Propagate whether mouse release handler handles event

Propagate further the result of the mouse release handler, and made sure that if a handler had successfully handled the event to set the correct flag on the event to stop Qt re-raising it to one element further up in the display heirarchy.

nion/ui/PyQtProxy.py

@@ -2112,7 +2112,9 @@ def mouseReleaseEvent(self, event: QtGui.QMouseEvent) -> None:
         if self.object and event.button() == QtCore.Qt.LeftButton:
             display_scaling = GetDisplayScaling()
             try:
-                self.object.mouseReleased(event.position().x() // display_scaling, event.position().y() // display_scaling, event.modifiers().value)
+                result = self.object.mouseReleased(event.position().x() // display_scaling, event.position().y() // display_scaling, event.modifiers().value)
+                if result:
+                    event.accept()
             except Exception as e:
                 import traceback
                 traceback.print_exc()

nion/ui/QtUserInterface.py

@@ -1659,10 +1659,10 @@ def mousePressed(self, x: int, y: int, raw_modifiers: int) -> None:
         if callable(self.on_mouse_pressed):
             self.on_mouse_pressed(x, y, QtKeyboardModifiers(raw_modifiers))
 
-    def mouseReleased(self, x: int, y: int, raw_modifiers: int) -> None:
+    def mouseReleased(self, x: int, y: int, raw_modifiers: int) -> bool:
         self._register_ui_activity()
         if callable(self.on_mouse_released):
-            self.on_mouse_released(x, y, QtKeyboardModifiers(raw_modifiers))
+            return  self.on_mouse_released(x, y, QtKeyboardModifiers(raw_modifiers))
 
     def mousePositionChanged(self, x: int, y: int, raw_modifiers: int) -> None:
         if callable(self.on_mouse_position_changed):