Implement smoother autosizing of the extension options overlay

chrome/browser/resources/extensions/extension_options_overlay.js

 // Copyright 2014 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('extensions', function() {
   'use strict';
 
   /**
    * The ExtensionOptionsOverlay will show an extension's options page using
    * an <extensionoptions> element.
@@ skipping 45 matching lines @@
     },
 
     /**
      * Associate an extension with the overlay and display it.
      * @param {string} extensionId The id of the extension whose options page
      *     should be displayed in the overlay.
      * @param {string} extensionName The name of the extension, which is used
      *     as the header of the overlay.
      */
     setExtensionAndShowOverlay: function(extensionId, extensionName) {
+      $('extension-options-overlay-title').textContent = extensionName;
+
       var extensionoptions = new ExtensionOptions();
       extensionoptions.extension = extensionId;
       extensionoptions.autosize = 'on';
 
+      // The <extensionoptions> content's size needs to be restricted to the
+      // bounds of the overlay window. The overlay gives a min width and
+      // max height, but the maxheight does not include our header height
+      // (title and close button), so we need to subtract that to get the
+      // max height for the extension options.
+      var headerHeight = $('extension-options-overlay-title').offsetHeight;
+      var overlayMaxHeight =
+          parseInt($('extension-options-overlay').style.maxHeight);
+      extensionoptions.maxheight = overlayMaxHeight - headerHeight;
+
+      extensionoptions.minwidth =
+          parseInt(window.getComputedStyle($('extension-options-overlay'))
+              .minWidth);
+
+      extensionoptions.setDeferAutoSize(true);
+
       extensionoptions.onclose = function() {
         this.handleDismiss_();
       }.bind(this);
 
-      // TODO(ericzeng): Resize in a non-jarring way.
+      // Resize the overlay if the <extensionoptions> changes size.
       extensionoptions.onsizechanged = function(evt) {
-        $('extension-options-overlay').style.width = evt.width;
-        $('extension-options-overlay').style.height = evt.height;
+        var overlayStyle =
+            window.getComputedStyle($('extension-options-overlay'));
+        var oldWidth = parseInt(overlayStyle.width);
+        var oldHeight = parseInt(overlayStyle.height);
+
+        // animationTime is the amount of time in ms that will be used to resize
+        // the overlay. It is calculated by multiplying the pythagorean distance
+        // between old and the new size (in px) with a constant speed of
+        // 0.25 ms/px.
+        var animationTime = 0.25 * Math.sqrt(
+            Math.pow(evt.newWidth - oldWidth, 2) +
+            Math.pow(evt.newHeight - oldHeight, 2));
+
+        var player = $('extension-options-overlay').animate([
+          {width: oldWidth + 'px', height: oldHeight + 'px'},
+          {width: evt.newWidth + 'px', height: evt.newHeight + 'px'}
+        ], {
+          duration: animationTime,
+          delay: 0
+        });
+
+        player.onfinish = function(e) {
+          // Allow the <extensionoptions> to autosize now that the overlay
+          // has resized, and move it back on-screen.
+          extensionoptions.resumeDeferredAutoSize();
+          $('extension-options-overlay-guest').style.position = 'static';
+          $('extension-options-overlay-guest').style.left = 'auto';
+        };
       }.bind(this);
 
+      // Don't allow the <extensionoptions> to autosize until the overlay
+      // animation is complete.
+      extensionoptions.setDeferAutoSize(true);
+
+      // Move the <extensionoptions> off screen until the overlay is ready
+      $('extension-options-overlay-guest').style.position = 'fixed';
+      $('extension-options-overlay-guest').style.left =
+          window.outerWidth + 'px';
+
       $('extension-options-overlay-guest').appendChild(extensionoptions);
-
-      $('extension-options-overlay-title').textContent = extensionName;
-
       this.setVisible_(true);
     },
 
     /**
      * Toggles the visibility of the ExtensionOptionsOverlay.
      * @param {boolean} isVisible Whether the overlay should be visible.
      * @private
      */
     setVisible_: function(isVisible) {
       this.showOverlay_(isVisible ? $('extension-options-overlay') : null);
     }
   };
 
   // Export
   return {
     ExtensionOptionsOverlay: ExtensionOptionsOverlay
   };
 });