wip: refactor pt.41 (57e) nice

crates/tek_api/src/api_playhead.rs

@@ -75,3 +75,39 @@ pub trait PlayheadApi: ClockApi {
         *self.playing().read().unwrap() == Some(TransportState::Rolling)
     }
 }
+
+/// Hosts the JACK callback for updating the temporal pointer and playback status.
+pub struct PlayheadAudio<'a, T: PlayheadApi>(pub &'a mut T);
+
+impl<'a, T: PlayheadApi> Audio for PlayheadAudio<'a, T> {
+    #[inline] fn process (&mut self, _: &Client, scope: &ProcessScope) -> Control {
+        let state = &mut self.0;
+        let times = scope.cycle_times().unwrap();
+        let CycleTimes { current_frames, current_usecs, next_usecs: _, period_usecs: _ } = times;
+        let _chunk_size = scope.n_frames() as usize;
+        let transport = state.transport().query().unwrap();
+        state.current().sample.set(transport.pos.frame() as f64);
+        let mut playing = state.playing().write().unwrap();
+        let mut started = state.started().write().unwrap();
+        if *playing != Some(transport.state) {
+            match transport.state {
+                TransportState::Rolling => {
+                    *started = Some((current_frames as usize, current_usecs as usize))
+                },
+                TransportState::Stopped => {
+                    *started = None
+                },
+                _ => {}
+            }
+        };
+        *playing = Some(transport.state);
+        if *playing == Some(TransportState::Stopped) {
+            *started = None;
+        }
+        state.current().update_from_usec(match *started {
+            Some((_, usecs)) => current_usecs as f64 - usecs as f64,
+            None => 0.
+        });
+        Control::Continue
+    }
+}