Config UI for Extension Commands (part 1).

chrome/browser/resources/extensions/extension_command_list.js

Index: chrome/browser/resources/extensions/extension_command_list.js
===================================================================
--- chrome/browser/resources/extensions/extension_command_list.js	(revision 140271)
+++ chrome/browser/resources/extensions/extension_command_list.js	(working copy)
@@ -13,6 +13,25 @@
    */
   var ExtensionCommandList = cr.ui.define('div');
 
+  /**
+   * While capturing, this records the current (last) keyboard event generated
+   * by the user. Will be |null| after capture and during capture when no
+   * keyboard event has been generated.
+   */
+  var currentKeyEvent = null;
+
+  /**
+   * While capturing, this keeps track of the previous selection so we can
+   * revert back to if no valid assignment is made during capture.
+   */
+  var oldValue = '';
+
+  /**
+   * While capturing, this keeps track of which element the user asked to
+   * change.
+   */
+  var capturingElement = null;
+
   ExtensionCommandList.prototype = {
     __proto__: HTMLDivElement.prototype,
 
@@ -59,17 +78,167 @@
       var description = node.querySelector('.command-description');
       description.textContent = command.description;
 
-      var shortcut = node.querySelector('.command-shortcut');
+      var command_shortcut = node.querySelector('.command-shortcut');
+      command_shortcut.addEventListener('mouseup',
+                                        this.startCapture_.bind(this));
+      command_shortcut.addEventListener('blur', this.endCapture_.bind(this));
+      command_shortcut.addEventListener('keydown',
+                                        this.handleKeyDown_.bind(this));
+      command_shortcut.addEventListener('keyup', this.handleKeyUp_.bind(this));
+
       if (!command.active) {
-        shortcut.textContent =
+        command_shortcut.textContent =
             loadTimeData.getString('extensionCommandsInactive');
-        shortcut.classList.add('inactive-keybinding');
+        command_shortcut.classList.add('inactive-keybinding');
       } else {
-        shortcut.textContent = command.keybinding;
+        command_shortcut.textContent = command.keybinding;
       }
 
       this.appendChild(node);
     },
+
+    /**
+     * Convert a keystroke event to string form, while taking into account
+     * (ignoring) invalid extension commands.
+     * @param {Event} event The keyboard event to convert.
+     * @private
+     */
+    keystrokeToString_: function(event) {
+      var output = event.ctrlKey ? 'Ctrl + ' : '';
+      if (!event.ctrlKey)
+        output += event.altKey ? 'Alt + ' : '';
+      output += event.shiftKey ? 'Shift + ' : '';

[Evan Stade, 2012/06/05 00:20:37]

imo, it's easier to read

if (event.fooKey)
  output += 'Foo + ';

+      if (this.validChar_(event.keyCode))
+        output += String.fromCharCode('A'.charCodeAt(0) + event.keyCode - 65);
+      return output;
+    },
+
+    /**
+     * Returns whether the passed in |keyCode| is a valid extension command
+     * char or not. This is restricted to A-Z and 0-9 (ignoring modifiers) at
+     * the moment.
+     * @param {int} keyCode The keycode to consider.
+     * @private
+     */
+    validChar_: function(keyCode) {
+      return (keyCode >= 'A'.charCodeAt(0) && keyCode <= 'Z'.charCodeAt(0)) ||
+             (keyCode >= '0'.charCodeAt(0) && keyCode <= '9'.charCodeAt(0));
+    },
+
+    /**
+     * Starts keystroke capture to determine which key to use for a particular
+     * extension command.
+     * @param {Event} event The keyboard event to consider.
+     * @private
+     */
+    startCapture_: function(event) {
+      if (capturingElement !== null)
+        return;  // Already capturing.
+
+      chrome.send('setShortcutHandlingSuspended', [true]);
+
+      oldValue = event.target.textContent;
+      event.target.textContent =
+          loadTimeData.getString('extensionCommandsStartTyping');
+      event.target.classList.add('capturing');
+
+      capturingElement = event.target;
+    },
+
+    /**
+     * Ends keystroke capture and either restores the old value or (if valid
+     * value) sets the new value as active..
+     * @param {Event} event The keyboard event to consider.
+     * @private
+     */
+    endCapture_: function(event) {
+      if (capturingElement === null)
+        return;  // Not capturing.
+
+      chrome.send('setShortcutHandlingSuspended', [false]);
+
+      capturingElement.classList.remove('capturing');
+      capturingElement.classList.remove('contains-chars');
+      if (currentKeyEvent == null ||
+          !this.validChar_(currentKeyEvent.keyCode))
+        capturingElement.textContent = oldValue;
+
+      if (oldValue == '')
+        capturingElement.classList.remove('clearable');
+      else
+        capturingElement.classList.add('clearable');
+
+      oldValue = '';
+      capturingElement = null;
+      currentKeyEvent = null;
+    },
+
+    /**
+     * The KeyDown handler.
+     * @param {Event} event The keyboard event to consider.
+     * @private
+     */
+    handleKeyDown_: function(event) {
+      if (capturingElement === null)
+        this.startCapture_(event);
+
+      this.handleKey_(event);
+    },
+
+    /**
+     * The KeyUp handler.
+     * @param {Event} event The keyboard event to consider.
+     * @private
+     */
+    handleKeyUp_: function(event) {
+      // We want to make it easy to change from Ctrl+Shift+ to just Ctrl+ by
+      // releasing Shift, but we also don't want it to be easy to loose for
+      // example Ctrl+Shift+F to Ctrl+ just because you didn't release Ctrl
+      // as fast as the other two keys. Therefore, we process KeyUp until you
+      // have a valid combination and then stop processing it (meaning that once
+      // you have a valid combination, we won't change it until the next
+      // KeyDown message arrives).
+      if (currentKeyEvent === null ||
+          !this.validChar_(currentKeyEvent.keyCode)) {
+        if (!event.ctrlKey && !event.altKey) {
+          // If neither Ctrl nor Alt is pressed then it is not a valid shortcut.
+          // That means we're back at the starting point so we should restart
+          // capture.
+          this.endCapture_(event);
+          this.startCapture_(event);
+        } else {
+          this.handleKey_(event);
+        }
+      }
+    },
+
+    /**
+     * A general key handler (used for both KeyDown and KeyUp).
+     * @param {Event} event The keyboard event to consider.
+     * @private
+     */
+    handleKey_: function(event) {
+      // While capturing, we prevent all events from bubbling, to prevent
+      // shortcuts lacking the right modifier (F3 for example) from activating
+      // and ending capture prematurely.
+      event.preventDefault();
+
+      if (!event.ctrlKey && !event.altKey)
+        return true;  // Ctrl or Alt is a must.
+
+      var keystroke = this.keystrokeToString_(event);
+      event.target.textContent = keystroke;
+      event.target.classList.add('contains-chars');
+      currentKeyEvent = event;
+
+      if (this.validChar_(event.keyCode)) {
+        oldValue = keystroke;  // Forget what the old value was.
+        chrome.send('setExtensionCommandShortcut', ['id', keystroke]);
+        this.endCapture_(event);
+      }
+
+      return false;
+    },
   };
 
   return {