speech: add awful hack around Python threading problem

MAV> Detected vehicle 1:1 on link 0
Using speech backend 'speechd'
Traceback (most recent call last):
  File "/usr/lib/python3.10/multiprocessing/queues.py", line 244, in _feed
    obj = _ForkingPickler.dumps(obj)
  File "/usr/lib/python3.10/multiprocessing/reduction.py", line 51, in dumps
    cls(buf, protocol).dump(obj)
  File "/usr/lib/python3.10/multiprocessing/connection.py", line 968, in reduce_connection
    df = reduction.DupFd(conn.fileno())
  File "/usr/lib/python3.10/multiprocessing/connection.py", line 170, in fileno
    self._check_closed()
  File "/usr/lib/python3.10/multiprocessing/connection.py", line 136, in _check_closed
    raise OSError("handle is closed")
OSError: handle is closed

Author: peterbarker

Diff for: MAVProxy/modules/mavproxy_speech.py

@@ -167,8 +167,9 @@ def __init__(self, mpstate):
             self.settings.set('speech_voice', '')
         except AttributeError:
             self.settings.append(('speech_voice', str, ''))
-        self.settings.set_callback(self.settings_callback)
         self.backend = SpeechBackend(self.settings)
+        self.settings_set_callback_installed = False
+        self.settings_set_callback_delay = None
 
     def settings_callback(self, setting):
         '''handle changes in settings'''
@@ -214,6 +215,21 @@ def cmd_speech(self, args):
         if args[0] == "list_voices":
             self.backend.send(SpeechCommandListVoices())
 
+    def idle_task(self):
+        if not self.settings_set_callback_installed:
+            now = time.time()
+            if self.settings_set_callback_delay is None:
+                self.settings_set_callback_delay_start = now
+            if now - self.settings_set_callback_delay_start < 1:
+                return
+            self.settings_set_callback_delay = None
+
+            try:
+                self.settings.set_callback(self.settings_callback)
+                self.settings_set_callback_installed = True
+            except Exception as ex:
+                print("Caught exception (%s)" % str(ex))
+
 def init(mpstate):
     '''initialise module'''
     return SpeechModule(mpstate)