Revive voronoi multi-threaded demo.

native_client_sdk/src/examples/demo/voronoi/example.js

Index: native_client_sdk/src/examples/demo/voronoi/example.js
===================================================================
--- native_client_sdk/src/examples/demo/voronoi/example.js	(revision 0)
+++ native_client_sdk/src/examples/demo/voronoi/example.js	(revision 0)
@@ -0,0 +1,81 @@
+// Copyright (c) 2013 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.
+
+// Add event listeners after the NaCl module has loaded.  These listeners will
+// forward messages to the NaCl module via postMessage()
+function moduleDidLoad() {

[binji, 2013/05/24 21:47:55]

we usually use attachListeners() for this. See the nacl_io example

[nfullagar1, 2013/05/28 23:11:50]

Done.

+  document.getElementById("benchmark").addEventListener("click",

[binji, 2013/05/24 21:47:55]

single quotes for strings

[nfullagar1, 2013/05/28 23:11:50]

Done.

+    function() {
+      common.naclModule.postMessage("run benchmark");
+      alert("Please wait while running benchmark.")

[binji, 2013/05/24 21:47:55]

alert() doesn't work in packaged apps.

[nfullagar1, 2013/05/28 23:11:50]

Ok, changed to update Status: while benchmarking

+    }, false);

[binji, 2013/05/24 21:47:55]

", false" shouldn't be needed. We don't need to capture events from child
elements here.

[nfullagar1, 2013/05/28 23:11:50]

Done.

+  document.getElementById("draw_points").addEventListener("click",

[binji, 2013/05/24 21:47:55]

we use camelCase for ids

[nfullagar1, 2013/05/28 23:11:50]

Done.

+    function() {
+      var checked = document.getElementById("draw_points").checked;
+      if (checked)
+        common.naclModule.postMessage("with points");
+      else
+        common.naclModule.postMessage("without points");
+    }, false);
+  document.getElementById("draw_interiors").addEventListener("click",
+    function() {
+      var checked = document.getElementById("draw_interiors").checked;
+      if (checked)
+        common.naclModule.postMessage("with interiors");
+      else
+        common.naclModule.postMessage("without interiors");
+    }, false);
+  document.getElementById("one").addEventListener("click",

[binji, 2013/05/24 21:47:55]

this could probably be made a lot more obvious by name the elements radio1,
radio2, etc. and looping over the list:

threads = [1,2,4,...];
for (var i = 0; i < threads.length; ++i) {
  // this anonymous function is necessary to capture the current value of i, or
all closures will use the last value of i.
  (function (i) {
    document.getElementById('radio'+i).addEventListener('click', ...)
  })(i);
}

[nfullagar1, 2013/05/28 23:11:50]

Done.

+    function() {
+      common.naclModule.postMessage("threads: 1");
+    }, false);
+  document.getElementById("two").addEventListener("click",
+    function() {
+      common.naclModule.postMessage("threads: 2");
+    }, false);
+  document.getElementById("four").addEventListener("click",
+    function() {
+      common.naclModule.postMessage("threads: 4");
+    }, false);
+  document.getElementById("six").addEventListener("click",
+    function() {
+      common.naclModule.postMessage("threads: 6");
+    }, false);
+  document.getElementById("eight").addEventListener("click",
+    function() {
+      common.naclModule.postMessage("threads: 8");
+    }, false);
+  document.getElementById("twelve").addEventListener("click",
+    function() {
+      common.naclModule.postMessage("threads: 12");
+    }, false);
+  document.getElementById("sixteen").addEventListener("click",
+    function() {
+      common.naclModule.postMessage("threads: 16");
+    }, false);
+  document.getElementById("twentyfour").addEventListener("click",
+    function() {
+      common.naclModule.postMessage("threads: 24");
+    }, false);
+  document.getElementById("thirtytwo").addEventListener("click",
+    function() {
+      common.naclModule.postMessage("threads: 32");
+    }, false);
+
+  document.getElementById("point_range").addEventListener("change",
+    function() {
+      var value = document.getElementById("point_range").value;
+      common.naclModule.postMessage("points: " + value);
+      document.getElementById("point_count").textContent = value + " points";
+    }, false);
+}
+
+// Handle a message coming from the NaCl module.
+// In the Voronoi example, the only message will be the benchmark result.
+function handleMessage(message_event) {
+  var x = Math.round(message_event.data * 1000) / 1000;

[binji, 2013/05/24 21:47:55]

You can just use parseFloat(message_event.data) to convert from a string, and
rely on toFixed to round it.

[nfullagar1, 2013/05/28 23:11:50]

This arrives as a float, and we're rounding to 3 digits.  (toFixed doesn't
round.)

[binji, 2013/05/28 23:37:50]

Seems to from my tests in the Chrome console:
(3.0045).toFixed(3)
"3.005"
(3.0044).toFixed(3)
"3.004"

[nfullagar1, 2013/05/29 01:19:53]

I should have said toFixed doesn't round 'as expected.' :) The Stackoverflow
articles indicate toFixed is inconsistent regarding rounding across platforms,
and the oft suggested workaround is to use var roundedNum = (Math.round( num *
1000 ) / 1000).toFixed(3); (substitute 1000 and 3 as needed.)
Try:
(3.1245).toFixed(3)
"3.124"
(Math.round(3.1245 * 1000) / 1000).toFixed(3)
"3.125"
x=3.442500000000000001
x.toFixed(3)
"3.442"
(Math.round(x * 1000) / 1000).toFixed(3)
"3.443"

+  document.getElementById("result").textContent =
+    "Result: " + x.toFixed(3) + " seconds";
+}
+