Merge remote-tracking branch 'upstream/master' into c-ffi

.github/workflows/release.yml

@@ -27,14 +27,26 @@ jobs:
         with:
           command: check
           args: --all-features --examples
+        if: ${{ runner.os != 'Linux' }}
+      - uses: actions-rs/cargo@v1
+        with:
+          command: check
+          args: --no-default-features --examples
+        if: ${{ runner.os == 'Linux' }}
       - uses: actions-rs/cargo@v1
         with:
           command: fmt
-          args: --all -- --check
+          args: --all --check
       - uses: actions-rs/clippy-check@v1
         with:
           token: ${{ secrets.GITHUB_TOKEN }}
           args: --all-features
+        if: ${{ runner.os != 'Linux' }}
+      - uses: actions-rs/clippy-check@v1
+        with:
+          token: ${{ secrets.GITHUB_TOKEN }}
+          args: --no-default-features
+        if: ${{ runner.os == 'Linux' }}
 
   check_web:
     name: Check Web
@@ -88,4 +100,4 @@ jobs:
           sudo apt-get update
           sudo apt-get install -y libspeechd-dev
           cargo login $CARGO_TOKEN
-          cargo publish
+          cargo publish --no-default-features

.github/workflows/test.yml

@@ -26,14 +26,26 @@ jobs:
         with:
           command: check
           args: --all-features --examples
+        if: ${{ runner.os != 'Linux' }}
+      - uses: actions-rs/cargo@v1
+        with:
+          command: check
+          args: --no-default-features --examples
+        if: ${{ runner.os == 'Linux' }}
       - uses: actions-rs/cargo@v1
         with:
           command: fmt
-          args: --all -- --check
+          args: --all --check
       - uses: actions-rs/clippy-check@v1
         with:
           token: ${{ secrets.GITHUB_TOKEN }}
           args: --all-features
+        if: ${{ runner.os != 'Linux' }}
+      - uses: actions-rs/clippy-check@v1
+        with:
+          token: ${{ secrets.GITHUB_TOKEN }}
+          args: --no-default-features
+        if: ${{ runner.os == 'Linux' }}
 
   check_web:
     name: Check Web
@@ -55,7 +67,7 @@ jobs:
       - uses: actions-rs/cargo@v1
         with:
           command: fmt
-          args: --all -- --check
+          args: --all --check
       - uses: actions-rs/clippy-check@v1
         with:
           token: ${{ secrets.GITHUB_TOKEN }}

Cargo.toml

@@ -1,19 +1,20 @@
 [package]
 name = "tts"
-version = "0.17.3"
+version = "0.23.0"
 authors = ["Nolan Darilek <nolan@thewordnerd.info>"]
 repository = "https://github.com/ndarilek/tts-rs"
 description = "High-level Text-To-Speech (TTS) interface"
 license = "MIT"
 exclude = ["*.cfg", "*.yml"]
-edition = "2018"
+edition = "2021"
 
 [lib]
 crate-type = ["lib", "cdylib", "staticlib"]
 
 [features]
-use_tolk = ["tolk"]
 ffi = ["cbindgen"]
+speech_dispatcher_0_10 = ["speech-dispatcher/0_10"]
+default = ["speech_dispatcher_0_10"]
 
 [dependencies]
 dyn-clonable = "0.9"
@@ -21,32 +22,35 @@ lazy_static = "1"
 libc = {version = "0.2", optional = true}
 log = "0.4"
 thiserror = "1"
+unic-langid = "0.9.0"
+serde = { version = "1.0", optional = true, features = ["derive"] }
 
 [dev-dependencies]
-env_logger = "0.8"
+env_logger = "0.9"
 
 [build-dependencies]
 cbindgen = {version = "0.18.0", optional = true}
 
 [target.'cfg(windows)'.dependencies]
 tolk = { version = "0.5", optional = true }
-windows = "0.9"
+windows = { version = "0.39", features = ["Foundation", "Foundation_Collections", "Media_Core", "Media_Playback", "Media_SpeechSynthesis", "Storage_Streams"] }
-
-[target.'cfg(windows)'.build-dependencies]
-windows = "0.9"
 
 [target.'cfg(target_os = "linux")'.dependencies]
-speech-dispatcher = "0.7"
+speech-dispatcher = { version = "0.13", default-features = false }
 
 [target.'cfg(any(target_os = "macos", target_os = "ios"))'.dependencies]
 cocoa-foundation = "0.1"
+core-foundation = "0.9"
 libc = "0.2"
 objc = { version = "0.2", features = ["exception"] }
 
 [target.wasm32-unknown-unknown.dependencies]
 wasm-bindgen = "0.2"
-web-sys = { version = "0.3", features = ["EventTarget", "SpeechSynthesis", "SpeechSynthesisErrorCode", "SpeechSynthesisErrorEvent", "SpeechSynthesisEvent", "SpeechSynthesisUtterance", "Window", ] }
+web-sys = { version = "0.3", features = ["EventTarget", "SpeechSynthesis", "SpeechSynthesisErrorCode", "SpeechSynthesisErrorEvent", "SpeechSynthesisEvent", "SpeechSynthesisUtterance", "SpeechSynthesisVoice", "Window", ] }
 
 [target.'cfg(target_os="android")'.dependencies]
 jni = "0.19"
-ndk-glue = "0.3"
+ndk-glue = "0.6"
+
+[package.metadata.docs.rs]
+no-default-features = true

build.rs

@@ -1,14 +1,4 @@
 fn main() {
-    #[cfg(windows)]
-    if std::env::var("TARGET").unwrap().contains("windows") {
-        windows::build!(
-            Windows::Foundation::{EventRegistrationToken, IAsyncOperation, TypedEventHandler},
-            Windows::Media::Core::MediaSource,
-            Windows::Media::Playback::{MediaPlaybackSession, MediaPlaybackState, MediaPlayer, MediaPlayerAudioCategory},
-            Windows::Media::SpeechSynthesis::{SpeechSynthesisStream, SpeechSynthesizer, SpeechSynthesizerOptions},
-            Windows::Storage::Streams::IRandomAccessStream,
-        );
-    }
     if std::env::var("TARGET").unwrap().contains("-apple") {
         println!("cargo:rustc-link-lib=framework=AVFoundation");
         if !std::env::var("CARGO_CFG_TARGET_OS")

examples/android/build.gradle

@@ -11,7 +11,7 @@ buildscript {
     dependencies {
         classpath "com.android.tools.build:gradle:4.1.1"
         classpath "org.jetbrains.kotlin:kotlin-gradle-plugin:$kotlin_version"
-        classpath "gradle.plugin.com.github.willir.rust:plugin:0.3.3"
+        classpath "gradle.plugin.com.github.willir.rust:plugin:0.3.4"
         // NOTE: Do not place your application dependencies here; they belong
         // in the individual module build.gradle files
     }

examples/android/cargo.toml

@@ -10,5 +10,5 @@ edition = "2018"
 crate-type = ["dylib"]
 
 [dependencies]
-ndk-glue = "0.2"
+ndk-glue = "0.6"
 tts = { path = "../.." }

examples/clone_drop.rs

@@ -0,0 +1,89 @@
+use std::io;
+
+#[cfg(target_os = "macos")]
+use cocoa_foundation::base::id;
+#[cfg(target_os = "macos")]
+use cocoa_foundation::foundation::NSRunLoop;
+#[cfg(target_os = "macos")]
+use objc::{msg_send, sel, sel_impl};
+
+use tts::*;
+
+fn main() -> Result<(), Error> {
+    env_logger::init();
+    let tts = Tts::default()?;
+    if Tts::screen_reader_available() {
+        println!("A screen reader is available on this platform.");
+    } else {
+        println!("No screen reader is available on this platform.");
+    }
+    let Features {
+        utterance_callbacks,
+        ..
+    } = tts.supported_features();
+    if utterance_callbacks {
+        tts.on_utterance_begin(Some(Box::new(|utterance| {
+            println!("Started speaking {:?}", utterance)
+        })))?;
+        tts.on_utterance_end(Some(Box::new(|utterance| {
+            println!("Finished speaking {:?}", utterance)
+        })))?;
+        tts.on_utterance_stop(Some(Box::new(|utterance| {
+            println!("Stopped speaking {:?}", utterance)
+        })))?;
+    }
+    let mut tts_clone = tts.clone();
+    drop(tts);
+    let Features { is_speaking, .. } = tts_clone.supported_features();
+    if is_speaking {
+        println!("Are we speaking? {}", tts_clone.is_speaking()?);
+    }
+    tts_clone.speak("Hello, world.", false)?;
+    let Features { rate, .. } = tts_clone.supported_features();
+    if rate {
+        let original_rate = tts_clone.get_rate()?;
+        tts_clone.speak(format!("Current rate: {}", original_rate), false)?;
+        tts_clone.set_rate(tts_clone.max_rate())?;
+        tts_clone.speak("This is very fast.", false)?;
+        tts_clone.set_rate(tts_clone.min_rate())?;
+        tts_clone.speak("This is very slow.", false)?;
+        tts_clone.set_rate(tts_clone.normal_rate())?;
+        tts_clone.speak("This is the normal rate.", false)?;
+        tts_clone.set_rate(original_rate)?;
+    }
+    let Features { pitch, .. } = tts_clone.supported_features();
+    if pitch {
+        let original_pitch = tts_clone.get_pitch()?;
+        tts_clone.set_pitch(tts_clone.max_pitch())?;
+        tts_clone.speak("This is high-pitch.", false)?;
+        tts_clone.set_pitch(tts_clone.min_pitch())?;
+        tts_clone.speak("This is low pitch.", false)?;
+        tts_clone.set_pitch(tts_clone.normal_pitch())?;
+        tts_clone.speak("This is normal pitch.", false)?;
+        tts_clone.set_pitch(original_pitch)?;
+    }
+    let Features { volume, .. } = tts_clone.supported_features();
+    if volume {
+        let original_volume = tts_clone.get_volume()?;
+        tts_clone.set_volume(tts_clone.max_volume())?;
+        tts_clone.speak("This is loud!", false)?;
+        tts_clone.set_volume(tts_clone.min_volume())?;
+        tts_clone.speak("This is quiet.", false)?;
+        tts_clone.set_volume(tts_clone.normal_volume())?;
+        tts_clone.speak("This is normal volume.", false)?;
+        tts_clone.set_volume(original_volume)?;
+    }
+    tts_clone.speak("Goodbye.", false)?;
+    let mut _input = String::new();
+    // The below is only needed to make the example run on MacOS because there is no NSRunLoop in this context.
+    // It shouldn't be needed in an app or game that almost certainly has one already.
+    #[cfg(target_os = "macos")]
+    {
+        let run_loop: id = unsafe { NSRunLoop::currentRunLoop() };
+        unsafe {
+            let _: () = msg_send![run_loop, run];
+        }
+    }
+    io::stdin().read_line(&mut _input)?;
+    Ok(())
+}

examples/hello_world.rs

@@ -71,6 +71,23 @@ fn main() -> Result<(), Error> {
         tts.speak("This is normal volume.", false)?;
         tts.set_volume(original_volume)?;
     }
+    let Features { voice, .. } = tts.supported_features();
+    if voice {
+        let voices = tts.voices()?;
+        println!("Available voices:\n===");
+        for v in &voices {
+            println!("{:?}", v);
+        }
+        let Features { get_voice, .. } = tts.supported_features();
+        let original_voice = if get_voice { tts.voice()? } else { None };
+        for v in &voices {
+            tts.set_voice(v)?;
+            tts.speak(format!("This is {}.", v.name()), false)?;
+        }
+        if let Some(original_voice) = original_voice {
+            tts.set_voice(&original_voice)?;
+        }
+    }
     tts.speak("Goodbye.", false)?;
     let mut _input = String::new();
     // The below is only needed to make the example run on MacOS because there is no NSRunLoop in this context.

examples/web/Cargo.toml

@@ -7,5 +7,8 @@ edition = "2018"
 # See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
 
 [dependencies]
-seed = "0.8"
+console_log = "0.2"
+log = "0.4"
+seed = "0.9"
 tts = { path = "../.." }
+wasm-bindgen = "= 0.2.80"

examples/web/index.html

@@ -1,5 +1,5 @@
 <!DOCTYPE html>
-<html>
+<html lang="en">
 
 <head>
     <title>Example</title>

examples/web/src/main.rs

@@ -15,13 +15,20 @@ enum Msg {
     RateChanged(String),
     PitchChanged(String),
     VolumeChanged(String),
+    VoiceChanged(String),
     Speak,
 }
 
 fn init(_: Url, _: &mut impl Orders<Msg>) -> Model {
-    let tts = Tts::default().unwrap();
+    let mut tts = Tts::default().unwrap();
+    if tts.voices().unwrap().iter().len() > 0 {
+        if tts.voice().unwrap().is_none() {
+            tts.set_voice(tts.voices().unwrap().first().unwrap())
+                .expect("Failed to set voice");
+        }
+    }
     Model {
-        text: Default::default(),
+        text: "Hello, world. This is a test of the current text-to-speech values.".into(),
         tts,
     }
 }
@@ -42,6 +49,13 @@ fn update(msg: Msg, model: &mut Model, _: &mut impl Orders<Msg>) {
             let volume = volume.parse::<f32>().unwrap();
             model.tts.set_volume(volume).unwrap();
         }
+        VoiceChanged(voice) => {
+            for v in model.tts.voices().unwrap() {
+                if v.id() == voice {
+                    model.tts.set_voice(&v).unwrap();
+                }
+            }
+        }
         Speak => {
             model.tts.speak(&model.text, false).unwrap();
         }
@@ -49,6 +63,7 @@ fn update(msg: Msg, model: &mut Model, _: &mut impl Orders<Msg>) {
 }
 
 fn view(model: &Model) -> Node<Msg> {
+    let should_show_voices = model.tts.voices().unwrap().iter().len() > 0;
     form![
         div![label![
             "Text to speak",
@@ -96,6 +111,36 @@ fn view(model: &Model) -> Node<Msg> {
                 input_ev(Ev::Input, Msg::VolumeChanged)
             ],
         ],],
+        if should_show_voices {
+            div![
+                label!["Voice"],
+                select![
+                    model.tts.voices().unwrap().iter().map(|v| {
+                        let selected = if let Some(voice) = model.tts.voice().unwrap() {
+                            voice.id() == v.id()
+                        } else {
+                            false
+                        };
+                        option![
+                            attrs! {
+                                At::Value => v.id()
+                            },
+                            if selected {
+                                attrs! {
+                                    At::Selected => selected
+                                }
+                            } else {
+                                attrs! {}
+                            },
+                            v.name()
+                        ]
+                    }),
+                    input_ev(Ev::Change, Msg::VoiceChanged)
+                ]
+            ]
+        } else {
+            div!["Your browser does not seem to support selecting voices."]
+        },
         button![
             "Speak",
             ev(Ev::Click, |e| {
@@ -107,5 +152,6 @@ fn view(model: &Model) -> Node<Msg> {
 }
 
 fn main() {
+    console_log::init().expect("Error initializing logger");
     App::start("app", init, update, view);
 }

src/backends/android.rs

@@ -1,18 +1,22 @@
 #[cfg(target_os = "android")]
-use std::collections::HashSet;
+use std::{
-use std::ffi::{CStr, CString};
+    collections::HashSet,
-use std::os::raw::c_void;
+    ffi::{CStr, CString},
-use std::sync::{Mutex, RwLock};
+    os::raw::c_void,
-use std::thread;
+    sync::{Mutex, RwLock},
-use std::time::Duration;
+    thread,
+    time::{Duration, Instant},
+};
 
-use jni::objects::{GlobalRef, JObject, JString};
+use jni::{
-use jni::sys::{jfloat, jint, JNI_VERSION_1_6};
+    objects::{GlobalRef, JObject, JString},
-use jni::{JNIEnv, JavaVM};
+    sys::{jfloat, jint, JNI_VERSION_1_6},
+    JNIEnv, JavaVM,
+};
 use lazy_static::lazy_static;
 use log::{error, info};
 
-use crate::{Backend, BackendId, Error, Features, UtteranceId, CALLBACKS};
+use crate::{Backend, BackendId, Error, Features, UtteranceId, Voice, CALLBACKS};
 
 lazy_static! {
     static ref BRIDGE: Mutex<Option<GlobalRef>> = Mutex::new(None);
@@ -198,12 +202,18 @@ impl Android {
             }
             let tts = env.new_global_ref(tts)?;
             // This hack makes my brain bleed.
+            const MAX_WAIT_TIME: Duration = Duration::from_millis(500);
+            let start = Instant::now();
+            // Wait a max of 500ms for initialization, then return an error to avoid hanging.
             loop {
                 {
                     let pending = PENDING_INITIALIZATIONS.read().unwrap();
                     if !(*pending).contains(&bid) {
                         break;
                     }
+                    if start.elapsed() > MAX_WAIT_TIME {
+                        return Err(Error::OperationFailed);
+                    }
                 }
                 thread::sleep(Duration::from_millis(5));
             }
@@ -238,6 +248,8 @@ impl Backend for Android {
             volume: false,
             is_speaking: true,
             utterance_callbacks: true,
+            voice: false,
+            get_voice: false,
         }
     }
 
@@ -375,4 +387,16 @@ impl Backend for Android {
         let rv = rv.z()?;
         Ok(rv)
     }
+
+    fn voice(&self) -> Result<Option<Voice>, Error> {
+        unimplemented!()
+    }
+
+    fn voices(&self) -> Result<Vec<Voice>, Error> {
+        unimplemented!()
+    }
+
+    fn set_voice(&mut self, _voice: &Voice) -> Result<(), Error> {
+        unimplemented!()
+    }
 }

src/backends/appkit.rs

@@ -1,5 +1,4 @@
 #[cfg(target_os = "macos")]
-#[link(name = "AppKit", kind = "framework")]
 use cocoa_foundation::base::{id, nil};
 use cocoa_foundation::foundation::NSString;
 use log::{info, trace};
@@ -7,18 +6,18 @@ use objc::declare::ClassDecl;
 use objc::runtime::*;
 use objc::*;
 
-use crate::{Backend, BackendId, Error, Features, UtteranceId};
+use crate::{Backend, BackendId, Error, Features, UtteranceId, Voice};
 
 #[derive(Clone, Debug)]
 pub(crate) struct AppKit(*mut Object, *mut Object);
 
 impl AppKit {
-    pub(crate) fn new() -> Self {
+    pub(crate) fn new() -> Result<Self, Error> {
         info!("Initializing AppKit backend");
         unsafe {
             let obj: *mut Object = msg_send![class!(NSSpeechSynthesizer), new];
-            let mut decl =
+            let mut decl = ClassDecl::new("MyNSSpeechSynthesizerDelegate", class!(NSObject))
-                ClassDecl::new("MyNSSpeechSynthesizerDelegate", class!(NSObject)).unwrap();
+                .ok_or(Error::OperationFailed)?;
             decl.add_ivar::<id>("synth");
             decl.add_ivar::<id>("strings");
 
@@ -82,11 +81,17 @@ impl AppKit {
 
             let delegate_class = decl.register();
             let delegate_obj: *mut Object = msg_send![delegate_class, new];
-            delegate_obj.as_mut().unwrap().set_ivar("synth", obj);
+            delegate_obj
+                .as_mut()
+                .ok_or(Error::OperationFailed)?
+                .set_ivar("synth", obj);
             let strings: id = msg_send![class!(NSMutableArray), new];
-            delegate_obj.as_mut().unwrap().set_ivar("strings", strings);
+            delegate_obj
+                .as_mut()
+                .ok_or(Error::OperationFailed)?
+                .set_ivar("strings", strings);
             let _: Object = msg_send![obj, setDelegate: delegate_obj];
-            AppKit(obj, delegate_obj)
+            Ok(AppKit(obj, delegate_obj))
         }
     }
 }
@@ -200,6 +205,18 @@ impl Backend for AppKit {
         let is_speaking: i8 = unsafe { msg_send![self.0, isSpeaking] };
         Ok(is_speaking != NO as i8)
     }
+
+    fn voice(&self) -> Result<Option<Voice>, Error> {
+        unimplemented!()
+    }
+
+    fn voices(&self) -> Result<Vec<Voice>, Error> {
+        unimplemented!()
+    }
+
+    fn set_voice(&mut self, _voice: &Voice) -> Result<(), Error> {
+        unimplemented!()
+    }
 }
 
 impl Drop for AppKit {

src/backends/av_foundation.rs

@@ -1,15 +1,17 @@
 #[cfg(any(target_os = "macos", target_os = "ios"))]
-#[link(name = "AVFoundation", kind = "framework")]
+use std::{str::FromStr, sync::Mutex};
-use std::sync::Mutex;
 
 use cocoa_foundation::base::{id, nil, NO};
 use cocoa_foundation::foundation::NSString;
+use core_foundation::array::CFArray;
+use core_foundation::string::CFString;
 use lazy_static::lazy_static;
 use log::{info, trace};
 use objc::runtime::{Object, Sel};
 use objc::{class, declare::ClassDecl, msg_send, sel, sel_impl};
+use unic_langid::LanguageIdentifier;
 
-use crate::{Backend, BackendId, Error, Features, UtteranceId, CALLBACKS};
+use crate::{Backend, BackendId, Error, Features, Gender, UtteranceId, Voice, CALLBACKS};
 
 #[derive(Clone, Debug)]
 pub(crate) struct AvFoundation {
@@ -19,6 +21,7 @@ pub(crate) struct AvFoundation {
     rate: f32,
     volume: f32,
     pitch: f32,
+    voice: Option<Voice>,
 }
 
 lazy_static! {
@@ -26,9 +29,10 @@ lazy_static! {
 }
 
 impl AvFoundation {
-    pub(crate) fn new() -> Self {
+    pub(crate) fn new() -> Result<Self, Error> {
         info!("Initializing AVFoundation backend");
-        let mut decl = ClassDecl::new("MyNSSpeechSynthesizerDelegate", class!(NSObject)).unwrap();
+        let mut decl = ClassDecl::new("MyNSSpeechSynthesizerDelegate", class!(NSObject))
+            .ok_or(Error::OperationFailed)?;
         decl.add_ivar::<u64>("backend_id");
 
         extern "C" fn speech_synthesizer_did_start_speech_utterance(
@@ -142,10 +146,11 @@ impl AvFoundation {
                 rate: 0.5,
                 volume: 1.,
                 pitch: 1.,
+                voice: None,
             }
         };
         *backend_id += 1;
-        rv
+        Ok(rv)
     }
 }
 
@@ -161,6 +166,8 @@ impl Backend for AvFoundation {
             pitch: true,
             volume: true,
             is_speaking: true,
+            voice: true,
+            get_voice: false,
             utterance_callbacks: true,
         }
     }
@@ -185,6 +192,12 @@ impl Backend for AvFoundation {
             let _: () = msg_send![utterance, setVolume: self.volume];
             trace!("Setting pitch to {}", self.pitch);
             let _: () = msg_send![utterance, setPitchMultiplier: self.pitch];
+            if let Some(voice) = &self.voice {
+                let mut vid = NSString::alloc(nil);
+                vid = vid.init_str(&voice.id());
+                let v: id = msg_send![class!(AVSpeechSynthesisVoice), voiceWithIdentifier: vid];
+                let _: () = msg_send![utterance, setVoice: v];
+            }
             trace!("Enqueuing");
             let _: () = msg_send![self.synth, speakUtterance: utterance];
             trace!("Done queuing");
@@ -271,6 +284,42 @@ impl Backend for AvFoundation {
         let is_speaking: i8 = unsafe { msg_send![self.synth, isSpeaking] };
         Ok(is_speaking != NO as i8)
     }
+
+    fn voice(&self) -> Result<Option<Voice>, Error> {
+        unimplemented!()
+    }
+
+    fn voices(&self) -> Result<Vec<Voice>, Error> {
+        let voices: CFArray = unsafe { msg_send![class!(AVSpeechSynthesisVoice), speechVoices] };
+        let rv = voices
+            .iter()
+            .map(|v| {
+                let id: CFString = unsafe { msg_send![*v as *const Object, identifier] };
+                let name: CFString = unsafe { msg_send![*v as *const Object, name] };
+                let gender: i64 = unsafe { msg_send![*v as *const Object, gender] };
+                let gender = match gender {
+                    1 => Some(Gender::Male),
+                    2 => Some(Gender::Female),
+                    _ => None,
+                };
+                let language: CFString = unsafe { msg_send![*v as *const Object, language] };
+                let language = language.to_string();
+                let language = LanguageIdentifier::from_str(&language).unwrap();
+                Voice {
+                    id: id.to_string(),
+                    name: name.to_string(),
+                    gender,
+                    language,
+                }
+            })
+            .collect();
+        Ok(rv)
+    }
+
+    fn set_voice(&mut self, voice: &Voice) -> Result<(), Error> {
+        self.voice = Some(voice.clone());
+        Ok(())
+    }
 }
 
 impl Drop for AvFoundation {

src/backends/speech_dispatcher.rs

@@ -1,12 +1,12 @@
 #[cfg(target_os = "linux")]
-use std::collections::HashMap;
+use std::{collections::HashMap, str::FromStr, sync::Mutex};
-use std::sync::Mutex;
 
 use lazy_static::*;
 use log::{info, trace};
 use speech_dispatcher::*;
+use unic_langid::LanguageIdentifier;
 
-use crate::{Backend, BackendId, Error, Features, UtteranceId, CALLBACKS};
+use crate::{Backend, BackendId, Error, Features, UtteranceId, Voice, CALLBACKS};
 
 #[derive(Clone, Debug)]
 pub(crate) struct SpeechDispatcher(Connection);
@@ -19,9 +19,9 @@ lazy_static! {
 }
 
 impl SpeechDispatcher {
-    pub(crate) fn new() -> Self {
+    pub(crate) fn new() -> std::result::Result<Self, Error> {
         info!("Initializing SpeechDispatcher backend");
-        let connection = speech_dispatcher::Connection::open("tts", "tts", "tts", Mode::Threaded);
+        let connection = speech_dispatcher::Connection::open("tts", "tts", "tts", Mode::Threaded)?;
         let sd = SpeechDispatcher(connection);
         let mut speaking = SPEAKING.lock().unwrap();
         speaking.insert(sd.0.client_id(), false);
@@ -66,7 +66,7 @@ impl SpeechDispatcher {
             let mut speaking = SPEAKING.lock().unwrap();
             speaking.insert(client_id, true);
         })));
-        sd
+        Ok(sd)
     }
 }
 
@@ -82,6 +82,8 @@ impl Backend for SpeechDispatcher {
             pitch: true,
             volume: true,
             is_speaking: true,
+            voice: true,
+            get_voice: false,
             utterance_callbacks: true,
         }
     }
@@ -93,11 +95,11 @@ impl Backend for SpeechDispatcher {
         }
         let single_char = text.to_string().capacity() == 1;
         if single_char {
-            self.0.set_punctuation(Punctuation::All);
+            self.0.set_punctuation(Punctuation::All)?;
         }
         let id = self.0.say(Priority::Important, text);
         if single_char {
-            self.0.set_punctuation(Punctuation::None);
+            self.0.set_punctuation(Punctuation::None)?;
         }
         if let Some(id) = id {
             Ok(Some(UtteranceId::SpeechDispatcher(id)))
@@ -108,7 +110,7 @@ impl Backend for SpeechDispatcher {
 
     fn stop(&mut self) -> Result<(), Error> {
         trace!("stop()");
-        self.0.cancel();
+        self.0.cancel()?;
         Ok(())
     }
 
@@ -129,7 +131,7 @@ impl Backend for SpeechDispatcher {
     }
 
     fn set_rate(&mut self, rate: f32) -> Result<(), Error> {
-        self.0.set_voice_rate(rate as i32);
+        self.0.set_voice_rate(rate as i32)?;
         Ok(())
     }
 
@@ -150,7 +152,7 @@ impl Backend for SpeechDispatcher {
     }
 
     fn set_pitch(&mut self, pitch: f32) -> Result<(), Error> {
-        self.0.set_voice_pitch(pitch as i32);
+        self.0.set_voice_pitch(pitch as i32)?;
         Ok(())
     }
 
@@ -171,7 +173,7 @@ impl Backend for SpeechDispatcher {
     }
 
     fn set_volume(&mut self, volume: f32) -> Result<(), Error> {
-        self.0.set_volume(volume as i32);
+        self.0.set_volume(volume as i32)?;
         Ok(())
     }
 
@@ -180,6 +182,35 @@ impl Backend for SpeechDispatcher {
         let is_speaking = speaking.get(&self.0.client_id()).unwrap();
         Ok(*is_speaking)
     }
+
+    fn voices(&self) -> Result<Vec<Voice>, Error> {
+        let rv = self
+            .0
+            .list_synthesis_voices()?
+            .iter()
+            .map(|v| Voice {
+                id: v.name.clone(),
+                name: v.name.clone(),
+                gender: None,
+                language: LanguageIdentifier::from_str(&v.language).unwrap(),
+            })
+            .collect::<Vec<Voice>>();
+        Ok(rv)
+    }
+
+    fn voice(&self) -> Result<Option<Voice>, Error> {
+        unimplemented!()
+    }
+
+    fn set_voice(&mut self, voice: &Voice) -> Result<(), Error> {
+        for v in self.0.list_synthesis_voices()? {
+            if v.name == voice.name {
+                self.0.set_synthesis_voice(&v)?;
+                return Ok(());
+            }
+        }
+        Err(Error::OperationFailed)
+    }
 }
 
 impl Drop for SpeechDispatcher {

src/backends/tolk.rs

@@ -4,7 +4,7 @@ use std::sync::Arc;
 use log::{info, trace};
 use tolk::Tolk as TolkPtr;
 
-use crate::{Backend, BackendId, Error, Features, UtteranceId};
+use crate::{Backend, BackendId, Error, Features, UtteranceId, Voice};
 
 #[derive(Clone, Debug)]
 pub(crate) struct Tolk(Arc<TolkPtr>);
@@ -108,4 +108,16 @@ impl Backend for Tolk {
     fn is_speaking(&self) -> Result<bool, Error> {
         unimplemented!()
     }
+
+    fn voice(&self) -> Result<Option<Voice>, Error> {
+        unimplemented!()
+    }
+
+    fn voices(&self) -> Result<Vec<Voice>, Error> {
+        unimplemented!()
+    }
+
+    fn set_voice(&mut self, _voice: &Voice) -> Result<(), Error> {
+        unimplemented!()
+    }
 }

src/backends/web.rs

@@ -1,16 +1,17 @@
 #[cfg(target_arch = "wasm32")]
-use std::sync::Mutex;
+use std::{str::FromStr, sync::Mutex};
 
 use lazy_static::lazy_static;
 use log::{info, trace};
+use unic_langid::LanguageIdentifier;
 use wasm_bindgen::prelude::*;
 use wasm_bindgen::JsCast;
 use web_sys::{
     SpeechSynthesisErrorCode, SpeechSynthesisErrorEvent, SpeechSynthesisEvent,
-    SpeechSynthesisUtterance,
+    SpeechSynthesisUtterance, SpeechSynthesisVoice,
 };
 
-use crate::{Backend, BackendId, Error, Features, UtteranceId, CALLBACKS};
+use crate::{Backend, BackendId, Error, Features, UtteranceId, Voice, CALLBACKS};
 
 #[derive(Clone, Debug)]
 pub struct Web {
@@ -18,6 +19,7 @@ pub struct Web {
     rate: f32,
     pitch: f32,
     volume: f32,
+    voice: Option<SpeechSynthesisVoice>,
 }
 
 lazy_static! {
@@ -35,6 +37,7 @@ impl Web {
             rate: 1.,
             pitch: 1.,
             volume: 1.,
+            voice: None,
         };
         *backend_id += 1;
         Ok(rv)
@@ -53,6 +56,8 @@ impl Backend for Web {
             pitch: true,
             volume: true,
             is_speaking: true,
+            voice: true,
+            get_voice: true,
             utterance_callbacks: true,
         }
     }
@@ -63,6 +68,9 @@ impl Backend for Web {
         utterance.set_rate(self.rate);
         utterance.set_pitch(self.pitch);
         utterance.set_volume(self.volume);
+        if self.voice.is_some() {
+            utterance.set_voice(self.voice.as_ref());
+        }
         let id = self.id().unwrap();
         let mut uid = NEXT_UTTERANCE_ID.lock().unwrap();
         let utterance_id = UtteranceId::Web(*uid);
@@ -196,6 +204,55 @@ impl Backend for Web {
             Err(Error::NoneError)
         }
     }
+
+    fn voice(&self) -> Result<Option<Voice>, Error> {
+        if let Some(voice) = &self.voice {
+            Ok(Some(voice.clone().into()))
+        } else {
+            if let Some(window) = web_sys::window() {
+                let speech_synthesis = window.speech_synthesis().unwrap();
+                for voice in speech_synthesis.get_voices().iter() {
+                    let voice: SpeechSynthesisVoice = voice.into();
+                    if voice.default() {
+                        return Ok(Some(voice.into()));
+                    }
+                }
+            } else {
+                return Err(Error::NoneError);
+            }
+            Ok(None)
+        }
+    }
+
+    fn voices(&self) -> Result<Vec<Voice>, Error> {
+        if let Some(window) = web_sys::window() {
+            let speech_synthesis = window.speech_synthesis().unwrap();
+            let mut rv: Vec<Voice> = vec![];
+            for v in speech_synthesis.get_voices().iter() {
+                let v: SpeechSynthesisVoice = v.into();
+                rv.push(v.into());
+            }
+            Ok(rv)
+        } else {
+            Err(Error::NoneError)
+        }
+    }
+
+    fn set_voice(&mut self, voice: &Voice) -> Result<(), Error> {
+        if let Some(window) = web_sys::window() {
+            let speech_synthesis = window.speech_synthesis().unwrap();
+            for v in speech_synthesis.get_voices().iter() {
+                let v: SpeechSynthesisVoice = v.into();
+                if v.voice_uri() == voice.id {
+                    self.voice = Some(v);
+                    return Ok(());
+                }
+            }
+            return Err(Error::OperationFailed);
+        } else {
+            Err(Error::NoneError)
+        }
+    }
 }
 
 impl Drop for Web {
@@ -204,3 +261,15 @@ impl Drop for Web {
         mappings.retain(|v| v.0 != self.id);
     }
 }
+
+impl From<SpeechSynthesisVoice> for Voice {
+    fn from(other: SpeechSynthesisVoice) -> Self {
+        let language = LanguageIdentifier::from_str(&other.lang()).unwrap();
+        Voice {
+            id: other.voice_uri(),
+            name: other.name(),
+            gender: None,
+            language,
+        }
+    }
+}

src/backends/winrt.rs

@@ -1,30 +1,31 @@
 #[cfg(windows)]
-use std::collections::{HashMap, VecDeque};
+use std::{
-use std::sync::Mutex;
+    collections::{HashMap, VecDeque},
+    str::FromStr,
+    sync::Mutex,
+};
 
 use lazy_static::lazy_static;
 use log::{info, trace};
-
+use unic_langid::LanguageIdentifier;
-mod bindings;
+use windows::{
-
-use bindings::Windows::{
     Foundation::TypedEventHandler,
     Media::{
         Core::MediaSource,
         Playback::{MediaPlayer, MediaPlayerAudioCategory},
-        SpeechSynthesis::SpeechSynthesizer,
+        SpeechSynthesis::{SpeechSynthesizer, VoiceGender, VoiceInformation},
     },
 };
 
-use crate::{Backend, BackendId, Error, Features, UtteranceId, CALLBACKS};
+use crate::{Backend, BackendId, Error, Features, Gender, UtteranceId, Voice, CALLBACKS};
 
-impl From<windows::Error> for Error {
+impl From<windows::core::Error> for Error {
-    fn from(e: windows::Error) -> Self {
+    fn from(e: windows::core::Error) -> Self {
         Error::WinRt(e)
     }
 }
 
-#[derive(Clone, Debug)]
+#[derive(Clone)]
 pub struct WinRt {
     id: BackendId,
     synth: SpeechSynthesizer,
@@ -32,6 +33,7 @@ pub struct WinRt {
     rate: f32,
     pitch: f32,
     volume: f32,
+    voice: VoiceInformation,
 }
 
 struct Utterance {
@@ -40,6 +42,7 @@ struct Utterance {
     rate: f32,
     pitch: f32,
     volume: f32,
+    voice: VoiceInformation,
 }
 
 lazy_static! {
@@ -81,7 +84,7 @@ impl WinRt {
         backend_to_speech_synthesizer.insert(bid, synth.clone());
         drop(backend_to_speech_synthesizer);
         let bid_clone = bid;
-        player.MediaEnded(TypedEventHandler::new(
+        player.MediaEnded(&TypedEventHandler::new(
             move |sender: &Option<MediaPlayer>, _args| {
                 if let Some(sender) = sender {
                     let backend_to_media_player = BACKEND_TO_MEDIA_PLAYER.lock().unwrap();
@@ -105,13 +108,14 @@ impl WinRt {
                                         tts.Options()?.SetSpeakingRate(utterance.rate.into())?;
                                         tts.Options()?.SetAudioPitch(utterance.pitch.into())?;
                                         tts.Options()?.SetAudioVolume(utterance.volume.into())?;
-                                        let stream = tts
+                                        tts.SetVoice(&utterance.voice)?;
-                                            .SynthesizeTextToStreamAsync(utterance.text.as_str())?
+                                        let text = &utterance.text;
-                                            .get()?;
+                                        let stream =
+                                            tts.SynthesizeTextToStreamAsync(&text.into())?.get()?;
                                         let content_type = stream.ContentType()?;
                                         let source =
-                                            MediaSource::CreateFromStream(stream, content_type)?;
+                                            MediaSource::CreateFromStream(&stream, &content_type)?;
-                                        sender.SetSource(source)?;
+                                        sender.SetSource(&source)?;
                                         sender.Play()?;
                                         if let Some(callback) = callbacks.utterance_begin.as_mut() {
                                             callback(utterance.id);
@@ -132,6 +136,7 @@ impl WinRt {
             rate: 1.,
             pitch: 1.,
             volume: 1.,
+            voice: SpeechSynthesizer::DefaultVoice()?,
         })
     }
 }
@@ -148,6 +153,8 @@ impl Backend for WinRt {
             pitch: true,
             volume: true,
             is_speaking: true,
+            voice: true,
+            get_voice: true,
             utterance_callbacks: true,
         }
     }
@@ -177,6 +184,7 @@ impl Backend for WinRt {
                     rate: self.rate,
                     pitch: self.pitch,
                     volume: self.volume,
+                    voice: self.voice.clone(),
                 };
                 utterances.push_back(utterance);
             }
@@ -185,10 +193,14 @@ impl Backend for WinRt {
             self.synth.Options()?.SetSpeakingRate(self.rate.into())?;
             self.synth.Options()?.SetAudioPitch(self.pitch.into())?;
             self.synth.Options()?.SetAudioVolume(self.volume.into())?;
-            let stream = self.synth.SynthesizeTextToStreamAsync(text)?.get()?;
+            self.synth.SetVoice(&self.voice)?;
+            let stream = self
+                .synth
+                .SynthesizeTextToStreamAsync(&text.into())?
+                .get()?;
             let content_type = stream.ContentType()?;
-            let source = MediaSource::CreateFromStream(stream, content_type)?;
+            let source = MediaSource::CreateFromStream(&stream, &content_type)?;
-            self.player.SetSource(source)?;
+            self.player.SetSource(&source)?;
             self.player.Play()?;
             let mut callbacks = CALLBACKS.lock().unwrap();
             let callbacks = callbacks.get_mut(&self.id).unwrap();
@@ -292,6 +304,31 @@ impl Backend for WinRt {
         let utterances = utterances.get(&self.id).unwrap();
         Ok(!utterances.is_empty())
     }
+
+    fn voice(&self) -> Result<Option<Voice>, Error> {
+        let voice = self.synth.Voice()?;
+        let voice = voice.try_into()?;
+        Ok(Some(voice))
+    }
+
+    fn voices(&self) -> Result<Vec<Voice>, Error> {
+        let mut rv: Vec<Voice> = vec![];
+        for voice in SpeechSynthesizer::AllVoices()? {
+            rv.push(voice.try_into()?);
+        }
+        Ok(rv)
+    }
+
+    fn set_voice(&mut self, voice: &Voice) -> Result<(), Error> {
+        for v in SpeechSynthesizer::AllVoices()? {
+            let vid: String = v.Id()?.try_into()?;
+            if vid == voice.id {
+                self.voice = v;
+                return Ok(());
+            }
+        }
+        Err(Error::OperationFailed)
+    }
 }
 
 impl Drop for WinRt {
@@ -305,3 +342,24 @@ impl Drop for WinRt {
         utterances.remove(&id);
     }
 }
+
+impl TryInto<Voice> for VoiceInformation {
+    type Error = Error;
+
+    fn try_into(self) -> Result<Voice, Self::Error> {
+        let gender = self.Gender()?;
+        let gender = if gender == VoiceGender::Male {
+            Gender::Male
+        } else {
+            Gender::Female
+        };
+        let language: String = self.Language()?.try_into()?;
+        let language = LanguageIdentifier::from_str(&language).unwrap();
+        Ok(Voice {
+            id: self.Id()?.try_into()?,
+            name: self.DisplayName()?.try_into()?,
+            gender: Some(gender),
+            language,
+        })
+    }
+}

src/backends/winrt/bindings.rs

@@ -1 +0,0 @@
-::windows::include_bindings!();

src/lib.rs

@@ -1,22 +1,23 @@
-/*!
+//! * a Text-To-Speech (TTS) library providing high-level interfaces to a variety of backends.
- * a Text-To-Speech (TTS) library providing high-level interfaces to a variety of backends.
+//!  * Currently supported backends are:
- * Currently supported backends are:
+//!  * * Windows
- * * Windows
+//!  *   * Screen readers/SAPI via Tolk (requires `tolk` Cargo feature)
- *   * Screen readers/SAPI via Tolk (requires `tolk` Cargo feature)
+//!  *   * WinRT
- *   * WinRT
+//!  * * Linux via [Speech Dispatcher](https://freebsoft.org/speechd)
- * * Linux via [Speech Dispatcher](https://freebsoft.org/speechd)
+//!  * * MacOS/iOS
- * * MacOS/iOS
+//!  *   * AppKit on MacOS 10.13 and below
- *   * AppKit on MacOS 10.13 and below
+//!  *   * AVFoundation on MacOS 10.14 and above, and iOS
- *   * AVFoundation on MacOS 10.14 and above, and iOS
+//!  * * Android
- * * Android
+//!  * * WebAssembly
- * * WebAssembly
- */
 
-use std::boxed::Box;
 use std::collections::HashMap;
 #[cfg(target_os = "macos")]
 use std::ffi::CStr;
-use std::sync::Mutex;
+use std::fmt;
+#[cfg(windows)]
+use std::string::FromUtf16Error;
+use std::sync::{Arc, Mutex};
+use std::{boxed::Box, sync::RwLock};
 
 #[cfg(any(target_os = "macos", target_os = "ios"))]
 use cocoa_foundation::base::id;
@@ -26,59 +27,134 @@ use lazy_static::lazy_static;
 use libc::c_char;
 #[cfg(target_os = "macos")]
 use objc::{class, msg_send, sel, sel_impl};
+#[cfg(target_os = "linux")]
+use speech_dispatcher::Error as SpeechDispatcherError;
 use thiserror::Error;
 #[cfg(all(windows, feature = "tolk"))]
 use tolk::Tolk;
+pub use unic_langid::LanguageIdentifier;
 
 mod backends;
 #[cfg(feature = "ffi")]
 pub mod ffi;
 
 #[repr(C)]
-#[derive(Clone, Copy, Debug)]
+#[derive(Clone, Copy, Debug, Eq, Hash, PartialEq, PartialOrd, Ord)]
+#[cfg_attr(feature = "serde", derive(serde::Serialize, serde::Deserialize))]
 pub enum Backends {
-    #[cfg(target_os = "linux")]
+    #[cfg(target_os = "android")]
-    SpeechDispatcher,
+    Android,
-    #[cfg(target_arch = "wasm32")]
-    Web,
-    #[cfg(all(windows, feature = "tolk"))]
-    Tolk,
-    #[cfg(windows)]
-    WinRt,
     #[cfg(target_os = "macos")]
     AppKit,
     #[cfg(any(target_os = "macos", target_os = "ios"))]
     AvFoundation,
-    #[cfg(target_os = "android")]
+    #[cfg(target_os = "linux")]
-    Android,
+    SpeechDispatcher,
+    #[cfg(all(windows, feature = "tolk"))]
+    Tolk,
+    #[cfg(target_arch = "wasm32")]
+    Web,
+    #[cfg(windows)]
+    WinRt,
 }
 
-#[derive(Clone, Copy, Debug, Eq, Hash, PartialEq)]
+impl fmt::Display for Backends {
-pub enum BackendId {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> Result<(), fmt::Error> {
+        match self {
+            #[cfg(target_os = "android")]
+            Backends::Android => writeln!(f, "Android"),
+            #[cfg(target_os = "macos")]
+            Backends::AppKit => writeln!(f, "AppKit"),
+            #[cfg(any(target_os = "macos", target_os = "ios"))]
+            Backends::AvFoundation => writeln!(f, "AVFoundation"),
             #[cfg(target_os = "linux")]
-    SpeechDispatcher(u64),
+            Backends::SpeechDispatcher => writeln!(f, "Speech Dispatcher"),
+            #[cfg(all(windows, feature = "tolk"))]
+            Backends::Tolk => writeln!(f, "Tolk"),
             #[cfg(target_arch = "wasm32")]
-    Web(u64),
+            Backends::Web => writeln!(f, "Web"),
             #[cfg(windows)]
-    WinRt(u64),
+            Backends::WinRt => writeln!(f, "Windows Runtime"),
+        }
+    }
+}
+
+#[derive(Clone, Copy, Debug, Eq, Hash, PartialEq, PartialOrd, Ord)]
+#[cfg_attr(feature = "serde", derive(serde::Serialize, serde::Deserialize))]
+pub enum BackendId {
+    #[cfg(target_os = "android")]
+    Android(u64),
     #[cfg(any(target_os = "macos", target_os = "ios"))]
     AvFoundation(u64),
-    #[cfg(target_os = "android")]
-    Android(u64),
-}
-
-#[derive(Clone, Copy, Debug, Eq, Hash, PartialEq)]
-pub enum UtteranceId {
     #[cfg(target_os = "linux")]
     SpeechDispatcher(u64),
     #[cfg(target_arch = "wasm32")]
     Web(u64),
     #[cfg(windows)]
     WinRt(u64),
+}
+
+impl fmt::Display for BackendId {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> Result<(), fmt::Error> {
+        match self {
+            #[cfg(target_os = "android")]
+            BackendId::Android(id) => writeln!(f, "{}", id),
             #[cfg(any(target_os = "macos", target_os = "ios"))]
-    AvFoundation(id),
+            BackendId::AvFoundation(id) => writeln!(f, "{}", id),
+            #[cfg(target_os = "linux")]
+            BackendId::SpeechDispatcher(id) => writeln!(f, "{}", id),
+            #[cfg(target_arch = "wasm32")]
+            BackendId::Web(id) => writeln!(f, "Web({})", id),
+            #[cfg(windows)]
+            BackendId::WinRt(id) => writeln!(f, "{}", id),
+        }
+    }
+}
+
+// # Note
+//
+// Most trait implementations are blocked by cocoa_foundation::base::id;
+// which is a type alias for objc::runtime::Object, which only implements Debug.
+#[derive(Debug)]
+#[cfg_attr(
+    not(any(target_os = "macos", target_os = "ios")),
+    derive(Clone, Copy, Eq, Hash, PartialEq, PartialOrd, Ord)
+)]
+#[cfg_attr(
+    all(feature = "serde", not(any(target_os = "macos", target_os = "ios"))),
+    derive(serde::Serialize, serde::Deserialize)
+)]
+pub enum UtteranceId {
     #[cfg(target_os = "android")]
     Android(u64),
+    #[cfg(any(target_os = "macos", target_os = "ios"))]
+    AvFoundation(id),
+    #[cfg(target_os = "linux")]
+    SpeechDispatcher(u64),
+    #[cfg(target_arch = "wasm32")]
+    Web(u64),
+    #[cfg(windows)]
+    WinRt(u64),
+}
+
+// # Note
+//
+// Display is not implemented by cocoa_foundation::base::id;
+// which is a type alias for objc::runtime::Object, which only implements Debug.
+#[cfg(not(any(target_os = "macos", target_os = "ios")))]
+impl fmt::Display for UtteranceId {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> Result<(), fmt::Error> {
+        match self {
+            #[cfg(target_os = "android")]
+            UtteranceId::Android(id) => writeln!(f, "{}", id),
+            #[cfg(target_os = "linux")]
+            UtteranceId::SpeechDispatcher(id) => writeln!(f, "{}", id),
+            #[cfg(target_arch = "wasm32")]
+            UtteranceId::Web(id) => writeln!(f, "Web({})", id),
+            #[cfg(windows)]
+            UtteranceId::WinRt(id) => writeln!(f, "{}", id),
+        }
+    }
 }
 
 unsafe impl Send for UtteranceId {}
@@ -86,26 +162,29 @@ unsafe impl Send for UtteranceId {}
 unsafe impl Sync for UtteranceId {}
 
 #[repr(C)]
+#[derive(Clone, Copy, Debug, Default, Eq, Hash, PartialEq, PartialOrd, Ord)]
+#[cfg_attr(feature = "serde", derive(serde::Serialize, serde::Deserialize))]
 pub struct Features {
-    pub stop: bool,
-    pub rate: bool,
-    pub pitch: bool,
-    pub volume: bool,
     pub is_speaking: bool,
+    pub pitch: bool,
+    pub rate: bool,
+    pub stop: bool,
     pub utterance_callbacks: bool,
+    pub voice: bool,
+    pub get_voice: bool,
+    pub volume: bool,
 }
 
-impl Default for Features {
+impl fmt::Display for Features {
-    fn default() -> Self {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> Result<(), fmt::Error> {
-        Self {
+        writeln!(f, "{:#?}", self)
-            stop: false,
-            rate: false,
-            pitch: false,
-            volume: false,
-            is_speaking: false,
-            utterance_callbacks: false,
     }
 }
+
+impl Features {
+    pub fn new() -> Self {
+        Self::default()
+    }
 }
 
 #[derive(Debug, Error)]
@@ -117,11 +196,17 @@ pub enum Error {
     #[error("Operation failed")]
     OperationFailed,
     #[cfg(target_arch = "wasm32")]
-    #[error("JavaScript error: [0])]")]
+    #[error("JavaScript error: [0]")]
     JavaScriptError(wasm_bindgen::JsValue),
+    #[cfg(target_os = "linux")]
+    #[error("Speech Dispatcher error: {0}")]
+    SpeechDispatcher(#[from] SpeechDispatcherError),
     #[cfg(windows)]
     #[error("WinRT error")]
-    WinRt(windows::Error),
+    WinRt(windows::core::Error),
+    #[cfg(windows)]
+    #[error("UTF string conversion failed")]
+    UtfStringConversionFailed(#[from] FromUtf16Error),
     #[error("Unsupported feature")]
     UnsupportedFeature,
     #[error("Out of range")]
@@ -132,7 +217,7 @@ pub enum Error {
 }
 
 #[clonable]
-trait Backend: Clone {
+pub trait Backend: Clone {
     fn id(&self) -> Option<BackendId>;
     fn supported_features(&self) -> Features;
     fn speak(&mut self, text: &str, interrupt: bool) -> Result<Option<UtteranceId>, Error>;
@@ -153,6 +238,9 @@ trait Backend: Clone {
     fn get_volume(&self) -> Result<f32, Error>;
     fn set_volume(&mut self, volume: f32) -> Result<(), Error>;
     fn is_speaking(&self) -> Result<bool, Error>;
+    fn voices(&self) -> Result<Vec<Voice>, Error>;
+    fn voice(&self) -> Result<Option<Voice>, Error>;
+    fn set_voice(&mut self, voice: &Voice) -> Result<(), Error>;
 }
 
 #[derive(Default)]
@@ -174,30 +262,31 @@ lazy_static! {
 }
 
 #[derive(Clone)]
-pub struct Tts(Box<dyn Backend>);
+pub struct Tts(Arc<RwLock<Box<dyn Backend>>>);
 
 unsafe impl Send for Tts {}
 
 unsafe impl Sync for Tts {}
 
 impl Tts {
-    /**
+    /// Create a new `TTS` instance with the specified backend.
-     * Create a new `TTS` instance with the specified backend.
-     */
     pub fn new(backend: Backends) -> Result<Tts, Error> {
         let backend = match backend {
             #[cfg(target_os = "linux")]
-            Backends::SpeechDispatcher => Ok(Tts(Box::new(backends::SpeechDispatcher::new()))),
+            Backends::SpeechDispatcher => {
+                let tts = backends::SpeechDispatcher::new()?;
+                Ok(Tts(Arc::new(RwLock::new(Box::new(tts)))))
+            }
             #[cfg(target_arch = "wasm32")]
             Backends::Web => {
                 let tts = backends::Web::new()?;
-                Ok(Tts(Box::new(tts)))
+                Ok(Tts(Arc::new(RwLock::new(Box::new(tts)))))
             }
             #[cfg(all(windows, feature = "tolk"))]
             Backends::Tolk => {
                 let tts = backends::Tolk::new();
                 if let Some(tts) = tts {
-                    Ok(Tts(Box::new(tts)))
+                    Ok(Tts(Arc::new(RwLock::new(Box::new(tts)))))
                 } else {
                     Err(Error::NoneError)
                 }
@@ -205,20 +294,24 @@ impl Tts {
             #[cfg(windows)]
             Backends::WinRt => {
                 let tts = backends::WinRt::new()?;
-                Ok(Tts(Box::new(tts)))
+                Ok(Tts(Arc::new(RwLock::new(Box::new(tts)))))
             }
             #[cfg(target_os = "macos")]
-            Backends::AppKit => Ok(Tts(Box::new(backends::AppKit::new()))),
+            Backends::AppKit => Ok(Tts(Arc::new(RwLock::new(Box::new(
+                backends::AppKit::new()?
+            ))))),
             #[cfg(any(target_os = "macos", target_os = "ios"))]
-            Backends::AvFoundation => Ok(Tts(Box::new(backends::AvFoundation::new()))),
+            Backends::AvFoundation => Ok(Tts(Arc::new(RwLock::new(Box::new(
+                backends::AvFoundation::new()?,
+            ))))),
             #[cfg(target_os = "android")]
             Backends::Android => {
                 let tts = backends::Android::new()?;
-                Ok(Tts(Box::new(tts)))
+                Ok(Tts(Arc::new(RwLock::new(Box::new(tts)))))
             }
         };
         if let Ok(backend) = backend {
-            if let Some(id) = backend.0.id() {
+            if let Some(id) = backend.0.read().unwrap().id() {
                 let mut callbacks = CALLBACKS.lock().unwrap();
                 callbacks.insert(id, Callbacks::default());
             }
@@ -267,82 +360,70 @@ impl Tts {
         tts
     }
 
-    /**
+    /// Returns the features supported by this TTS engine
-     * Returns the features supported by this TTS engine
-     */
     pub fn supported_features(&self) -> Features {
-        self.0.supported_features()
+        self.0.read().unwrap().supported_features()
     }
 
-    /**
+    /// Speaks the specified text, optionally interrupting current speech.
-     * Speaks the specified text, optionally interrupting current speech.
-     */
     pub fn speak<S: Into<String>>(
         &mut self,
         text: S,
         interrupt: bool,
     ) -> Result<Option<UtteranceId>, Error> {
-        self.0.speak(text.into().as_str(), interrupt)
+        self.0
+            .write()
+            .unwrap()
+            .speak(text.into().as_str(), interrupt)
     }
 
-    /**
+    /// Stops current speech.
-     * Stops current speech.
-     */
     pub fn stop(&mut self) -> Result<&Self, Error> {
         let Features { stop, .. } = self.supported_features();
         if stop {
-            self.0.stop()?;
+            self.0.write().unwrap().stop()?;
             Ok(self)
         } else {
             Err(Error::UnsupportedFeature)
         }
     }
 
-    /**
+    /// Returns the minimum rate for this speech synthesizer.
-     * Returns the minimum rate for this speech synthesizer.
-     */
     pub fn min_rate(&self) -> f32 {
-        self.0.min_rate()
+        self.0.read().unwrap().min_rate()
     }
 
-    /**
+    /// Returns the maximum rate for this speech synthesizer.
-     * Returns the maximum rate for this speech synthesizer.
-     */
     pub fn max_rate(&self) -> f32 {
-        self.0.max_rate()
+        self.0.read().unwrap().max_rate()
     }
 
-    /**
+    /// Returns the normal rate for this speech synthesizer.
-     * Returns the normal rate for this speech synthesizer.
-     */
     pub fn normal_rate(&self) -> f32 {
-        self.0.normal_rate()
+        self.0.read().unwrap().normal_rate()
     }
 
-    /**
+    /// Gets the current speech rate.
-     * Gets the current speech rate.
-     */
     pub fn get_rate(&self) -> Result<f32, Error> {
         let Features { rate, .. } = self.supported_features();
         if rate {
-            self.0.get_rate()
+            self.0.read().unwrap().get_rate()
         } else {
             Err(Error::UnsupportedFeature)
         }
     }
 
-    /**
+    /// Sets the desired speech rate.
-     * Sets the desired speech rate.
-     */
     pub fn set_rate(&mut self, rate: f32) -> Result<&Self, Error> {
         let Features {
             rate: rate_feature, ..
         } = self.supported_features();
         if rate_feature {
-            if rate < self.0.min_rate() || rate > self.0.max_rate() {
+            let mut backend = self.0.write().unwrap();
+            if rate < backend.min_rate() || rate > backend.max_rate() {
                 Err(Error::OutOfRange)
             } else {
-                self.0.set_rate(rate)?;
+                backend.set_rate(rate)?;
                 Ok(self)
             }
         } else {
@@ -350,52 +431,43 @@ impl Tts {
         }
     }
 
-    /**
+    /// Returns the minimum pitch for this speech synthesizer.
-     * Returns the minimum pitch for this speech synthesizer.
-     */
     pub fn min_pitch(&self) -> f32 {
-        self.0.min_pitch()
+        self.0.read().unwrap().min_pitch()
     }
 
-    /**
+    /// Returns the maximum pitch for this speech synthesizer.
-     * Returns the maximum pitch for this speech synthesizer.
-     */
     pub fn max_pitch(&self) -> f32 {
-        self.0.max_pitch()
+        self.0.read().unwrap().max_pitch()
     }
 
-    /**
+    /// Returns the normal pitch for this speech synthesizer.
-     * Returns the normal pitch for this speech synthesizer.
-     */
     pub fn normal_pitch(&self) -> f32 {
-        self.0.normal_pitch()
+        self.0.read().unwrap().normal_pitch()
     }
 
-    /**
+    /// Gets the current speech pitch.
-     * Gets the current speech pitch.
-     */
     pub fn get_pitch(&self) -> Result<f32, Error> {
         let Features { pitch, .. } = self.supported_features();
         if pitch {
-            self.0.get_pitch()
+            self.0.read().unwrap().get_pitch()
         } else {
             Err(Error::UnsupportedFeature)
         }
     }
 
-    /**
+    /// Sets the desired speech pitch.
-     * Sets the desired speech pitch.
-     */
     pub fn set_pitch(&mut self, pitch: f32) -> Result<&Self, Error> {
         let Features {
             pitch: pitch_feature,
             ..
         } = self.supported_features();
         if pitch_feature {
-            if pitch < self.0.min_pitch() || pitch > self.0.max_pitch() {
+            let mut backend = self.0.write().unwrap();
+            if pitch < backend.min_pitch() || pitch > backend.max_pitch() {
                 Err(Error::OutOfRange)
             } else {
-                self.0.set_pitch(pitch)?;
+                backend.set_pitch(pitch)?;
                 Ok(self)
             }
         } else {
@@ -403,52 +475,43 @@ impl Tts {
         }
     }
 
-    /**
+    /// Returns the minimum volume for this speech synthesizer.
-     * Returns the minimum volume for this speech synthesizer.
-     */
     pub fn min_volume(&self) -> f32 {
-        self.0.min_volume()
+        self.0.read().unwrap().min_volume()
     }
 
-    /**
+    /// Returns the maximum volume for this speech synthesizer.
-     * Returns the maximum volume for this speech synthesizer.
-     */
     pub fn max_volume(&self) -> f32 {
-        self.0.max_volume()
+        self.0.read().unwrap().max_volume()
     }
 
-    /**
+    /// Returns the normal volume for this speech synthesizer.
-     * Returns the normal volume for this speech synthesizer.
-     */
     pub fn normal_volume(&self) -> f32 {
-        self.0.normal_volume()
+        self.0.read().unwrap().normal_volume()
     }
 
-    /**
+    /// Gets the current speech volume.
-     * Gets the current speech volume.
-     */
     pub fn get_volume(&self) -> Result<f32, Error> {
         let Features { volume, .. } = self.supported_features();
         if volume {
-            self.0.get_volume()
+            self.0.read().unwrap().get_volume()
         } else {
             Err(Error::UnsupportedFeature)
         }
     }
 
-    /**
+    /// Sets the desired speech volume.
-     * Sets the desired speech volume.
-     */
     pub fn set_volume(&mut self, volume: f32) -> Result<&Self, Error> {
         let Features {
             volume: volume_feature,
             ..
         } = self.supported_features();
         if volume_feature {
-            if volume < self.0.min_volume() || volume > self.0.max_volume() {
+            let mut backend = self.0.write().unwrap();
+            if volume < backend.min_volume() || volume > backend.max_volume() {
                 Err(Error::OutOfRange)
             } else {
-                self.0.set_volume(volume)?;
+                backend.set_volume(volume)?;
                 Ok(self)
             }
         } else {
@@ -456,21 +519,50 @@ impl Tts {
         }
     }
 
-    /**
+    /// Returns whether this speech synthesizer is speaking.
-     * 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()
+            self.0.read().unwrap().is_speaking()
         } else {
             Err(Error::UnsupportedFeature)
         }
     }
 
-    /**
+    /// Returns list of available voices.
-     * Called when this speech synthesizer begins speaking an utterance.
+    pub fn voices(&self) -> Result<Vec<Voice>, Error> {
-     */
+        let Features { voice, .. } = self.supported_features();
+        if voice {
+            self.0.read().unwrap().voices()
+        } else {
+            Err(Error::UnsupportedFeature)
+        }
+    }
+
+    /// Return the current speaking voice.
+    pub fn voice(&self) -> Result<Option<Voice>, Error> {
+        let Features { get_voice, .. } = self.supported_features();
+        if get_voice {
+            self.0.read().unwrap().voice()
+        } else {
+            Err(Error::UnsupportedFeature)
+        }
+    }
+
+    /// Set speaking voice.
+    pub fn set_voice(&mut self, voice: &Voice) -> Result<(), Error> {
+        let Features {
+            voice: voice_feature,
+            ..
+        } = self.supported_features();
+        if voice_feature {
+            self.0.write().unwrap().set_voice(voice)
+        } else {
+            Err(Error::UnsupportedFeature)
+        }
+    }
+
+    /// Called when this speech synthesizer begins speaking an utterance.
     pub fn on_utterance_begin(
         &self,
         callback: Option<Box<dyn FnMut(UtteranceId)>>,
@@ -481,7 +573,7 @@ impl Tts {
         } = self.supported_features();
         if utterance_callbacks {
             let mut callbacks = CALLBACKS.lock().unwrap();
-            let id = self.0.id().unwrap();
+            let id = self.0.read().unwrap().id().unwrap();
             let mut callbacks = callbacks.get_mut(&id).unwrap();
             callbacks.utterance_begin = callback;
             Ok(())
@@ -490,9 +582,7 @@ impl Tts {
         }
     }
 
-    /**
+    /// Called when this speech synthesizer finishes speaking an utterance.
-     * Called when this speech synthesizer finishes speaking an utterance.
-     */
     pub fn on_utterance_end(
         &self,
         callback: Option<Box<dyn FnMut(UtteranceId)>>,
@@ -503,7 +593,7 @@ impl Tts {
         } = self.supported_features();
         if utterance_callbacks {
             let mut callbacks = CALLBACKS.lock().unwrap();
-            let id = self.0.id().unwrap();
+            let id = self.0.read().unwrap().id().unwrap();
             let mut callbacks = callbacks.get_mut(&id).unwrap();
             callbacks.utterance_end = callback;
             Ok(())
@@ -512,9 +602,7 @@ impl Tts {
         }
     }
 
-    /**
+    /// Called when this speech synthesizer is stopped and still has utterances in its queue.
-     * Called when this speech synthesizer is stopped and still has utterances in its queue.
-     */
     pub fn on_utterance_stop(
         &self,
         callback: Option<Box<dyn FnMut(UtteranceId)>>,
@@ -525,7 +613,7 @@ impl Tts {
         } = self.supported_features();
         if utterance_callbacks {
             let mut callbacks = CALLBACKS.lock().unwrap();
-            let id = self.0.id().unwrap();
+            let id = self.0.read().unwrap().id().unwrap();
             let mut callbacks = callbacks.get_mut(&id).unwrap();
             callbacks.utterance_stop = callback;
             Ok(())
@@ -555,9 +643,43 @@ impl Tts {
 
 impl Drop for Tts {
     fn drop(&mut self) {
-        if let Some(id) = self.0.id() {
+        if Arc::strong_count(&self.0) <= 1 {
+            if let Some(id) = self.0.read().unwrap().id() {
                 let mut callbacks = CALLBACKS.lock().unwrap();
                 callbacks.remove(&id);
             }
         }
     }
+}
+
+#[derive(Clone, Copy, Debug, PartialEq, Eq, PartialOrd, Ord, Hash)]
+pub enum Gender {
+    Male,
+    Female,
+}
+
+#[derive(Clone, Debug, PartialEq, Eq, PartialOrd, Ord, Hash)]
+pub struct Voice {
+    pub(crate) id: String,
+    pub(crate) name: String,
+    pub(crate) gender: Option<Gender>,
+    pub(crate) language: LanguageIdentifier,
+}
+
+impl Voice {
+    pub fn id(&self) -> String {
+        self.id.clone()
+    }
+
+    pub fn name(&self) -> String {
+        self.name.clone()
+    }
+
+    pub fn gender(&self) -> Option<Gender> {
+        self.gender
+    }
+
+    pub fn language(&self) -> LanguageIdentifier {
+        self.language.clone()
+    }
+}