Print Preview: Making margin lines draggable.

chrome/browser/resources/print_preview/preview_area.js

 // Copyright (c) 2011 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() {
   'strict';
 
   /**
    * Creates a PreviewArea object. It represents the area where the preview
    * document is displayed.
    * @constructor
    */
   function PreviewArea() {
     // The embedded pdf plugin object.
     this.pdfPlugin_ = null;
 
     // True if the pdf document is loaded in the preview area.
     this.pdfLoaded_ = false;
 
     // Contains the zoom level just before a new preview is requested so the
     // same zoom level can be restored.
     this.zoomLevel_ = null;
     // @type {{x: number, y: number}} Contains the page offset values just
     //     before a new preview is requested so that the scroll amount can be
     //     restored later.
     this.pageOffset_ = null;
+
+    // @type {print_preview.Rect} A rectangle describing the postion of the
+    // most visible page normalized with respect to the total height and width
+    // of the plugin.
+    this.pageLocationNormalized = null;
+
     this.addEventListeners_();
   }
 
   cr.addSingletonGetter(PreviewArea);
 
   PreviewArea.prototype = {
     /**
      * The width of the plugin area in pixels, excluding any visible scrollbars,
      * @type {number}
      */
@@ skipping 34 matching lines @@
 
     get pdfLoaded() {
       return this.pdfLoaded_;
     },
 
     set pdfLoaded(pdfLoaded) {
       this.pdfLoaded_ = pdfLoaded;
     },
 
     /**
-     * @return {print_preview.Rect} A rectangle describing the postion of the
-     *   most visible page normalized with respect to the total height and width
-     *   of the plugin.
+     * Queries the plugin for the location of the most visible page and updates
+     * |this.pageLocationNormalized|.
      */
-    getPageLocationNormalized: function() {
+    update: function() {
+      if (!this.pdfLoaded_)
+        return;
       var pluginLocation =
           this.pdfPlugin_.getPageLocationNormalized().split(';');
-      return new print_preview.Rect(parseFloat(pluginLocation[0]),
-                                    parseFloat(pluginLocation[1]),
-                                    parseFloat(pluginLocation[2]),
-                                    parseFloat(pluginLocation[3]));
+      this.pageLocationNormalized = new print_preview.Rect(
+          parseFloat(pluginLocation[0]),
+          parseFloat(pluginLocation[1]),
+          parseFloat(pluginLocation[2]),
+          parseFloat(pluginLocation[3]));
     },
 
     /**
      * Resets the state variables of |this|.
      */
     resetState: function() {
       if (this.pdfPlugin_) {
         this.zoomLevel_ = this.pdfPlugin_.getZoomLevel();
         this.pageOffset_ = {
             x: this.pdfPlugin_.pageXOffset(),
@@ skipping 26 matching lines @@
       } else {
         this.pdfPlugin_.fitToHeight();
       }
     }
   };
 
   return {
     PreviewArea: PreviewArea,
   };
 });