Add callback to lock status

docs/lock_status.md

@@ -16,8 +16,38 @@ when the lock is enabled and `False` otherwise.
 
 |Method                    |Description |
 |--------------------------|------------|
-|`locks.get_caps_lock() `  |Num Lock    |
+|`locks.get_num_lock() `   |Num Lock    |
 |`locks.get_caps_lock() `  |Caps Lock   |
 |`locks.get_scroll_lock() `|Scroll Lock |
 |`locks.get_compose() `    |Compose     |
 |`locks.get_kana() `       |Kana        |
+
+
+## React to Lock Status Changes
+Lock Status will accept a callback function that is invoked when the status of
+a lock changes. When the function is invoked, it will have a Lock Status object
+passed to it.
+
+```python
+import board
+
+from kb import KMKKeyboard
+from kmk.extensions.lock_status import LockStatus
+from kmk.extensions.LED import LED
+
+keyboard = KMKKeyboard()
+keyboard.extensions.append(LED(led_pin=[board.GP27, board.GP28]))
+
+def toggle_lock_leds(self):
+    if self.get_caps_lock():
+        keyboard.leds.set_brightness(50, leds=[0])
+    else:
+        keyboard.leds.set_brightness(0, leds=[0])
+
+    if self.get_scroll_lock():
+        keyboard.leds.set_brightness(50, leds=[1])
+    else:
+        keyboard.leds.set_brightness(0, leds=[1])
+
+keyboard.extensions.append(LockStatus(toggle_lock_leds))
+```

kmk/extensions/lock_status.py

@@ -14,12 +14,14 @@ class LockCode:
 
 
 class LockStatus(Extension):
-    def __init__(self):
-        self.report = 0x00
+    def __init__(self, fn=None):
+        self.report = None
         self.hid = None
+        self.fn = fn
         for device in usb_hid.devices:
             if device.usage == HIDUsage.KEYBOARD:
                 self.hid = device
+                self.hid.get_last_received_report()
 
     def __repr__(self):
         return f'LockStatus(report={self.report})'
@@ -41,6 +43,8 @@ class LockStatus(Extension):
             report = self.hid.get_last_received_report()
             if report[0] != self.report:
                 self.report = report[0]
+                if self.fn:
+                    self.fn(self)
         return
 
     def on_powersave_enable(self, sandbox):
@@ -62,4 +66,4 @@ class LockStatus(Extension):
         return bool(self.report & LockCode.COMPOSE)
 
     def get_kana(self):
-        return bool(self.report & LockCode.KANA)
+        return bool(self.report & LockCode.KANA)