Refactored TTS extension code so that the platform-specific TTS...

chrome/browser/extensions/extension_tts_api_mac.mm

 // Copyright (c) 2010 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "extension_tts_api.h"
 
 #include <string>
 
+#include "base/singleton.h"
 #include "base/values.h"
 #include "chrome/browser/extensions/extension_function.h"
 
 #import <Cocoa/Cocoa.h>
 
 namespace util = extension_tts_api_util;
 
-static NSSpeechSynthesizer* speech_synthesizer_;
+class ExtensionTtsPlatformImplMac : public ExtensionTtsPlatformImpl {
+ public:
+  virtual bool Speak(
+      const std::string& utterance,
+      const std::string& language,
+      const std::string& gender,
+      double rate,
+      double pitch,
+      double volume);
 
-void InitializeSpeechSynthesizer() {
-  if (!speech_synthesizer_)
-    speech_synthesizer_ = [[NSSpeechSynthesizer alloc] init];
+  virtual bool StopSpeaking();
+
+  virtual bool IsSpeaking();
+
+  // Get the single instance of this class.
+  static ExtensionTtsPlatformImplMac* GetInstance();
+
+ private:
+  ExtensionTtsPlatformImplMac();
+  virtual ~ExtensionTtsPlatformImplMac() {}
+
+  NSSpeechSynthesizer* speech_synthesizer_;
+
+  friend struct DefaultSingletonTraits<ExtensionTtsPlatformImplMac>;
+
+  DISALLOW_COPY_AND_ASSIGN(ExtensionTtsPlatformImplMac);
+};
+
+// static
+ExtensionTtsPlatformImpl* ExtensionTtsPlatformImpl::GetInstance() {
+  return ExtensionTtsPlatformImplMac::GetInstance();
 }
 
-bool ExtensionTtsSpeakFunction::RunImpl() {
-  InitializeSpeechSynthesizer();
-  std::string utterance;
-  EXTENSION_FUNCTION_VALIDATE(args_->GetString(0, &utterance));
-  DictionaryValue* speak_options = NULL;
+bool ExtensionTtsPlatformImplMac::Speak(
+    const std::string& utterance,
+    const std::string& language,
+    const std::string& gender,
+    double rate,
+    double pitch,
+    double volume) {
+  // NSSpeechSynthesizer equivalents for kGenderKey and kLanguageNameKey do
+  // not exist and thus are not supported.
 
-  // Parse speech properties.
-  if (args_->GetDictionary(1, &speak_options)) {
-    std::string str_value;
-    double real_value;
-    // NSSpeechSynthesizer equivalents for kGenderKey and kLanguageNameKey do
-    // not exist and thus are not supported.
-    if (util::ReadNumberByKey(speak_options, util::kRateKey, &real_value)) {
-      // The TTS api defines rate via words per minute.
-      [speech_synthesizer_
-          setObject:[NSNumber numberWithInt:real_value*400]
-          forProperty:NSSpeechRateProperty error:nil];
-    }
-    if (util::ReadNumberByKey(speak_options, util::kPitchKey, &real_value)) {
-      // The TTS api allows an approximate range of 30 to 65 for speech pitch.
-      [speech_synthesizer_
-          setObject: [NSNumber numberWithInt:(real_value*35 + 30)]
-          forProperty:NSSpeechPitchBaseProperty error:nil];
-    }
-    if (util::ReadNumberByKey(speak_options, util::kVolumeKey, &real_value)) {
-      // The TTS api allows a range of 0.0 to 1.0 for speech volume.
-      [speech_synthesizer_
-          setObject: [NSNumber numberWithFloat:real_value]
-          forProperty:NSSpeechVolumeProperty error:nil];
-    }
+  if (rate >= 0.0) {
+    // The TTS api defines rate via words per minute.
+    [speech_synthesizer_
+        setObject:[NSNumber numberWithInt:rate * 400]
+        forProperty:NSSpeechRateProperty error:nil];
   }
 
-  return
-      [speech_synthesizer_ startSpeakingString:
-           [NSString stringWithUTF8String: utterance.c_str()]];
+  if (pitch >= 0.0) {
+    // The TTS api allows an approximate range of 30 to 65 for speech pitch.
+    [speech_synthesizer_
+        setObject: [NSNumber numberWithInt:(pitch * 35 + 30)]
+        forProperty:NSSpeechPitchBaseProperty error:nil];
+  }
+
+  if (volume >= 0.0) {
+    [speech_synthesizer_
+        setObject: [NSNumber numberWithFloat:volume]
+        forProperty:NSSpeechVolumeProperty error:nil];
+  }
+
+  return [speech_synthesizer_ startSpeakingString:
+             [NSString stringWithUTF8String: utterance.c_str()]];
 }
 
-bool ExtensionTtsStopSpeakingFunction::RunImpl() {
-    InitializeSpeechSynthesizer();
+bool ExtensionTtsPlatformImplMac::StopSpeaking() {
   [speech_synthesizer_ stopSpeaking];
   return true;
 }
 
-bool ExtensionTtsIsSpeakingFunction::RunImpl() {
-    InitializeSpeechSynthesizer();
+bool ExtensionTtsPlatformImplMac::IsSpeaking() {
   return [speech_synthesizer_ isSpeaking];
 }
+
+ExtensionTtsPlatformImplMac::ExtensionTtsPlatformImplMac() {
+  speech_synthesizer_ = [[NSSpeechSynthesizer alloc] init];
+}
+
+// static
+ExtensionTtsPlatformImplMac* ExtensionTtsPlatformImplMac::GetInstance() {
+  return Singleton<ExtensionTtsPlatformImplMac>::get();
+}