Sample extensions page does not feature chrome.ttsEngine.

chrome/common/extensions/docs/examples/api/silent_tts_engine/silent_tts_engine.js

Index: chrome/common/extensions/docs/examples/api/silent_tts_engine/silent_tts_engine.js
diff --git a/chrome/common/extensions/docs/examples/api/silent_tts_engine/silent_tts_engine.js b/chrome/common/extensions/docs/examples/api/silent_tts_engine/silent_tts_engine.js
new file mode 100644
index 0000000000000000000000000000000000000000..30bc906a97a1a400661a5c3b85c83c423927fc89
--- /dev/null
+++ b/chrome/common/extensions/docs/examples/api/silent_tts_engine/silent_tts_engine.js
@@ -0,0 +1,111 @@
+var t;

[dmazzoni, 2012/05/16 05:49:58]

To be more clear, call this timeoutId or something like that

[mitchellwrosen, 2012/05/16 20:40:08]

Done.

+
+var tts_id = -1;

[dmazzoni, 2012/05/16 05:49:58]

Would prefer consistent variable naming - the Chrome style is ttsId rather than
tts_id (but consistency within the same file is most important)

[mitchellwrosen, 2012/05/16 20:40:08]

Done.

+var tts_window;
+
+var milliseconds;
+
+var curOptions;
+
+function are_new_options(options) {
+  var properties = ['voiceName', 'lang', 'gender', 'rate', 'pitch', 'volume'];
+
+  for (var i = 0; i < properties.length; ++i) {
+    if (options[properties[i]] != curOptions[properties[i]]) {
+      return true;
+    }
+  }
+
+  return false;
+}
+
+function appendText(text) {
+  tts_window.document.getElementById("text").innerHTML =

[dmazzoni, 2012/05/16 05:49:58]

Put tts_window.document in a global like tts_doc.

Alternatively make a utility function getTtsElement that calls
tts_window.document.getElementById so all you need is:

getTtsElement("text").innerHTML = ...

[mitchellwrosen, 2012/05/16 20:40:08]

Done.

+      tts_window.document.getElementById("text").innerHTML + text;

[dmazzoni, 2012/05/16 05:49:58]

Use the += operator

[mitchellwrosen, 2012/05/16 20:40:08]

Done.

+}
+
+function log_options() {
+  tts_window.document.getElementById("voiceName").innerHTML =
+      curOptions.voiceName;
+  tts_window.document.getElementById("lang").innerHTML = curOptions.lang;
+  tts_window.document.getElementById("gender").innerHTML = curOptions.gender;
+  tts_window.document.getElementById("rate").innerHTML = curOptions.rate;
+  tts_window.document.getElementById("pitch").innerHTML = curOptions.pitch;
+  tts_window.document.getElementById("volume").innerHTML = curOptions.volume;
+}
+
+function log_utterance(utterance, index, sendTtsEvent) {
+  if (index == utterance.length) {
+    sendTtsEvent({'type': 'end', 'charIndex': utterance.length});
+    return;
+  }
+
+  appendText(utterance[index]);
+
+  if (utterance[index] == ' ') {
+    sendTtsEvent({'type': 'word', 'charIndex': index});
+  }
+  else if (utterance[index] == '.' ||
+      utterance[index] == '?' ||
+      utterance[index] == '!') {
+    sendTtsEvent({'type': 'sentence', 'charIndex': index});
+  }
+
+  t = setTimeout(function(){log_utterance(utterance, ++index, sendTtsEvent)},

[dmazzoni, 2012/05/16 05:49:58]

Indent it just like any other function, like this:

t = setTimeout(function() {
  log_utterance(utterance, ++index, sendTtsEvent)
}, milliseconds);

[mitchellwrosen, 2012/05/16 20:40:08]

Done.

+      milliseconds);
+}
+
+var speakListener = function(utterance, options, sendTtsEvent) {
+  clearTimeout(t);
+
+  sendTtsEvent({'type': 'start', 'charIndex': 0});
+
+  if (tts_id == -1) {
+    // Create a new window that overlaps the bottom 40% of the current window
+    chrome.windows.getCurrent(function(cur_window) {
+      chrome.windows.create(
+          {"url": "silent_tts_engine.html",
+           "focused": false,
+           "top": Math.round(cur_window.top + 6/10 * cur_window.height),
+           "left": cur_window.left,
+           "width": cur_window.width,
+           "height": Math.round(4/10 * cur_window.height)},
+          function(new_window) {
+            tts_id = new_window.id;
+            tts_window = chrome.extension.getViews({"windowId": tts_id})[0];
+
+            curOptions = options;
+            log_options();
+
+            // Fastest timeout == 1 ms (@ options.rate = 10.0)
+            milliseconds = 10 / curOptions.rate;
+            log_utterance(utterance, 0, sendTtsEvent);
+          }
+      );
+    });
+  } else {
+    if (are_new_options(options)) {
+      curOptions = options;
+      log_options();
+
+      milliseconds = 10 / curOptions.rate;
+    }
+
+    log_utterance(utterance, 0, sendTtsEvent);
+  }
+
+};
+
+var stopListener = function() {
+  clearTimeout(t);
+};
+
+var removedListener = function(windowId, removeInfo) {
+  if (tts_id == windowId) {
+    tts_id = -1;
+  }
+}
+
+chrome.ttsEngine.onSpeak.addListener(speakListener);
+chrome.ttsEngine.onStop.addListener(stopListener);
+chrome.windows.onRemoved.addListener(removedListener);