Fix PySide6.8 signal-slot threading problem

Closes #293 (closed)

PySide6.8 includes a rewrite of the signal-thread code. One of the side-effects is that the thread affinity (i.e. the thread a slot runs in) of a function slot is changed. Before, a function slot defaults to running in the main thread. In 6.8, a function slots run in the thread in which the signal that invoked it lives. This causes some code which relied on the old behavior to break.

This MR fixes the problem by creating a wrapper class for the problematic function. All instances of the wrapper class are automatically moved to the main thread on creation. Then, whenever the old threading behavior needs to be used, we use the wrapper class instead of using the function directly. Because the function is called from an object in the main thread in this case, it will always run in the main thread, which fixes our problem.

sohstationviewer/model/data_loader.py

@@ -9,7 +9,10 @@ from PySide6.QtCore import Qt
 from PySide6 import QtCore, QtWidgets
 
 from sohstationviewer.conf import constants
-from sohstationviewer.controller.util import display_tracking_info
+from sohstationviewer.controller.util import (
+    display_tracking_info,
+    DisplayTrackingInfoWrapper,
+)
 from sohstationviewer.model.general_data.general_data import (
     GeneralData, ThreadStopped, ProcessingDataError)
 from sohstationviewer.model.reftek_data.reftek_reader.log_file_reader import \
@@ -64,7 +67,11 @@ class DataLoaderWorker(QtCore.QObject):
         # the read. Since self.run runs in a background thread, we need to use
         # signal-slot mechanism to ensure that display_tracking_info runs in
         # the main thread.
-        self.notification.connect(display_tracking_info)
+        self.tracking_info_display = DisplayTrackingInfoWrapper()
+        self.notification.connect(
+            self.tracking_info_display.display_tracking_info,
+            type=Qt.ConnectionType.QueuedConnection
+        )
         self.end_msg = None
         # to change display tracking info to error when failed
         self.process_failed: bool = False

[Lan Dam]

Do we need self. here?

[Kien Le]

Probably not? I added it just in case the reference to the method is garbage collected. I have encountered this kind of issue before where an object gets deleted if they are not saved as an instance attribute.