Fix QObject segfaults in QML

CURA-6599

cura/Machines/QualityChangesGroup.py

@@ -15,6 +15,14 @@ class QualityChangesGroup(QObject):
 
     def __init__(self, name: str, quality_type: str, intent_category: str, parent: Optional["QObject"] = None) -> None:
         super().__init__(parent)
+
+        # CURA-6599
+        # For some reason, QML will get null or fail to convert type for MachineManager.activeQualityChangesGroup() to
+        # a QObject. Setting the object ownership to QQmlEngine.CppOwnership doesn't work, but setting the object
+        # parent to application seems to work.
+        from cura.CuraApplication import CuraApplication
+        self.setParent(CuraApplication.getInstance())
+
         self.name = name
         self.quality_type = quality_type
         self.intent_category = intent_category

cura/Machines/QualityGroup.py

@@ -26,8 +26,17 @@ from cura.Machines.ContainerNode import ContainerNode
 #
 class QualityGroup(QObject):
 
-    def __init__(self, name: str, quality_type: str, parent = None) -> None:
+    def __init__(self, name: str, quality_type: str, parent: Optional["QObject"] = None) -> None:
         super().__init__(parent)
+
+        # CURA-6599
+        # Same as QualityChangesGroup.
+        # For some reason, QML will get null or fail to convert type for MachineManager.activeQualityChangesGroup() to
+        # a QObject. Setting the object ownership to QQmlEngine.CppOwnership doesn't work, but setting the object
+        # parent to application seems to work.
+        from cura.CuraApplication import CuraApplication
+        self.setParent(CuraApplication.getInstance())
+
         self.name = name
         self.node_for_global = None  # type: Optional[ContainerNode]
         self.nodes_for_extruders = {}  # type: Dict[int, ContainerNode]

cura/Settings/MachineManager.py

@@ -1599,12 +1599,17 @@ class MachineManager(QObject):
     @pyqtProperty(QObject, fset = setQualityChangesGroup, notify = activeQualityChangesGroupChanged)
     def activeQualityChangesGroup(self) -> Optional["QualityChangesGroup"]:
         global_stack = cura.CuraApplication.CuraApplication.getInstance().getGlobalContainerStack()
-        if not global_stack or global_stack.qualityChanges == empty_quality_changes_container:
+        if global_stack is None or global_stack.qualityChanges == empty_quality_changes_container:
             return None
-        for group in ContainerTree.getInstance().getCurrentQualityChangesGroups():  # Match on the container ID of the global stack to find the quality changes group belonging to the active configuration.
+
+        all_group_list = ContainerTree.getInstance().getCurrentQualityChangesGroups()
+        the_group = None
+        for group in all_group_list:  # Match on the container ID of the global stack to find the quality changes group belonging to the active configuration.
             if group.metadata_for_global and group.metadata_for_global["id"] == global_stack.qualityChanges.getId():
-                return group
-        return None
+                the_group = group
+                break
+
+        return the_group
 
     @pyqtProperty(bool, notify = activeQualityChangesGroupChanged)
     def hasCustomQuality(self) -> bool:

resources/qml/PrintSetupSelector/Custom/QualitiesWithIntentMenu.qml

@@ -172,7 +172,16 @@ Popup
                         checkable: true
                         visible: model.available
                         text: model.name
-                        checked: Cura.MachineManager.activeQualityChangesGroup.getName() == model.quality_changes_group.getName()
+                        checked:
+                        {
+                            var active_quality_group = Cura.MachineManager.activeQualityChangesGroup
+
+                            if (active_quality_group != null)
+                            {
+                                return active_quality_group.getName() == model.quality_changes_group.getName()
+                            }
+                            return false
+                        }
                         ButtonGroup.group: buttonGroup
                     }
                 }