support configuration of audio backend and backend device

fixes #194

README.md

@@ -122,6 +122,8 @@ values are:
 
 * `use_nerdfont`: Turn nerdfont glyphs on/off <true/false>
 * `theme`: Set a custom color palette (see below)
+* `backend`: Audio backend to use, run `ncspot -h` for a list of devices
+* `backend_device`: Audio device string to configure the backend
 * `audio_cache`: Enable or disable caching of audio files, on by default
   <true/false>
 * `volnorm`: Enable or disable volume normalization, off by default <true/false>

src/config.rs

@@ -14,6 +14,8 @@ pub struct Config {
     pub use_nerdfont: Option<bool>,
     pub saved_state: Option<SavedState>,
     pub audio_cache: Option<bool>,
+    pub backend: Option<String>,
+    pub backend_device: Option<String>,
     pub volnorm: Option<bool>,
     pub volnorm_pregain: Option<f32>,
 }

src/main.rs

@@ -49,6 +49,7 @@ use cursive::Cursive;
 
 use librespot_core::authentication::Credentials;
 use librespot_core::cache::Cache;
+use librespot_playback::audio_backend;
 
 mod album;
 mod artist;
@@ -121,10 +122,15 @@ fn credentials_prompt(reset: bool) -> Credentials {
 }
 
 fn main() {
+    let backends = {
+        let backends: Vec<&str> = audio_backend::BACKENDS.iter().map(|b| b.0).collect();
+        format!("Audio backends: {}", backends.join(", "))
+    };
     let matches = App::new("ncspot")
         .version(env!("CARGO_PKG_VERSION"))
         .author("Henrik Friedrichsen <henrik@affekt.org> and contributors")
         .about("cross-platform ncurses Spotify client")
+        .after_help(&*backends)
         .arg(
             Arg::with_name("debug")
                 .short("d")

src/spotify.rs

@@ -373,12 +373,12 @@ impl Spotify {
         let mixer = create_mixer(None);
         mixer.set_volume(volume);
 
-        let backend = audio_backend::find(None).unwrap();
+        let backend = audio_backend::find(cfg.backend.clone()).unwrap();
         let (player, _eventchannel) = Player::new(
             player_config,
             session.clone(),
             mixer.get_audio_filter(),
-            move || (backend)(None),
+            move || (backend)(cfg.backend_device),
         );
 
         let worker = Worker::new(events, commands, session, player, mixer);