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)
@@ -13,9 +13,65 @@
    */
   var ExtensionCommandList = cr.ui.define('div');
 
+  /**
+   * 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.
+   * @return {boolean} Returns whether the char is valid.
+   */
+  function validChar(keyCode) {
+    return (keyCode >= 'A'.charCodeAt(0) && keyCode <= 'Z'.charCodeAt(0)) ||
+           (keyCode >= '0'.charCodeAt(0) && keyCode <= '9'.charCodeAt(0));
+  }
+
+  /**
+   * Convert a keystroke event to string form, while taking into account
+   * (ignoring) invalid extension commands.
+   * @param {Event} event The keyboard event to convert.
+   * @return {string} The keystroke as a string.
+   */
+  function keystrokeToString(event) {
+    var output = '';
+    if (event.ctrlKey)
+      output = 'Ctrl + ';
+    if (!event.ctrlKey && event.altKey)
+      output += 'Alt + ';
+    if (event.shiftKey)
+      output += 'Shift + ';
+    if (validChar(event.keyCode))
+      output += String.fromCharCode('A'.charCodeAt(0) + event.keyCode - 65);
+    return output;
+  }
+
   ExtensionCommandList.prototype = {
     __proto__: HTMLDivElement.prototype,
 
+    /**
+     * 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.
+     * @type: {keyboard event}.
+     * @private
+     */
+    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.
+     * @type: {string}.
+     * @private
+     */
+    oldValue_: '',
+
+    /**
+     * While capturing, this keeps track of which element the user asked to
+     * change.
+     * @type: {HTMLElement}.
+     * @private
+     */
+    capturingElement_: null,
+
     /** @inheritDoc */
     decorate: function() {
       this.textContent = '';
@@ -59,17 +115,137 @@
       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);
     },
+
+    /**
+     * 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 (this.capturingElement_)
+        return;  // Already capturing.
+
+      chrome.send('setShortcutHandlingSuspended', [true]);
+
+      this.oldValue_ = event.target.textContent;
+      event.target.textContent =
+          loadTimeData.getString('extensionCommandsStartTyping');
+      event.target.classList.add('capturing');
+
+      this.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 (!this.capturingElement_)
+        return;  // Not capturing.
+
+      chrome.send('setShortcutHandlingSuspended', [false]);
+
+      this.capturingElement_.classList.remove('capturing');
+      this.capturingElement_.classList.remove('contains-chars');
+      if (!this.currentKeyEvent_ || !validChar(this.currentKeyEvent_.keyCode))
+        this.capturingElement_.textContent = this.oldValue_;
+
+      if (this.oldValue_ == '')
+        this.capturingElement_.classList.remove('clearable');
+      else
+        this.capturingElement_.classList.add('clearable');
+
+      this.oldValue_ = '';
+      this.capturingElement_ = null;
+      this.currentKeyEvent_ = null;
+    },
+
+    /**
+     * The KeyDown handler.
+     * @param {Event} event The keyboard event to consider.
+     * @private
+     */
+    handleKeyDown_: function(event) {
+      if (!this.capturingElement_)
+        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 lose 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 (!this.currentKeyEvent_ || !validChar(this.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();
+      event.stopPropagation();
+
+      if (!event.ctrlKey && !event.altKey)
+        return;  // Ctrl or Alt is a must.
+
+      var keystroke = keystrokeToString(event);
+      event.target.textContent = keystroke;
+      event.target.classList.add('contains-chars');
+
+      if (validChar(event.keyCode)) {
+        this.oldValue_ = keystroke;  // Forget what the old value was.
+        chrome.send('setExtensionCommandShortcut', ['id', keystroke]);
+        this.endCapture_(event);
+      }
+
+      this.currentKeyEvent_ = event;
+    },
   };
 
   return {