Prevent the deletion of materials that are still active

cura/Machines/MaterialManager.py

@@ -553,10 +553,24 @@ class MaterialManager(QObject):
     #
     # Methods for GUI
     #
+    @pyqtSlot("QVariant", result=bool)
+    def canMaterialBeRemoved(self, material_node: "MaterialNode"):
+        # Check if the material is active in any extruder train. In that case, the material shouldn't be removed!
+        # In the future we might enable this again, but right now, it's causing a ton of issues if we do (since it
+        # corrupts the configuration)
+        root_material_id = material_node.getMetaDataEntry("base_file")
+        material_group = self.getMaterialGroup(root_material_id)
+        if not material_group:
+            return False
+
+        nodes_to_remove = [material_group.root_material_node] + material_group.derived_material_node_list
+        ids_to_remove = [node.getMetaDataEntry("id", "") for node in nodes_to_remove]
+
+        for extruder_stack in self._container_registry.findContainerStacks(type="extruder_train"):
+            if extruder_stack.material.getId() in ids_to_remove:
+                return False
+        return True
 
-    #
-    # Sets the new name for the given material.
-    #
     @pyqtSlot("QVariant", str)
     def setMaterialName(self, material_node: "MaterialNode", name: str) -> None:
         root_material_id = material_node.getMetaDataEntry("base_file")

resources/qml/Preferences/Materials/MaterialsPage.qml

@@ -127,7 +127,7 @@ Item
         {
             text: catalog.i18nc("@action:button", "Remove")
             iconName: "list-remove"
-            enabled: base.hasCurrentItem && !base.currentItem.is_read_only && !base.isCurrentItemActivated
+            enabled: base.hasCurrentItem && !base.currentItem.is_read_only && !base.isCurrentItemActivated && base.materialManager.canMaterialBeRemoved(base.currentItem.container_node)
             onClicked:
             {
                 forceActiveFocus();