MD Settings: Save and restore scroll position in iron-list

chrome/browser/resources/settings/bluetooth_page/bluetooth_page.js

 // Copyright 2015 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
  * 'settings-bluetooth-page' is the settings page for managing bluetooth
  *  properties and devices.
  *
  * Example:
@@ skipping 62 matching lines @@
      * @private
      */
     deviceList_: {
       type: Array,
       value: function() {
         return [];
       },
     },
 
     /**
+     * The ordered list of paired or connecting bluetooth devices.
+     * @type {!Array<!chrome.bluetooth.Device>}
+     */
+    pairedDeviceList_: {
+      type: Array,
+      value: /** @return {Array} */ function() {
+        return [];
+      },
+    },
+
+    /**
      * Reflects the iron-list selecteditem property.
      * @type {!chrome.bluetooth.Device}
      * @private
      */
     selectedItem_: {
       type: Object,
       observer: 'selectedItemChanged_',
     },
 
     /**
@@ skipping 128 matching lines @@
 
   /** @private */
   bluetoothEnabledChanged_: function() {
     // When bluetooth is enabled, auto-expand the device list.
     if (this.bluetoothEnabled_)
       this.deviceListExpanded_ = true;
   },
 
   /** @private */
   deviceListChanged_: function() {
+    var devices = this.$.devices;

[Dan Beam, 2017/02/01 06:13:17]

what's the point of this var?  |this| wont change here, afaict...

[stevenjb, 2017/02/02 01:17:47]

We use it twice below... Not sure I understand the question. I guess you're
saying that this.$.devices isn't long enough to merit the use of a local? Sounds
like a nit, but yeah, sure.

+    this.saveScroll(devices);
+    this.pairedDeviceList_ = this.deviceList_.filter(function(device) {
+      return !!device.paired || !!device.connecting;
+    });
+    this.updateScrollableContents();
+    this.restoreScroll(devices);
+
     for (var i = 0; i < this.deviceList_.length; ++i) {
       if (this.deviceList_[i].connected) {
         this.deviceConnected_ = true;
         return;
       }
     }
     this.deviceConnected_ = false;
   },
 
   /** @private */
@@ skipping 41 matching lines @@
    * this.deviceList_.
    * @private
    */
   updateDeviceList_: function() {
     if (!this.bluetoothEnabled_) {
       this.deviceList_ = [];
       return;
     }
     this.bluetooth.getDevices(function(devices) {
       this.deviceList_ = devices;
-      this.updateScrollableContents();
     }.bind(this));
   },
 
   /**
    * Event called when a user action changes the bluetoothEnabled state.
    * @private
    */
   onBluetoothEnabledChange_: function() {
     this.bluetoothPrivate.setAdapterState(
         {powered: this.bluetoothEnabled_}, function() {
@@ skipping 176 matching lines @@
   /**
    * @param {!chrome.bluetooth.Device} device
    * @return {string} The text to display for |device| in the device list.
    * @private
    */
   getDeviceName_: function(device) {
     return device.name || device.address;
   },
 
   /**
-   * @return {!Array<!chrome.bluetooth.Device>}
-   * @private
-   */
-  getPairedOrConnecting_: function() {
-    return this.deviceList_.filter(function(device) {
-      return !!device.paired || !!device.connecting;
-    });
-  },
-
-  /**
    * @return {boolean} True if deviceList contains any paired devices.
    * @private
    */
   haveDevices_: function() {
     return this.deviceList_.findIndex(function(d) {
       return !!d.paired;
     }) != -1;
   },
 
   /**
@@ skipping 109 matching lines @@
   },
 
   /**
    * @param {Event} e
    * @private
    */
   stopTap_: function(e) {
     e.stopPropagation();
   },
 });