don't send event when value doesn't change

owrx/property/__init__.py

@@ -182,12 +182,12 @@ class PropertyStack(PropertyManager):
 
     def replaceLayer(self, priority: int, pm: PropertyManager):
         layers = [x for x in self.layers if x["priority"] == priority]
-        changes = {}
-        if layers:
-            changes = self._removeLayer(layers[0])
 
-        for k, v in self._addLayer(priority, pm).items():
-            changes[k] = v
+        originalState = self.__dict__()
+
+        changes = self._removeLayer(layers[0]) if layers else {}
+        changes = {**changes, **self._addLayer(priority, pm)}
+        changes = {k: v for k, v in changes.items() if k not in originalState or originalState[k] != v}
 
         self._fireChanges(changes)
 

test/property/test_property_stack.py

@@ -167,3 +167,21 @@ class PropertyStackTest(TestCase):
 
         layer["testkey"] = "after"
         mock.method.assert_not_called()
+
+    def testReplaceLayerNoEventWhenValueUnchanged(self):
+        fixed = PropertyLayer()
+        fixed["testkey"] = "fixed value"
+        first_layer = PropertyLayer()
+        first_layer["testkey"] = "same value"
+        second_layer = PropertyLayer()
+        second_layer["testkey"] = "same value"
+
+        stack = PropertyStack()
+        stack.addLayer(1, fixed)
+        stack.addLayer(0, first_layer)
+        mock = Mock()
+        stack.wire(mock.method)
+        mock.method.assert_not_called()
+
+        stack.replaceLayer(0, second_layer)
+        mock.method.assert_not_called()