Print Preview: Making margin selection sticky (part 1/2).

chrome/browser/resources/print_preview/margin_settings.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() {
   'use strict';
 
   /**
    * Creates a Margins object that holds four margin values. The units in which
    * the values are expressed can be any numeric value.
@@ skipping 133 matching lines @@
     // @type {EventTracker} Used to keep track of certain event listeners.
     this.eventTracker_ = new EventTracker();
 
     this.addEventListeners_();
   }
 
   // Number of points per inch.
   MarginSettings.POINTS_PER_INCH = 72;
   // Minimum allowed distance in points between top-bottom, left-right margins.
   MarginSettings.MINIMUM_MARGINS_DISTANCE = 36;
-  // Margin list values.
+  // Margin list values. Matches enum MarginType in
+  // printing/print_job_constants.h.
   MarginSettings.MARGINS_VALUE_DEFAULT = 0;
   MarginSettings.MARGINS_VALUE_NO_MARGINS = 1;
-  MarginSettings.MARGINS_VALUE_CUSTOM = 2;
-  MarginSettings.MARGINS_VALUE_MINIMUM = 3;
-  // Default Margins option index.
-  MarginSettings.DEFAULT_MARGINS_OPTION_INDEX = 0;
+  MarginSettings.MARGINS_VALUE_MINIMUM = 2;
+  MarginSettings.MARGINS_VALUE_CUSTOM = 3;
+
+  // Indices in the dropdown correspoding to margins type.
+  MarginSettings.OPTION_INDEX_DEFAULT = 0;
+  MarginSettings.OPTION_INDEX_NO_MARGINS = 1;
+  MarginSettings.OPTION_INDEX_MINIMUM = 2;
+  MarginSettings.OPTION_INDEX_CUSTOM = 3;
+
   // Group name corresponding to the top margin.
   MarginSettings.TOP_GROUP = 'top';
   //  Group name corresponding to the left margin.
   MarginSettings.LEFT_GROUP = 'left';
   // Group name corresponding to the right margin.
   MarginSettings.RIGHT_GROUP = 'right';
   // Group name corresponding to the bottom margin.
   MarginSettings.BOTTOM_GROUP = 'bottom';
 
   /**
    * Extracts the number formatting and measurement system for the current
    * locale.
    * @param {string} numberFormat Is the formatted version of a sample number,
    *     sent from the backend.
    * @oaram {number} measurementSystem 0 for SI (aka metric system), 1 for the
    *     system used in the US. Note: Mathces UMeasurementSystem enum in
    *     third_party/icu/public/i18n/unicode/ulocdata.h.
    */
   MarginSettings.setNumberFormatAndMeasurementSystem = function(
       numberFormat, measurementSystem) {
     var regex = /^(\d+)(\.|\,)(\d+)(\.|\,)(\d+)$/;
     var matches = numberFormat.match(regex);
     MarginSettings.thousandsPoint = matches[2];
     MarginSettings.decimalPoint = matches[4];
     MarginSettings.useMetricSystem = measurementSystem == 0;
   };
 
+  /**
+   * @type {Object} Maps margin type values to indices within the drop-down
+   *     margin list.
+   */
+  MarginSettings.valueToIndex = {};

[kmadhusu, 2011/11/01 17:17:57]

Is there any specific reason to create this object? 
Index and the value are the same all the time. 

MarginSettings.valueToIndex[0] = 0;
MarginSettings.valueToIndex[1] = 1;
MarginSettings.valueToIndex[2] = 2;
MarginSettings.valueToIndex[3] = 3;

[dpapad, 2011/11/01 17:29:14]

It happens to be the same, but this is not a constraint. I did it this way to
allow for reordering the options in the dropdown without any other changes
needed. Otherwise reordering the options will also require to change the "value"
to match the index in 2 places (margin_settings.html and print_job_constants.h).

+  MarginSettings.valueToIndex[MarginSettings.MARGINS_VALUE_DEFAULT] =
+      MarginSettings.OPTION_INDEX_DEFAULT;
+  MarginSettings.valueToIndex[MarginSettings.MARGINS_VALUE_NO_MARGINS] =
+      MarginSettings.OPTION_INDEX_NO_MARGINS;
+  MarginSettings.valueToIndex[MarginSettings.MARGINS_VALUE_MINIMUM] =
+      MarginSettings.OPTION_INDEX_MINIMUM;
+  MarginSettings.valueToIndex[MarginSettings.MARGINS_VALUE_CUSTOM] =
+      MarginSettings.OPTION_INDEX_CUSTOM;
+
   cr.addSingletonGetter(MarginSettings);
 
   MarginSettings.prototype = {
     /**
      * Returns a dictionary of the four custom margin values.
      * @return {object}
      */
     get customMargins() {
       var margins = {};
       margins.marginLeft = this.customMargins_.left;
       margins.marginTop = this.customMargins_.top;
       margins.marginRight = this.customMargins_.right;
       margins.marginBottom = this.customMargins_.bottom;
       return margins;
     },
 
     /**
      * @return {number} The value of the selected margin option.
      */
     get selectedMarginsValue() {
       var val = this.marginList_.options[this.marginList_.selectedIndex].value;
       return parseInt(val, 10);
     },
 
     /**
+     * @param {number} The index to be selected within |this.marginList_|.
+     */
+    set selectedMarginsIndex(index) {
+      this.marginList_.selectedIndex = index;
+    },
+
+    /**
      * @return {number} The total width of the plugin in points.
      */
     get totalWidthInPoints() {
       var pageInformation = previewArea.pageLocationNormalized;
       return this.pageWidth_ / pageInformation.width;
     },
 
     /**
      * @return {number} The total height of the plugin in points.
      */
@@ skipping 366 matching lines @@
     },
 
     /**
      * If custom margins is the currently selected option then change to the
      * default margins option.
      * @private
      */
     resetMarginsIfNeeded: function() {
       if (this.isCustomMarginsSelected()) {
         this.marginList_.options[
-            MarginSettings.DEFAULT_MARGINS_OPTION_INDEX].selected = true;
+            MarginSettings.OPTION_INDEX_DEFAULT].selected = true;
         this.removeCustomMarginEventListeners_();
         this.forceDisplayingMarginLines_ = true;
         this.lastSelectedOption_ = MarginSettings.MARGINS_VALUE_DEFAULT;
       }
     },
 
     /**
      * Executes when a |customEvents.PDF_LOADED| event occurs.
      * @private
      */
     onPDFLoaded_: function() {
       if (!previewModifiable)
         fadeOutOption(this.marginsOption_);
     }
   };
 
   return {
     MarginSettings: MarginSettings,
     PageLayout: PageLayout,
     setNumberFormatAndMeasurementSystem:
         MarginSettings.setNumberFormatAndMeasurementSystem,
   };
 });