implements scanner with rotaryio

docs/scanners.md

@@ -99,6 +99,7 @@ class MyKeyboard(KMKKeyboard):
         )
 ```
 
+
 ## Digitalio Scanners
 
 ### digitalio MatrixScanner
@@ -120,6 +121,28 @@ class MyKeyboard(KMKKeyboard):
         )
 ```
 
+
+## Rotary Encoder Scanners
+
+### RotaryioEncoder
+
+Matrix events from a quadrature ("rotary") encoder?
+
+```python
+from kmk.scanners.encoder import RotaryioEncoder
+
+class MyKeyboard(KMKKeyboard):
+    def __init__(self):
+        # create and register the scanner
+        self.matrix = RotaryioEncoder(
+            pin_a=board.GP0,
+            pin_b=board.GP1,
+            # optional
+            divisor=4,
+        )
+```
+
+
 ## `Scanner` base class
 
 If you require a different type of scanner, you can create your own by

kmk/scanners/encoder.py

@@ -0,0 +1,43 @@
+import keypad
+import rotaryio
+
+from kmk.scanners import Scanner
+
+
+class RotaryioEncoder(Scanner):
+    def __init__(self, pin_a, pin_b, divisor=4):
+        self.encoder = rotaryio.IncrementalEncoder(pin_a, pin_b, divisor)
+        self.position = 0
+        self._pressed = False
+        self._queue = []
+
+    @property
+    def key_count(self):
+        return 2
+
+    def scan_for_changes(self):
+        position = self.encoder.position
+
+        if position != self.position:
+            self._queue.append(position - self.position)
+            self.position = position
+
+        if not self._queue:
+            return
+
+        key_number = self.offset
+        if self._queue[0] > 0:
+            key_number += 1
+
+        if self._pressed:
+            self._queue[0] -= 1 if self._queue[0] > 0 else -1
+
+            if self._queue[0] == 0:
+                self._queue.pop(0)
+
+            self._pressed = False
+
+        else:
+            self._pressed = True
+
+        return keypad.Event(key_number, self._pressed)