refactor control and sequencer rendering

src/model/phrase.rs

@@ -3,6 +3,7 @@ use crate::core::*;
 /// Define a MIDI phrase.
 #[macro_export] macro_rules! phrase {
     ($($t:expr => $msg:expr),* $(,)?) => {{
+        #[allow(unused_mut)]
         let mut phrase = BTreeMap::new();
         $(phrase.insert($t, vec![]);)*
         $(phrase.get_mut(&$t).unwrap().push($msg);)*

src/model/track.rs

@@ -124,7 +124,7 @@ impl Track {
         reset:    bool,
         scope:    &ProcessScope,
         (frame0, frames): (usize, usize),
-        (usec0,  usecs):  (usize, usize),
+        (_usec0,  _usecs):  (usize, usize),
         period:   f64,
     ) {
         // Need to be borrowed outside the conditionals?