move callbacks/observer examples into examples/events/

examples/events/observer/README.md

@@ -0,0 +1,14 @@
+## About
+
+Registers a class as an observer and defines a callback.
+
+## Use
+
+Run the script, then:
+
+-   change GUI parameters to trigger pdirty
+-   press any macrobutton to trigger mdirty
+-   play audio through any bus to trigger ldirty
+-   any midi input to trigger midi
+
+Pressing `<Enter>` will exit.

examples/events/observer/__main__.py

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+import logging
+
+import voicemeeterlib
+
+logging.basicConfig(level=logging.INFO)
+
+
+class App:
+    def __init__(self, vm):
+        self._vm = vm
+        # register your app as event observer
+        self._vm.observer.add(self)
+
+    def __str__(self):
+        return type(self).__name__
+
+    # define an 'on_update' callback function to receive event updates
+    def on_update(self, event):
+        if event == 'pdirty':
+            print('pdirty!')
+        elif event == 'mdirty':
+            print('mdirty!')
+        elif event == 'ldirty':
+            for bus in self._vm.bus:
+                if bus.levels.isdirty:
+                    print(bus, bus.levels.all)
+        elif event == 'midi':
+            current = self._vm.midi.current
+            print(f'Value of midi button {current} is {self._vm.midi.get(current)}')
+
+
+def main():
+    KIND_ID = 'banana'
+
+    with voicemeeterlib.api(
+        KIND_ID, **{k: True for k in ('pdirty', 'mdirty', 'ldirty', 'midi')}
+    ) as vm:
+        App(vm)
+
+        while _ := input('Press <Enter> to exit\n'):
+            pass
+
+
+if __name__ == '__main__':
+    main()