Print Preview Print Destination Search Widget

chrome/browser/resources/print_preview/search/destination_list.js

+// Copyright (c) 2012 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.
+
+cr.define('print_preview', function() {
+  'use strict';
+
+  /**
+   * Component that displays a list of destinations with a heading, action link,
+   * and "Show All..." button. An event is dispatched when the action link is
+   * activated.
+   * @param {!cr.EventTarget} eventTarget Event target to pass to destination
+   *     items for dispatching SELECT events.
+   * @param {string} title Title of the destination list.
+   * @param {number=} opt_maxSize Maximum size of the list. If not specified,
+   *     defaults to no max.
+   * @param {string=} opt_actionLinkLabel Optional label of the action link. If
+   *     no label is provided, the action link will not be shown.
+   * @constructor
+   * @extends {print_preview.Component}
+   */
+  function DestinationList(
+      eventTarget, title, opt_maxSize, opt_actionLinkLabel) {
+    print_preview.Component.call(this);
+
+    /**
+     * Event target to pass to destination items for dispatching SELECT events.
+     * @type {!cr.EventTarget}
+     * @private
+     */
+    this.eventTarget_ = eventTarget;
+
+    /**
+     * Title of the destination list.
+     * @type {string}
+     * @private
+     */
+    this.title_ = title;
+
+    /**
+     * Maximum size of the destination list.
+     * @type {number}
+     * @private
+     */
+    this.maxSize_ = opt_maxSize || 0;
+    assert(this.maxSize_ <= DestinationList.SHORT_LIST_SIZE_,
+           'Max size must be less than or equal to ' +
+               DestinationList.SHORT_LIST_SIZE_);
+
+    /**
+     * Label of the action link.
+     * @type {?string}
+     * @private
+     */
+    this.actionLinkLabel_ = opt_actionLinkLabel || null;
+
+    /**
+     * Backing store for the destination list.
+     * @type {!Array.<print_preview.Destination>}
+     * @private
+     */
+    this.destinations_ = [];
+
+    /**
+     * Current query used for filtering.
+     * @type {?string}
+     * @private
+     */
+    this.query_ = null;
+
+    /**
+     * Whether the destination list is fully expanded.
+     * @type {boolean}
+     * @private
+     */
+    this.isShowAll_ = false;
+
+    /**
+     * Message to show when no destinations are available.
+     * @type {HTMLElement}
+     * @private
+     */
+    this.noDestinationsMessageEl_ = null;

[Dan Beam, 2012/05/29 23:36:10]

?HTMLElement

[Robert Toscano, 2012/05/30 21:08:00]

'?' is extraneous.

+
+    /**
+     * Footer of the list.
+     * @type {HTMLElement}
+     * @private
+     */
+    this.footerEl_ = null;
+
+    /**
+     * Container for the destination list items.
+     * @type {HTMLElement}
+     * @private
+     */
+    this.destinationListItemContainer_ = null;
+  };
+
+  /**
+   * Enumeration of event types dispatched by the destination list.
+   * @enum {string}
+   */
+  DestinationList.EventType = {
+    // Dispatched when the action linked is activated.
+    ACTION_LINK_ACTIVATED: 'print_preview.DestinationList.ACTION_LINK_ACTIVATED'
+  };
+
+  /**
+   * Classes used by the destination list.
+   * @enum {string}
+   * @private
+   */
+  DestinationList.Classes_ = {
+    ACTION_LINK: 'destination-list-action-link',
+    FOOTER: 'destination-list-footer',
+    NO_PRINTERS_MESSAGE: 'destination-list-no-destinations-message',
+    PRINTER_ITEM_CONTAINER: 'destination-list-destination-list-item-container',
+    SHOW_ALL_BUTTON: 'destination-list-show-all-button',
+    TITLE: 'destination-list-title',
+    TOTAL: 'destination-list-total'
+  };
+
+  /**
+   * Maximum number of destinations before showing the "Show All..." button.
+   * @type {number}
+   * @const
+   * @private
+   */
+  DestinationList.SHORT_LIST_SIZE_ = 5;
+
+  DestinationList.prototype = {
+    __proto__: print_preview.Component.prototype,
+
+    /** @param {boolean} isShowAll Whether the show-all button is activated. */
+    setIsShowAll: function(isShowAll) {
+      this.isShowAll_ = isShowAll;
+      this.renderDestinations_();
+    },
+
+    /** @override */
+    createDom: function() {
+      this.setElementInternal(this.cloneTemplateInternal(
+          'destination-list-template'));
+
+      var titleEl = this.getElement().getElementsByClassName(
+          DestinationList.Classes_.TITLE)[0];
+      titleEl.textContent = this.title_;
+
+      var actionLinkEl = this.getElement().getElementsByClassName(
+            DestinationList.Classes_.ACTION_LINK)[0];
+      if (this.actionLinkLabel_) {
+        actionLinkEl.textContent = this.actionLinkLabel_;
+      } else {
+        setIsVisible(actionLinkEl, false);
+      }
+
+      this.noDestinationsMessageEl_ = this.getElement().getElementsByClassName(
+          DestinationList.Classes_.NO_PRINTERS_MESSAGE)[0];
+      this.footerEl_ = this.getElement().getElementsByClassName(
+          DestinationList.Classes_.FOOTER)[0];
+      this.destinationListItemContainer_ =
+          this.getElement().getElementsByClassName(
+              DestinationList.Classes_.PRINTER_ITEM_CONTAINER)[0];
+    },
+
+    /** @override */
+    enterDocument: function() {
+      print_preview.Component.prototype.enterDocument.call(this);
+      var actionLinkEl = this.getElement().getElementsByClassName(
+          DestinationList.Classes_.ACTION_LINK)[0];
+      var showAllButton = this.getElement().getElementsByClassName(
+          DestinationList.Classes_.SHOW_ALL_BUTTON)[0];
+      this.tracker.add(
+          actionLinkEl, 'click', this.onActionLinkClick_.bind(this));
+      this.tracker.add(
+          showAllButton, 'click', this.setIsShowAll.bind(this, true));
+    },
+
+    /** @override */
+    exitDocument: function() {
+      print_preview.Component.prototype.exitDocument.call(this);
+      this.noDestinationsMessageEl_ = null;

[Dan Beam, 2012/05/29 23:36:10]

is there a reason this nulling is required?

[Robert Toscano, 2012/05/30 21:08:00]

So this object can release its reference to the DOM element and so that the DOM
element can get garbage collected.

[Dan Beam, 2012/05/31 00:17:58]

If the ref count hits 0 it should do this automagically anyways, you shouldn't
need to do this yourself. The only reason (AFAIK) that you see this done in some
code / libraries is that JScript 5.6-5.8 had bad garbage collectors. If I'm
misunderstanding (like if this object is re-used or something), ignore, just an
observation that we're trying to do pseudo-memory management in a GC'd
language...

+      this.footerEl_ = null;
+      this.destinationListItemContainer_ = null;
+    },
+
+    /**
+     * Updates the destinations to render in the destination list.
+     * @param {!Array.<print_preview.Destination>} destinations Destinations to
+     *     render.
+     */
+    updateDestinations: function(destinations) {
+      this.destinations_ = destinations;
+      this.renderDestinations_();
+    },
+
+    /**
+     * Filters the destination list with the given query.
+     * @param {?string} query Query to filter the list with.
+     */
+    filter: function(query) {
+      this.query_ = query;
+      this.renderDestinations_();
+    },
+
+    /**
+     * @param {string} text Text to set the action link to.
+     * @protected
+     */
+    setActionLinkTextInternal: function(text) {
+      this.actionLinkLabel_ = text;
+      var actionLinkEl = this.getElement().getElementsByClassName(
+            DestinationList.Classes_.ACTION_LINK)[0];
+      actionLinkEl.textContent = this.actionLinkLabel_;
+    },
+
+    /**
+     * Renders all destinations in the list that match the current query. For
+     * each render, all old destination items are first removed.
+     * @private
+     */
+    renderDestinations_: function() {
+      this.removeChildren();
+
+      var filteredDests = [];
+      this.destinations_.forEach(function(destination) {
+        if (!this.query_ || destination.matches(this.query_)) {
+          filteredDests.push(destination);
+        }
+      }, this);
+
+      // TODO(rltoscano): Sort filtered list?
+
+      if (filteredDests.length == 0) {
+        this.renderEmptyList_();
+      } else if (this.maxSize_) {
+        this.renderListWithMaxSize_(filteredDests);
+      } else {
+        this.renderListWithNoMaxSize_(filteredDests);
+      }
+    },
+
+    /**
+     * Renders a "No destinations found" element.
+     * @private
+     */
+    renderEmptyList_: function() {
+      setIsVisible(this.noDestinationsMessageEl_, true);
+      setIsVisible(this.footerEl_, false);
+    },
+
+    /**
+     * Renders the list of destinations up to the maximum size.
+     * @param {!Array.<print_preview.Destination>} filteredDests Filtered list
+     *     of print destinations to render.
+     * @private
+     */
+    renderListWithMaxSize_: function(filteredDests) {
+      setIsVisible(this.noDestinationsMessageEl_, false);
+      setIsVisible(this.footerEl_, false);
+      for (var dest, i = 0;
+           i < this.maxSize_ && (dest = filteredDests[i]);
+           i++) {
+        var destListItem = new print_preview.DestinationListItem(
+            this.eventTarget_, dest);
+        this.addChild(destListItem);
+        destListItem.render(this.destinationListItemContainer_);
+      }
+    },
+
+    /**
+     * Renders all destinations in the given list.
+     * @param {!Array.<print_preview.Destination>} filteredDests Filtered list
+     *     of print destinations to render.
+     * @private
+     */
+    renderListWithNoMaxSize_: function(filteredDests) {
+      setIsVisible(this.noDestinationsMessageEl_, false);
+      if (filteredDests.length <= DestinationList.SHORT_LIST_SIZE_ ||
+          this.isShowAll_) {
+        filteredDests.forEach(function(dest) {
+          var destListItem = new print_preview.DestinationListItem(
+              this.eventTarget_, dest);
+          this.addChild(destListItem);
+          destListItem.render(this.destinationListItemContainer_);
+        }, this);
+        setIsVisible(this.footerEl_, false);
+      } else {
+        for (var dest, i = 0; i < DestinationList.SHORT_LIST_SIZE_ - 1; i++) {
+          var destListItem = new print_preview.DestinationListItem(
+              this.eventTarget_, filteredDests[i]);
+          this.addChild(destListItem);
+          destListItem.render(this.destinationListItemContainer_);
+        }
+        setIsVisible(this.footerEl_, true);
+        var totalCountEl = this.getElement().getElementsByClassName(
+            DestinationList.Classes_.TOTAL)[0];
+        totalCountEl.textContent =
+            localStrings.getStringF('destinationCount', filteredDests.length);
+      }
+    },
+
+    /**
+     * Called when the action link is clicked. Dispatches an
+     * ACTION_LINK_ACTIVATED event.
+     * @private
+     */
+    onActionLinkClick_: function() {
+      cr.dispatchSimpleEvent(
+          this, DestinationList.EventType.ACTION_LINK_ACTIVATED);
+    }
+  };
+
+  // Export
+  return {
+    DestinationList: DestinationList
+  };
+});