E-book viewer: When using Read aloud do not automatically lookup the highlighted word until read aloud is paused or stopped. Fixes #1959207 [E-book viewer's "read the text aloud" function conflicts with dictionary lookup](https://bugs.launchpad.net/calibre/+bug/1959207)

src/calibre/gui2/viewer/lookup.py

@@ -238,6 +238,12 @@ class View(QWebEngineView):
         self.inspect_element.emit()
 
 
+def set_sync_override(allowed):
+    li = getattr(set_sync_override, 'instance', None)
+    if li is not None:
+        li.set_sync_override(allowed)
+
+
 class Lookup(QWidget):
 
     def __init__(self, parent):
@@ -275,6 +281,7 @@ class Lookup(QWidget):
         l.addLayout(h)
         h.addWidget(b), h.addWidget(rb)
         self.auto_update_query = a = QCheckBox(_('Update on selection change'), self)
+        self.disallow_auto_update = False
         a.setToolTip(textwrap.fill(
             _('Automatically update the displayed result when selected text in the book changes. With this disabled'
               ' the lookup is changed only when clicking the Refresh button.')))
@@ -282,6 +289,12 @@ class Lookup(QWidget):
         a.stateChanged.connect(self.auto_update_state_changed)
         l.addWidget(a)
         self.update_refresh_button_status()
+        set_sync_override.instance = self
+
+    def set_sync_override(self, allowed):
+        self.disallow_auto_update = not allowed
+        if self.auto_update_query.isChecked() and allowed:
+            self.update_query()
 
     def auto_update_state_changed(self, state):
         vprefs['auto_update_lookup'] = self.auto_update_query.isChecked()
@@ -370,7 +383,7 @@ class Lookup(QWidget):
     def selected_text_changed(self, text, annot_id):
         already_has_text = bool(self.current_query)
         self.selected_text = text or ''
-        if self.auto_update_query.isChecked() or not already_has_text:
+        if not self.disallow_auto_update and (self.auto_update_query.isChecked() or not already_has_text):
             self.debounce_timer.start()
         self.update_refresh_button_status()
 

src/calibre/gui2/viewer/tts.py

@@ -1,13 +1,18 @@
 #!/usr/bin/env python
 # License: GPL v3 Copyright: 2020, Kovid Goyal <kovid at kovidgoyal.net>
 
-from qt.core import QDialogButtonBox, QObject, QVBoxLayout, pyqtSignal, QDialog
+from qt.core import QDialog, QDialogButtonBox, QObject, QVBoxLayout, pyqtSignal
 
 from calibre.gui2 import error_dialog
 from calibre.gui2.viewer.config import get_pref_group, vprefs
 from calibre.gui2.widgets2 import Dialog
 
 
+def set_sync_override(allowed):
+    from calibre.gui2.viewer.lookup import set_sync_override
+    set_sync_override(allowed)
+
+
 class Config(Dialog):
 
     def __init__(self, tts_client, ui_settings, backend_settings, parent):
@@ -89,15 +94,19 @@ class TTS(QObject):
             return error_dialog(self.parent(), _('Text-to-Speech unavailable'), str(err), show=True)
 
     def play(self, data):
+        set_sync_override(False)
         self.tts_client.speak_marked_text(data['marked_text'], self.callback)
 
     def pause(self, data):
+        set_sync_override(True)
         self.tts_client.pause()
 
     def resume(self, data):
+        set_sync_override(False)
         self.tts_client.resume()
 
     def resume_after_configure(self, data):
+        set_sync_override(False)
         self.tts_client.resume_after_configure()
 
     def callback(self, event):
@@ -107,6 +116,7 @@ class TTS(QObject):
         self.event_received.emit(event.type.name, data)
 
     def stop(self, data):
+        set_sync_override(True)
         self.tts_client.stop()
 
     @property