WIP: Make MachineSetting panel work

cura/UI/MachineSettingsManager.py

@@ -0,0 +1,66 @@
+
+from typing import Any, Dict, Optional, TYPE_CHECKING
+
+from PyQt5.QtCore import Qt, QObject, pyqtSlot
+
+from UM.i18n import i18nCatalog
+
+
+class MachineSettingsManager(QObject):
+
+    def __init__(self, parent: Optional["QObject"] = None) -> None:
+        super().__init__(parent)
+        self._i18n_catalog = i18nCatalog("cura")
+
+        from cura.CuraApplication import CuraApplication
+        self._application = CuraApplication.getInstance()
+
+    # Force rebuilding the build volume by reloading the global container stack. This is a bit of a hack, but it seems
+    # quite enough.
+    @pyqtSlot()
+    def forceUpdate(self) -> None:
+        self._application.getMachineManager().globalContainerChanged.emit()
+
+    # Function for the Machine Settings panel (QML) to update the compatible material diameter after a user has changed
+    # an extruder's compatible material diameter. This ensures that after the modification, changes can be notified
+    # and updated right away.
+    @pyqtSlot(int)
+    def updateMaterialForDiameter(self, extruder_position: int):
+        # Updates the material container to a material that matches the material diameter set for the printer
+        self._application.getMachineManager().updateMaterialWithVariant(str(extruder_position))
+
+    # FIXME(Lipu): Better document what this function does, especially the fuzzy gcode flavor and has_materials logic
+    #              regarding UM2 and UM2+
+    # Function for the Machine Settings panel (QML) to update after the usre changes "Number of Extruders".
+    @pyqtSlot()
+    def updateHasMaterialsMetadata(self):
+        machine_manager = self._application.getMachineManager()
+        material_manager = self._application.getMaterialManager()
+
+        global_stack = material_manager.activeMachine
+
+        definition = global_stack.definition
+        if definition.getProperty("machine_gcode_flavor", "value") != "UltiGCode" or definition.getMetaDataEntry(
+                "has_materials", False):
+            # In other words: only continue for the UM2 (extended), but not for the UM2+
+            return
+
+        extruder_positions = list(global_stack.extruders.keys())
+        has_materials = global_stack.getProperty("machine_gcode_flavor", "value") != "UltiGCode"
+
+        material_node = None
+        if has_materials:
+            global_stack.setMetaDataEntry("has_materials", True)
+        else:
+            # The metadata entry is stored in an ini, and ini files are parsed as strings only.
+            # Because any non-empty string evaluates to a boolean True, we have to remove the entry to make it False.
+            if "has_materials" in global_stack.getMetaData():
+                global_stack.removeMetaDataEntry("has_materials")
+
+        # set materials
+        for position in extruder_positions:
+            if has_materials:
+                material_node = material_manager.getDefaultMaterial(global_stack, position, None)
+            machine_manager.setMaterial(position, material_node)
+
+        self.forceUpdate()