move |event: AudioProcessingEvent| {
+                let on_audio_process_fn = Box::new(move |event: AudioProcessingEvent| {
                     let now = ctx_cb.current_time();
                     #[cfg(target_feature = "atomics")]
                     current_time_bits_cb.store(now.to_bits(), Ordering::Relaxed);
@@ -456,8 +456,8 @@ impl DeviceTrait for Device {
                             ),
                         ),
                     }
-                })
-                    as Box<dyn FnMut(AudioProcessingEvent)>);
+                });
+                let on_audio_process = Closure::wrap(on_audio_process_fn);
 
                 processor.set_onaudioprocess(Some(on_audio_process.as_ref().unchecked_ref()));
 
@@ -876,7 +876,7 @@ impl DeviceTrait for Device {
 
                     // Keep track of when the next buffer worth of samples should be played.
                     *time_handle.write().unwrap() = time_at_start_of_buffer + buffer_time_step_secs;
-                }) as Box<dyn FnMut()>));
+                })));
 
             on_ended_closures.push(on_ended_closure);
         }
@@ -1082,7 +1082,7 @@ impl DeviceTrait for Device {
                     js_sys::Float32Array::new(&temporary_channel_array)
                 };
 
-                let on_audio_process = Closure::wrap(Box::new(move |event: AudioProcessingEvent| {
+                let on_audio_process_fn = Box::new(move |event: AudioProcessingEvent| {
                     let now = ctx_cb.current_time();
                     #[cfg(target_feature = "atomics")]
                     current_time_bits_cb.store(now.to_bits(), Ordering::Relaxed);
@@ -1219,8 +1219,8 @@ impl DeviceTrait for Device {
                             return;
                         }
                     }
-                })
-                    as Box<dyn FnMut(AudioProcessingEvent)>);
+                });
+                let on_audio_process = Closure::wrap(on_audio_process_fn);
 
                 processor.set_onaudioprocess(Some(on_audio_process.as_ref().unchecked_ref()));
 

src/lib.rs

@@ -198,19 +198,19 @@
 // Extern crate declarations with `#[macro_use]` must unfortunately be at crate root.
 #[cfg(all(
     target_arch = "wasm32",
-    target_os = "unknown",
+    any(target_os = "emscripten", target_os = "unknown"),
     feature = "wasm-bindgen"
 ))]
 extern crate js_sys;
 #[cfg(all(
     target_arch = "wasm32",
-    target_os = "unknown",
+    any(target_os = "emscripten", target_os = "unknown"),
     feature = "wasm-bindgen"
 ))]
 extern crate wasm_bindgen;
 #[cfg(all(
     target_arch = "wasm32",
-    target_os = "unknown",
+    any(target_os = "emscripten", target_os = "unknown"),
     feature = "wasm-bindgen"
 ))]
 extern crate web_sys;
@@ -226,7 +226,7 @@ pub use platform::{
 pub use sample_format::{FromSample, I24, Sample, SampleFormat, SizedSample, U24};
 #[cfg(all(
     target_arch = "wasm32",
-    target_os = "unknown",
+    any(target_os = "emscripten", target_os = "unknown"),
     feature = "wasm-bindgen"
 ))]
 use wasm_bindgen::prelude::*;
@@ -426,7 +426,7 @@ pub enum BufferSize {
 
 #[cfg(all(
     target_arch = "wasm32",
-    target_os = "unknown",
+    any(target_os = "emscripten", target_os = "unknown"),
     feature = "wasm-bindgen"
 ))]
 impl wasm_bindgen::describe::WasmDescribe for BufferSize {
@@ -437,7 +437,7 @@ impl wasm_bindgen::describe::WasmDescribe for BufferSize {
 
 #[cfg(all(
     target_arch = "wasm32",
-    target_os = "unknown",
+    any(target_os = "emscripten", target_os = "unknown"),
     feature = "wasm-bindgen"
 ))]
 impl wasm_bindgen::convert::IntoWasmAbi for BufferSize {
@@ -454,7 +454,7 @@ impl wasm_bindgen::convert::IntoWasmAbi for BufferSize {
 
 #[cfg(all(
     target_arch = "wasm32",
-    target_os = "unknown",
+    any(target_os = "emscripten", target_os = "unknown"),
     feature = "wasm-bindgen"
 ))]
 impl wasm_bindgen::convert::FromWasmAbi for BufferSize {
@@ -476,7 +476,7 @@ impl wasm_bindgen::convert::FromWasmAbi for BufferSize {
 #[cfg_attr(
     all(
         target_arch = "wasm32",
-        target_os = "unknown",
+        any(target_os = "emscripten", target_os = "unknown"),
         feature = "wasm-bindgen"
     ),
     wasm_bindgen

src/platform/mod.rs

@@ -924,18 +924,22 @@ mod platform_impl {
 
 #[cfg(all(
     target_arch = "wasm32",
-    target_os = "unknown",
+    any(target_os = "emscripten", target_os = "unknown"),
     feature = "wasm-bindgen"
 ))]
 mod platform_impl {
-    #[cfg(all(feature = "audioworklet", target_feature = "atomics"))]
+    #[cfg(all(
+        target_os = "unknown",
+        feature = "audioworklet",
+        target_feature = "atomics"
+    ))]
     use crate::host::audioworklet::Host as AudioWorkletHost;
     use crate::host::webaudio::Host as WebAudioHost;
     use crate::traits::HostTrait as _;
 
     impl_platform_host!(
         WebAudio => WebAudioHost,
-        #[cfg(all(feature = "audioworklet", target_feature = "atomics"))] AudioWorklet => AudioWorkletHost,
+        #[cfg(all(target_os = "unknown", feature = "audioworklet", target_feature = "atomics"))] AudioWorklet => AudioWorkletHost,
         #[cfg(feature = "custom")] Custom => super::CustomHost
     );
 
@@ -1004,7 +1008,7 @@ mod platform_impl {
     target_os = "android",
     all(
         target_arch = "wasm32",
-        target_os = "unknown",
+        any(target_os = "emscripten", target_os = "unknown"),
         feature = "wasm-bindgen"
     ),
 )))]

src/sample_format.rs

@@ -30,7 +30,7 @@ pub use dasp_sample::U24;
 pub use dasp_sample::{FromSample, Sample};
 #[cfg(all(
     target_arch = "wasm32",
-    target_os = "unknown",
+    any(target_os = "emscripten", target_os = "unknown"),
     feature = "wasm-bindgen"
 ))]
 use wasm_bindgen::prelude::*;
@@ -56,7 +56,7 @@ use wasm_bindgen::prelude::*;
 #[cfg_attr(
     all(
         target_arch = "wasm32",
-        target_os = "unknown",
+        any(target_os = "emscripten", target_os = "unknown"),
         feature = "wasm-bindgen"
     ),
     wasm_bindgen