zero latency debounce

src/keyboard.rs

@@ -78,26 +78,24 @@ impl<KN: AdcChannel<Atmega, ADC>, KO: AdcChannel<Atmega, ADC>> Keyboard<KN, KO>
 pub struct Debounce {
     record: [Option<KeyReadout>; DEBOUNCE_DEPTH],
     pos: usize,
-    last: Option<KeyReadout>,
 }
 
 impl Debounce {
     pub fn input(&mut self, key: Option<KeyReadout>) -> Option<KeyPress> {
+        // React to fresh key press immediately if it was not pressed for depth of record
+        let new_key = key.and_then(|key| {
+            self.record
+                .iter()
+                .all(|hist| hist != &Some(key))
+                .then_some(key)
+        });
+
         self.record[self.pos] = key;
         self.pos += 1;
         if self.pos >= self.record.len() {
             self.pos = 0;
         }
-        if self.record.iter().all(|hist| hist == &key) && self.last != key {
-            self.last = key;
-            key.and_then(|key_readout| {
-                KeyPress::map(key_readout.display_no, key_readout.kn, key_readout.ko)
-            })
-        } else if self.record.iter().all(|hist| hist == &None) {
-            self.last = None;
-            None
-        } else {
-            None
-        }
+
+        new_key.and_then(|key| KeyPress::map(key.display_no, key.kn, key.ko))
     }
 }