gattlib/mainloop: Move mainloop to Python to ease support

gattlib-py/gattlib/mainloop.py

@@ -4,8 +4,68 @@
 # Copyright (c) 2016-2024, Olivier Martin <olivier@labapart.org>
 #
 
-from gattlib import *
+import logging
+import threading
+import time
+import traceback
 
-def run_mainloop_with(target):
-    gattlib_mainloop(target, None)
+#import dbus.mainloop.glib
+from gi.repository import GObject
 
+gobject_mainloop: GObject.MainLoop = None
+task_returned_code: int = -1
+task_exception: Exception = None
+
+def _user_thread_main(task):
+    """Main entry point for the thread that will run user's code."""
+    global gobject_mainloop, task_returned_code, task_exception
+
+    try:
+        # Wait for GLib main loop to start running before starting user code.
+        while True:
+            if gobject_mainloop is not None and gobject_mainloop.is_running():
+                # Main loop is running, we should be ready to make bluez DBus calls.
+                break
+            # Main loop isn't running yet, give time back to other threads.
+            time.sleep(0)
+
+        # Run user's code.
+        task_returned_code = task()
+    except Exception as ex:
+        logging.error("Exception in %s: %s: %s", task, type(ex), str(ex))
+        traceback.print_exception(type(ex), ex, ex.__traceback__)
+        task_exception = ex
+    finally:
+        gobject_mainloop.quit()
+
+def run_mainloop_with(task):
+    global gobject_mainloop, task_returned_code, task_exception
+
+    # Ensure GLib's threading is initialized to support python threads, and
+    # make a default mainloop that all DBus objects will inherit.  These
+    # commands MUST execute before any other DBus commands!
+    #GObject.threads_init()
+    #dbus.mainloop.glib.threads_init()
+    # Set the default main loop, this also MUST happen before other DBus calls.
+    #mainloop = dbus.mainloop.glib.DBusGMainLoop(set_as_default=True)
+
+    # Create a background thread to run the user task
+    user_thread = threading.Thread(target=_user_thread_main, name="gattlib-task", args=(task,))
+    user_thread.start()
+
+    # Spin up a GLib main loop in the main thread to process async BLE events.
+    gobject_mainloop = GObject.MainLoop()
+    try:
+        gobject_mainloop.run()  # Doesn't return until the mainloop ends.
+
+        user_thread.join()
+
+        if task_exception:
+            raise task_exception
+
+        return task_returned_code
+    except KeyboardInterrupt:
+        gobject_mainloop.quit()
+        # We assume that if we exit with keyboard interrupt than it is not the expected
+        # behaviour and we return -1
+        return -2