Handle empty hotend and material in config syncing

CURA-5693

 - Disable an extruder if the config states no material or nozzle for
   it.
 - Show a warning message if an used extruder gets disabled.

cura/Settings/ExtrudersModel.py

@@ -107,17 +107,19 @@ class ExtrudersModel(UM.Qt.ListModel.ListModel):
     #   that signal. Application.globalContainerStackChanged doesn't fill this
     #   signal; it's assumed to be the current printer in that case.
     def _extrudersChanged(self, machine_id = None):
+        machine_manager = Application.getInstance().getMachineManager()
         if machine_id is not None:
-            if Application.getInstance().getGlobalContainerStack() is None:
+            if machine_manager.activeMachine is None:
                 # No machine, don't need to update the current machine's extruders
                 return
-            if machine_id != Application.getInstance().getGlobalContainerStack().getId():
+            if machine_id != machine_manager.activeMachine.getId():
                 # Not the current machine
                 return
 
         # Unlink from old extruders
         for extruder in self._active_machine_extruders:
             extruder.containersChanged.disconnect(self._onExtruderStackContainersChanged)
+            extruder.enabledChanged.disconnect(self._updateExtruders)
 
         # Link to new extruders
         self._active_machine_extruders = []
@@ -126,6 +128,7 @@ class ExtrudersModel(UM.Qt.ListModel.ListModel):
             if extruder is None: #This extruder wasn't loaded yet. This happens asynchronously while this model is constructed from QML.
                 continue
             extruder.containersChanged.connect(self._onExtruderStackContainersChanged)
+            extruder.enabledChanged.connect(self._updateExtruders)
             self._active_machine_extruders.append(extruder)
 
         self._updateExtruders()  # Since the new extruders may have different properties, update our own model.

cura/Settings/MachineManager.py

@@ -117,10 +117,6 @@ class MachineManager(QObject):
 
         self._application.callLater(self.setInitialActiveMachine)
 
-        self._material_incompatible_message = Message(catalog.i18nc("@info:status",
-                                                "The selected material is incompatible with the selected machine or configuration."),
-                                                title = catalog.i18nc("@info:title", "Incompatible Material"))  # type: Message
-
         containers = CuraContainerRegistry.getInstance().findInstanceContainers(id = self.activeMaterialId)  # type: List[InstanceContainer]
         if containers:
             containers[0].nameChanged.connect(self._onMaterialNameChanged)
@@ -1369,25 +1365,47 @@ class MachineManager(QObject):
         self.blurSettings.emit()
         with postponeSignals(*self._getContainerChangedSignals(), compress = CompressTechnique.CompressPerParameterValue):
             self.switchPrinterType(configuration.printerType)
+
+            used_extruder_stack_list = ExtruderManager.getInstance().getUsedExtruderStacks()
+            used_extruder_position_set = {es.getMetaDataEntry("position") for es in used_extruder_stack_list}
+            disabled_used_extruder_position_set = set()
+
+            # If an extruder that's currently used to print a model gets disabled due to the syncing, we need to show
+            # a message explaining why.
+            need_to_show_message = False
+
             for extruder_configuration in configuration.extruderConfigurations:
                 position = str(extruder_configuration.position)
-                variant_container_node = self._variant_manager.getVariantNode(self._global_container_stack.definition.getId(), extruder_configuration.hotendID)
-                material_container_node = self._material_manager.getMaterialNodeByType(self._global_container_stack,
-                                                                                       position,
-                                                                                       extruder_configuration.hotendID,
-                                                                                       configuration.buildplateConfiguration,
-                                                                                       extruder_configuration.material.guid)
 
-                if variant_container_node:
+                extruder_has_hotend = extruder_configuration.hotendID != ""
-                    self._setVariantNode(position, variant_container_node)
+                extruder_has_material = extruder_configuration.material.guid != ""
-                else:
+
-                    self._global_container_stack.extruders[position].variant = empty_variant_container
+                # If the machine doesn't have a hotend or material, disable this extruder
+                if not extruder_has_hotend or not extruder_has_material:
+                    self._global_container_stack.extruders[position].setEnabled(False)
+                    if position in used_extruder_position_set:
+                        need_to_show_message = True
+                        disabled_used_extruder_position_set.add(int(position))
 
-                if material_container_node:
-                    self._setMaterial(position, material_container_node)
                 else:
-                    self._global_container_stack.extruders[position].material = empty_material_container
+                    variant_container_node = self._variant_manager.getVariantNode(self._global_container_stack.definition.getId(),
-                self.updateMaterialWithVariant(position)
+                                                                                  extruder_configuration.hotendID)
+                    material_container_node = self._material_manager.getMaterialNodeByType(self._global_container_stack,
+                                                                                           position,
+                                                                                           extruder_configuration.hotendID,
+                                                                                           configuration.buildplateConfiguration,
+                                                                                           extruder_configuration.material.guid)
+                    if variant_container_node:
+                        self._setVariantNode(position, variant_container_node)
+                    else:
+                        self._global_container_stack.extruders[position].variant = empty_variant_container
+
+                    if material_container_node:
+                        self._setMaterial(position, material_container_node)
+                    else:
+                        self._global_container_stack.extruders[position].material = empty_material_container
+                    self._global_container_stack.extruders[position].setEnabled(True)
+                    self.updateMaterialWithVariant(position)
 
             if configuration.buildplateConfiguration is not None:
                 global_variant_container_node = self._variant_manager.getBuildplateVariantNode(self._global_container_stack.definition.getId(), configuration.buildplateConfiguration)
@@ -1399,6 +1417,14 @@ class MachineManager(QObject):
                 self._global_container_stack.variant = empty_variant_container
             self._updateQualityWithMaterial()
 
+            if need_to_show_message:
+                msg_str = "Extruder {extruders} is disabled because there is no material loaded. Please load a material or use custom configurations."
+                extruders_str = ", ".join(str(x) for x in sorted(disabled_used_extruder_position_set))
+                msg_str = msg_str.format(extruders = extruders_str)
+                message = Message(catalog.i18nc("@info:status", msg_str),
+                                  title = catalog.i18nc("@info:title", "Extruders Disabled"))
+                message.show()
+
         # See if we need to show the Discard or Keep changes screen
         if self.hasUserSettings and self._application.getPreferences().getValue("cura/active_mode") == 1:
             self._application.discardOrKeepProfileChanges()