From 3f9febc9ec371ef1b090ebe2f5c0c7185c115bd9 Mon Sep 17 00:00:00 2001
From: Kovid Goyal <kovid@kovidgoyal.net>
Date: Mon, 26 Aug 2024 13:08:43 +0530
Subject: [PATCH] More work on TTS backends

---
 src/calibre/gui2/tts2/qt.py    |  8 ++++++++
 src/calibre/gui2/tts2/types.py | 18 +++++++++++++-----
 2 files changed, 21 insertions(+), 5 deletions(-)

diff --git a/src/calibre/gui2/tts2/qt.py b/src/calibre/gui2/tts2/qt.py
index 6f55a0e91d..fe50e317e6 100644
--- a/src/calibre/gui2/tts2/qt.py
+++ b/src/calibre/gui2/tts2/qt.py
@@ -85,6 +85,14 @@ class QtTTSBackend(QObject):
         self.tts.sayingWord.connect(self._saying_word)
         self.tts.stateChanged.connect(self.state_changed.emit)
 
+    def change_rate(self, steps: int = 1) -> bool:
+        current = self.tts.rate()
+        new_rate = max(-1, min(current + 0.2 * steps, 1))
+        if current == new_rate:
+            return False
+        self.tts.setRate(new_rate)
+        return True
+
     def shutdown(self) -> None:
         self.tts.stop(QTextToSpeech.BoundaryHint.Immediate)
 
diff --git a/src/calibre/gui2/tts2/types.py b/src/calibre/gui2/tts2/types.py
index 904a77b41a..6e4dac45cd 100644
--- a/src/calibre/gui2/tts2/types.py
+++ b/src/calibre/gui2/tts2/types.py
@@ -1,6 +1,7 @@
 #!/usr/bin/env python
 # License: GPLv3 Copyright: 2024, Kovid Goyal <kovid at kovidgoyal.net>
 
+import os
 from enum import Enum, auto
 from functools import lru_cache
 from typing import Literal, NamedTuple
@@ -23,7 +24,6 @@ class EngineMetadata(NamedTuple):
     allows_choosing_audio_device: bool = True
     can_synthesize_audio_data: bool = True
     has_multiple_output_modules: bool = False
-    can_change_rate: bool = True
     can_change_pitch: bool = True
     can_change_volume: bool = True
 
@@ -92,7 +92,12 @@ def available_engines() -> dict[str, EngineMetadata]:
         elif x == 'flite':
             ans[x] = qt_engine_metadata(x, True)
         elif x == 'speechd':
-            ans[x] = EngineMetadata(x, TrackingCapability.WordByWord, allows_choosing_audio_device=False, has_multiple_output_modules=True)
+            continue
+    if islinux:
+        from speechd.paths import SPD_SPAWN_CMD
+        cmd = os.getenv("SPEECHD_CMD", SPD_SPAWN_CMD)
+        if cmd and os.access(cmd, os.X_OK) and os.path.isfile(cmd):
+            ans['speechd'] = EngineMetadata('speechd', TrackingCapability.WordByWord, allows_choosing_audio_device=False, has_multiple_output_modules=True)
     return ans
 
 
@@ -101,11 +106,14 @@ def create_tts_backend(engine_name: str = '', settings: EngineSpecificSettings =
         engine_name = 'speechd'
     if engine_name not in available_engines():
         engine_name = ''
+
     if engine_name == 'speechd':
         from calibre.gui2.tts2.speechd import SpeechdTTSBackend
-        return SpeechdTTSBackend(engine_name, settings, parent)
-    from calibre.gui2.tts2.qt import QtTTSBackend
-    return QtTTSBackend(engine_name, settings, parent)
+        ans = SpeechdTTSBackend(engine_name, settings, parent)
+    else:
+        from calibre.gui2.tts2.qt import QtTTSBackend
+        ans = QtTTSBackend(engine_name, settings, parent)
+    return ans
 
 
 def develop(engine_name=''):