Implement support for detecting when TTS is speaking.

src/backends/speech_dispatcher.rs

@@ -21,6 +21,7 @@ impl Backend for SpeechDispatcher {
             rate: true,
             pitch: true,
             volume: true,
+            is_speaking: false,
         }
     }
 
@@ -108,4 +109,8 @@ impl Backend for SpeechDispatcher {
         self.0.set_volume(volume as i32);
         Ok(())
     }
+
+    fn is_speaking(&self) -> Result<bool, Error> {
+        unimplemented!()
+    }
 }

src/backends/tolk.rs

@@ -22,6 +22,7 @@ impl Backend for Tolk {
             rate: false,
             pitch: false,
             volume: false,
+            is_speaking: false,
         }
     }
 
@@ -96,4 +97,8 @@ impl Backend for Tolk {
     fn set_volume(&mut self, _volume: f32) -> Result<(), Error> {
         unimplemented!();
     }
+
+    fn is_speaking(&self) -> Result<bool, Error> {
+        unimplemented!()
+    }
 }

src/backends/web.rs

@@ -28,6 +28,7 @@ impl Backend for Web {
             rate: true,
             pitch: true,
             volume: true,
+            is_speaking: true,
         }
     }
 
@@ -118,4 +119,16 @@ impl Backend for Web {
         self.volume = volume;
         Ok(())
     }
+
+    fn is_speaking(&self) -> Result<bool, Error> {
+        trace!("is_speaking()");
+        if let Some(window) = web_sys::window() {
+            match window.speech_synthesis() {
+                Ok(speech_synthesis) => Ok(speech_synthesis.speaking()),
+                Err(e) => Err(Error::JavaScriptError(e)),
+            }
+        } else {
+            Err(Error::NoneError)
+        }
+    }
 }

src/backends/winrt.rs

@@ -51,6 +51,7 @@ impl Backend for WinRT {
             rate: true,
             pitch: true,
             volume: true,
+            is_speaking: false,
         }
     }
 
@@ -136,4 +137,8 @@ impl Backend for WinRT {
         self.synth.options()?.set_audio_volume(volume.into())?;
         Ok(())
     }
+
+    fn is_speaking(&self) -> Result<bool, Error> {
+        unimplemented!()
+    }
 }

src/lib.rs

@@ -28,12 +28,17 @@ pub struct Features {
     pub rate: bool,
     pub pitch: bool,
     pub volume: bool,
+    pub is_speaking: bool,
 }
 
 #[derive(Debug, Error)]
 pub enum Error {
     #[error("IO error: {0}")]
     IO(#[from] std::io::Error),
+    #[error("Value not received")]
+    NoneError,
+    #[error("JavaScript error: [0])]")]
+    JavaScriptError(wasm_bindgen::JsValue),
     #[cfg(windows)]
     #[error("WinRT error")]
     WinRT(winrt::Error),
@@ -62,6 +67,7 @@ pub trait Backend {
     fn normal_volume(&self) -> f32;
     fn get_volume(&self) -> Result<f32, Error>;
     fn set_volume(&mut self, volume: f32) -> Result<(), Error>;
+    fn is_speaking(&self) -> Result<bool, Error>;
 }
 
 pub struct TTS(Box<dyn Backend>);
@@ -298,4 +304,16 @@ impl TTS {
             Err(Error::UnsupportedFeature)
         }
     }
+
+    /**
+     * Returns whether this speech synthesizer is speaking.
+     */
+    pub fn is_speaking(&self) -> Result<bool, Error> {
+        let Features { is_speaking, .. } = self.supported_features();
+        if is_speaking {
+            self.0.is_speaking()
+        } else {
+            Err(Error::UnsupportedFeature)
+        }
+    }
 }