Dont block UI while waiting for speech to start

src/calibre/gui2/tts/windows.py

@@ -76,7 +76,13 @@ class Client:
                     self.current_chunk_idx += 1
                     self.backend.speak(self.current_chunks[self.current_chunk_idx], is_cued=True)
             elif x.state is MediaState.failed:
-                raise x.as_exception()
+                self.clear_chunks()
+                self.callback_ignoring_errors(Event(EventType.cancel))
+                e = x.as_exception()
+                e.display_to_user = True
+                raise e
+            elif x.state is MediaState.opened:
+                self.callback_ignoring_errors(Event(EventType.begin))
         elif isinstance(x, Error):
             raise x.as_exception(check_for_no_audio_devices=True)
         else:

src/calibre/gui2/viewer/tts.py

@@ -57,9 +57,11 @@ class TTS(QObject):
     def dispatch_on_main_thread(self, func):
         try:
             func()
-        except Exception:
+        except Exception as e:
             import traceback
             traceback.print_exc()
+            if getattr(e, 'display_to_user', False):
+                error_dialog(self.parent(), _('Error in speech subsystem'), str(e), det_msg=traceback.format_exc(), show=True)
 
     @property
     def tts_client_class(self):

src/calibre/utils/windows/winspeech.py

@@ -121,8 +121,8 @@ class Error(NamedTuple):
 
     def as_exception(self, msg='', check_for_no_audio_devices=False):
         if check_for_no_audio_devices and self.hr == 0xc00d36fa:
-            raise NoAudioDevices()
-        raise SpeechError(self, msg)
+            return NoAudioDevices()
+        return SpeechError(self, msg)
 
 
 class Synthesizing(NamedTuple):
@@ -396,9 +396,7 @@ class WinSpeech:
             st = 'cued' if is_cued else ('ssml' if is_xml else 'text')
             sz = encode_to_file_object(text, shm)
             self.current_speak_cmd_id = self.send_command(f'speak {st} shm {sz} {shm.name}')
-            x = self.wait_for('speech synthesis to start', MediaStateChanged, related_to=self.current_speak_cmd_id, timeout=8)
-            if x.state is MediaState.failed:
-                raise x.as_exception()
+            self.wait_for('speech synthesis to start', Synthesizing, related_to=self.current_speak_cmd_id, timeout=8)
         return self.current_speak_cmd_id
 
     def dispatch_message(self, x):

src/pyj/read_book/read_aloud.pyj

@@ -243,6 +243,8 @@ class ReadAloud:
                 self.play()
             if data is not None:
                 pass
+        elif which is 'cancel':
+            self.state = STOPPED
 
     def send_message(self, type, **kw):
         self.view.iframe_wrapper.send_message('tts', type=type, **kw)