Implement ChromeVox Next menus.

chrome/browser/resources/chromeos/chromevox/cvox2/background/panel_menu.js

+// Copyright 2016 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.
+
+/**
+ * @fileoverview A drop-down menu in the ChromeVox panel.
+ */
+
+goog.provide('PanelMenu');
+
+goog.require('PanelMenuItem');
+
+/**
+ * @param {string} menuTitle The title of the menu.
+ * @constructor
+ */
+PanelMenu = function(menuTitle) {
+  // The item in the menu bar containing the menu's title.
+  this.menuBarItemElement = document.createElement('div');
+  this.menuBarItemElement.className = 'menu-bar-item';
+  this.menuBarItemElement.setAttribute('role', 'menu');
+  this.menuBarItemElement.textContent = menuTitle;
+
+  // The container for the menu. This part is fixed and scrolls its
+  // contents if necessary.
+  this.menuContainerElement = document.createElement('div');
+  this.menuContainerElement.className = 'menu-container';
+  this.menuContainerElement.style.visibility = 'hidden';
+
+  // The menu itself. It contains all of the items, and it scrolls within
+  // its container.
+  this.menuElement = document.createElement('table');
+  this.menuElement.className = 'menu';
+  this.menuElement.setAttribute('role', 'menu');
+  this.menuElement.setAttribute('aria-label', menuTitle);
+  this.menuContainerElement.appendChild(this.menuElement);
+
+  /**
+   * The items in the menu.
+   * @type Array<PanelMenuItem>

[David Tseng, 2016/01/12 20:10:57]

Invalid js doc? @type {!A...}

[dmazzoni, 2016/01/13 23:26:40]

Done.

+   * @private
+   */
+  this.items_ = [];
+
+  /**
+    * The return value from window.setTimeout for a function to update the
+    * scroll bars after an item has been added to a menu. Used so that we
+    * don't re-layout too many times.
+    * @type {?number}
+    * @private
+    */
+  this.updateScrollbarsTimeout_ = null;
+
+  /**
+   * The current active menu item index, or -1 if none.
+   * @type {number}
+   * @private
+   */
+  this.activeIndex_ = -1;
+};
+
+PanelMenu.prototype = {
+  /**
+   * @param {string} menuItemTitle The title of the menu item.
+   * @param {string} menuItemShortcut The keystrokes to select this item.
+   * @param {Function} callback The function to call if this item is selected.
+   * @return {!PanelMenuItem} The menu item just created.
+   */
+  addMenuItem: function(menuItemTitle, menuItemShortcut, callback) {
+    var menuItem = new PanelMenuItem(menuItemTitle, menuItemShortcut, callback);
+    this.items_.push(menuItem);
+    this.menuElement.appendChild(menuItem.element);
+
+    // Sync the active index with focus.
+    menuItem.element.addEventListener('focus', (function(index, event) {
+      this.activeIndex_ = index;
+    }).bind(this, this.items_.length - 1), false);
+
+    // Update the container height, adding a scroll bar if necessary - but
+    // to avoid excessive layout, schedule this once per batch of adding
+    // menu items rather than after each add.
+    if (!this.updateScrollbarsTimeout_) {
+      this.updateScrollbarsTimeout_ = window.setTimeout((function() {
+        var menuBounds = this.menuElement.getBoundingClientRect();
+        var maxHeight = window.innerHeight - menuBounds.top;
+        this.menuContainerElement.style.maxHeight = maxHeight + 'px';
+        this.updateScrollbarsTimeout_ = null;
+      }).bind(this), 0);
+    }
+
+    return menuItem;
+  },
+
+  /**
+   * Activate this menu, which means showing it and positioning it on the
+   * screen underneath its title in the menu bar.
+   */
+  activate: function() {
+    this.menuContainerElement.style.visibility = 'visible';
+    this.menuContainerElement.style.opacity = 1;
+    this.menuBarItemElement.classList.add('active');
+    var barBounds =
+        this.menuBarItemElement.parentElement.getBoundingClientRect();
+    var titleBounds = this.menuBarItemElement.getBoundingClientRect();
+    var menuBounds = this.menuElement.getBoundingClientRect();
+
+    this.menuElement.style.minWidth = titleBounds.width + 'px';
+    this.menuContainerElement.style.minWidth = titleBounds.width + 'px';
+    if (titleBounds.left + menuBounds.width < barBounds.width) {
+      this.menuContainerElement.style.left = titleBounds.left + 'px';
+    } else {
+      this.menuContainerElement.style.left =
+          (titleBounds.right - menuBounds.width) + 'px';
+    }
+
+    // Make the first item active.
+    this.activateItem(0);
+  },
+
+  /**
+   * Hide this menu. Make it invisible first to minimize spurious
+   * accessibility events before the next menu activates.
+   */
+  deactivate: function() {
+    this.menuContainerElement.style.opacity = 0.001;
+    this.menuBarItemElement.classList.remove('active');
+    this.activeIndex_ = -1;
+
+    window.setTimeout((function() {
+      this.menuContainerElement.style.visibility = 'hidden';
+    }).bind(this), 0);
+  },
+
+  /**
+   * Make a specific menu item index active.
+   * @param {number} itemIndex The index of the menu item.
+   */
+  activateItem: function(itemIndex) {
+    this.activeIndex_ = itemIndex;
+    if (this.activeIndex_ >= 0 && this.activeIndex_ < this.items_.length) {
+      this.items_[this.activeIndex_].element.focus();
+    }

[David Tseng, 2016/01/12 20:10:57]

nit: remove braces

[dmazzoni, 2016/01/13 23:26:40]

Done.

+  },
+
+  /**
+   * Advanced the active menu item index by a given number.
+   * @param {number} delta The number to add to the active menu item index.
+   */
+  advanceItemBy: function(delta) {
+    if (this.activeIndex_ >= 0) {
+      this.activeIndex_ += delta;
+      this.activeIndex_ =
+          (this.activeIndex_ + this.items_.length) % this.items_.length;
+    } else {
+      if (delta >= 0)
+        this.activeIndex_ = 0;
+      else
+        this.activeIndex_ = this.menus_.length - 1;
+    }
+
+    this.items_[this.activeIndex_].element.focus();
+  },
+
+  /**
+   * Get the callback for the active menu item.
+   * @return {Function} The callback.
+   */
+  getCallbackForCurrentItem: function() {
+    if (this.activeIndex_ >= 0 && this.activeIndex_ < this.items_.length) {
+      return this.items_[this.activeIndex_].callback;
+    }
+    return null;
+  },
+
+  /**
+   * Get the callback for a menu item given its DOM element.
+   * @param {Element} element The DOM element.
+   * @return {Function} The callback.
+   */
+  getCallbackForElement: function(element) {
+    for (var i = 0; i < this.items_.length; i++) {

[David Tseng, 2016/01/12 20:10:57]

Can use: this.items_.find

[dmazzoni, 2016/01/13 23:26:40]

Not any cleaner in this case because it returns the item, we still need to
extract the callback from that.

+      if (element == this.items_[i].element)
+        return this.items_[i].callback;
+    }
+    return null;
+  }
+};