Use public activeExtruderIndex rather than internal _activeExtruderIndex

So that this getter still does what it needs to do if we ever decide to add side-effects.

Contributes to issue CURA-5876.

cura/Settings/ExtruderManager.py

@@ -63,7 +63,7 @@ class ExtruderManager(QObject):
         if not self._application.getGlobalContainerStack():
             return None  # No active machine, so no active extruder.
         try:
-            return self._extruder_trains[self._application.getGlobalContainerStack().getId()][str(self._active_extruder_index)].getId()
+            return self._extruder_trains[self._application.getGlobalContainerStack().getId()][str(self.activeExtruderIndex)].getId()
         except KeyError:  # Extruder index could be -1 if the global tab is selected, or the entry doesn't exist if the machine definition is wrong.
             return None
 
@@ -144,7 +144,7 @@ class ExtruderManager(QObject):
 
     @pyqtSlot(result = QObject)
     def getActiveExtruderStack(self) -> Optional["ExtruderStack"]:
-        return self.getExtruderStack(self._active_extruder_index)
+        return self.getExtruderStack(self.activeExtruderIndex)
 
     ##  Get an extruder stack by index
     def getExtruderStack(self, index) -> Optional["ExtruderStack"]:

cura/Settings/MachineManager.py

@@ -866,7 +866,7 @@ class MachineManager(QObject):
             caution_message = Message(catalog.i18nc(
                 "@info:generic",
                 "Settings have been changed to match the current availability of extruders: [%s]" % ", ".join(add_user_changes)),
-                lifetime=0,
+                lifetime = 0,
                 title = catalog.i18nc("@info:title", "Settings updated"))
             caution_message.show()
 

plugins/CuraEngineBackend/ProcessSlicedLayersJob.py

@@ -195,7 +195,7 @@ class ProcessSlicedLayersJob(Job):
         if extruders:
             material_color_map = numpy.zeros((len(extruders), 4), dtype=numpy.float32)
             for extruder in extruders:
-                position = int(extruder.getMetaDataEntry("position", default="0"))  # Get the position
+                position = int(extruder.getMetaDataEntry("position", default = "0"))
                 try:
                     default_color = ExtrudersModel.defaultColors[position]
                 except IndexError: