Update the sync-storage path every time you sync

Instead of updating the storage path every time you add or remove a removable drive, we now update the storage path every time you press the button to sync. That way this detail has no impact on performance of other parts of Cura if they don't use this button. It also makes the code a bit simpler.
The only downside is that this FileDialog then contains state, instead of automatically syncing with the MaterialManagement property for its folder property. I see that as a lesser of two evils.

Contributes to issue CURA-8055.

cura/Machines/Models/MaterialManagementModel.py

@@ -21,16 +21,6 @@ if TYPE_CHECKING:
 catalog = i18nCatalog("cura")
 
 class MaterialManagementModel(QObject):
-    """Proxy class to the materials page in the preferences.
-
-    This class handles the actions in that page, such as creating new materials, renaming them, etc.
-    """
-    def __init__(self, parent: QObject) -> None:
-        super().__init__(parent)
-        cura_application = cura.CuraApplication.CuraApplication.getInstance()
-        self._preferred_export_all_path = None  # type: Optional[QUrl]  # Path to export all materials to. None if not yet initialised.
-        cura_application.getOutputDeviceManager().outputDevicesChanged.connect(self._onOutputDevicesChanged)
-
     favoritesChanged = pyqtSignal(str)
     """Triggered when a favorite is added or removed.
 
@@ -271,25 +261,8 @@ class MaterialManagementModel(QObject):
         except ValueError:  # Material was not in the favorites list.
             Logger.log("w", "Material {material_base_file} was already not a favorite material.".format(material_base_file = material_base_file))
 
-    def _onOutputDevicesChanged(self) -> None:
-        """
-        When the list of output devices changes, we may want to update the
-        preferred export path.
-        """
-        cura_application = cura.CuraApplication.CuraApplication.getInstance()
-        device_manager = cura_application.getOutputDeviceManager()
-        devices = device_manager.getOutputDevices()
-        for device in devices:
-            if device.__class__.__name__ == "RemovableDriveOutputDevice":
-                self._preferred_export_all_path = QUrl.fromLocalFile(device.getId())
-                break
-        else:  # No removable drives? Use local path.
-            self._preferred_export_all_path = cura_application.getDefaultPath("dialog_material_path")
-        self.outputDevicesChanged.emit()
-
-    outputDevicesChanged = pyqtSignal()  # Triggered when adding or removing removable drives.
-    @pyqtProperty(QUrl, notify = outputDevicesChanged)
-    def preferredExportAllPath(self) -> QUrl:
+    @pyqtSlot(result = QUrl)
+    def getPreferredExportAllPath(self) -> QUrl:
         """
         Get the preferred path to export materials to.
 
@@ -297,9 +270,14 @@ class MaterialManagementModel(QObject):
         file path.
         :return: The preferred path to export all materials to.
         """
-        if self._preferred_export_all_path is None:  # Not initialised yet. Can happen when output devices changed before class got created.
-            self._onOutputDevicesChanged()
-        return self._preferred_export_all_path
+        cura_application = cura.CuraApplication.CuraApplication.getInstance()
+        device_manager = cura_application.getOutputDeviceManager()
+        devices = device_manager.getOutputDevices()
+        for device in devices:
+            if device.__class__.__name__ == "RemovableDriveOutputDevice":
+                return QUrl.fromLocalFile(device.getId())
+        else:  # No removable drives? Use local path.
+            return cura_application.getDefaultPath("dialog_material_path")
 
     @pyqtSlot(QUrl)
     def exportAll(self, file_path: QUrl) -> None:

resources/qml/Preferences/Materials/MaterialsPage.qml

@@ -201,6 +201,7 @@ Item
             onClicked:
             {
                 forceActiveFocus();
+                exportAllMaterialsDialog.folder = base.materialManagementModel.getPreferredExportAllPath();
                 exportAllMaterialsDialog.open();
             }
             visible: Cura.MachineManager.activeMachine.supportsMaterialExport
@@ -388,7 +389,6 @@ Item
         title: catalog.i18nc("@title:window", "Export All Materials")
         selectExisting: false
         nameFilters: ["Material archives (*.umm)", "All files (*)"]
-        folder: base.materialManagementModel.preferredExportAllPath
         onAccepted:
         {
             base.materialManagementModel.exportAll(fileUrl);