Merge pull request #91 from hsorby/main

Fix issue with MRO not working when multiple inheritance involving C++ classes.

Author: hsorby

src/cmlibs/widgets/basesceneviewerwidget.py

@@ -39,6 +39,10 @@ def __init__(self, parent=None):
         Initialise other attributes that deal with selection and the rotation of the plane.
         """
         super().__init__(parent)
+        # For some (older) versions of Python, the QOpenGLWidget (or subclass) does not call super().__init(parent),
+        # this causes the MRO to not include the InteractionManager class __init__ function call.
+        # So we must call the InteractionManager __init__ function manually to set up the interaction handlers.
+        InteractionManager.__init__(self)
         # Create a Zinc context from which all other objects can be derived either directly or indirectly.
         self._graphics_initialized = False
         self._context = None

src/cmlibs/widgets/handlers/interactionmanager.py

@@ -6,6 +6,7 @@ class InteractionManager:
     handler_deactivated = QtCore.Signal()
 
     def __init__(self, *args, **kwargs):
+        super().__init__()
         self._handlers = {}
         self._key_code_handler_map = {}
         self._active_handler = None