Events: Add Play/Pause events.

Uses much of the existing machinery to add some more PlayMode state change events—all in all, a pretty simple change.

Closes #29.

src/driver/tasks/events.rs

@@ -70,8 +70,8 @@ pub(crate) async fn runner(_interconnect: Interconnect, evt_rx: Receiver<EventMe
                     Mode(mode) => {
                         let old = state.playing;
                         state.playing = mode;
-                        if old != mode && mode.is_done() {
+                        if old != mode {
-                            global.fire_track_event(TrackEvent::End, i);
+                            global.fire_track_event(mode.as_track_event(), i);
                         }
                     },
                     Volume(vol) => {

src/events/track.rs

@@ -10,6 +10,14 @@
 #[derive(Clone, Copy, Debug, Eq, Hash, PartialEq)]
 #[non_exhaustive]
 pub enum TrackEvent {
+    /// The attached track has resumed playing.
+    ///
+    /// This event will not fire when a track first starts,
+    /// but will fire when a track changes from, e.g., paused to playing.
+    /// This is most relevant for queue users.
+    Play,
+    /// The attached track has been paused.
+    Pause,
     /// The attached track has ended.
     End,
     /// The attached track has looped.

src/tracks/mode.rs

@@ -1,3 +1,5 @@
+use crate::events::TrackEvent;
+
 /// Playback status of a track.
 #[derive(Clone, Copy, Debug, Eq, PartialEq)]
 #[non_exhaustive]
@@ -29,6 +31,15 @@ impl PlayMode {
             state => state,
         }
     }
+
+    pub(crate) fn as_track_event(self) -> TrackEvent {
+        use PlayMode::*;
+        match self {
+            Play => TrackEvent::Play,
+            Pause => TrackEvent::Pause,
+            Stop | End => TrackEvent::End,
+        }
+    }
 }
 
 impl Default for PlayMode {