MD Settings: refactor some main page properties, fix Advanced toggle

chrome/browser/resources/settings/settings_main/settings_main.js

Index: chrome/browser/resources/settings/settings_main/settings_main.js
diff --git a/chrome/browser/resources/settings/settings_main/settings_main.js b/chrome/browser/resources/settings/settings_main/settings_main.js
index a5a6d10c5c551c74e652076ad17224e1cae42f98..3fd909a7b4cea708944036d56deb48b72edf93d0 100644
--- a/chrome/browser/resources/settings/settings_main/settings_main.js
+++ b/chrome/browser/resources/settings/settings_main/settings_main.js
@@ -10,12 +10,6 @@ Polymer({
   is: 'settings-main',
 
   properties: {
-    /** @private */
-    isAdvancedMenuOpen_: {
-      type: Boolean,
-      value: false,
-    },
-
     /**
      * Preferences state.
      */
@@ -35,28 +29,22 @@ Polymer({
     },
 
     /** @private */
-    showAdvancedPage_: {
+    advancedToggleExpanded_: {
       type: Boolean,
       value: false,
     },
 
     /** @private */
-    showAdvancedToggle_: {
-      type: Boolean,
-      value: true,
-    },
+    inSubpage_: Boolean,
 
     /** @private */
-    showBasicPage_: {
-      type: Boolean,
-      value: true,
-    },
+    showAboutPage_: Boolean,
 
     /** @private */
-    showAboutPage_: {
-      type: Boolean,
-      value: false,
-    },
+    showBasicPage_: Boolean,
+
+    /** @private */
+    showAdvancedPage_: Boolean,
 
     toolbarSpinnerActive: {
       type: Boolean,
@@ -82,14 +70,13 @@ Polymer({
   /** @override */
   attached: function() {
     document.addEventListener('toggle-advanced-page', function(e) {
-      this.showAdvancedPage_ = e.detail;
-      this.isAdvancedMenuOpen_ = e.detail;
+      this.advancedToggleExpanded_ = e.detail;
       this.currentRoute = {
-        page: this.isAdvancedMenuOpen_ ? 'advanced' : 'basic',
+        page: this.advancedToggleExpanded_ ? 'advanced' : 'basic',
         section: '',
         subpage: [],
       };
-      if (this.showAdvancedPage_) {
+      if (this.advancedToggleExpanded_) {
         doWhenReady(
             function() {
               var advancedPage = this.$$('settings-advanced-page');
@@ -115,7 +102,7 @@ Polymer({
    * @param {boolean} opened Whether the menu is expanded.
    * @return {string} Which icon to use.
    * @private
-   * */
+   */
   arrowState_: function(opened) {
     return opened ? 'settings:arrow-drop-up' : 'cr:arrow-drop-down';
   },
@@ -125,24 +112,26 @@ Polymer({
    * @private
    */
   currentRouteChanged_: function(newRoute) {
-    var isSubpage = !!newRoute.subpage.length;
-
+    this.inSubpage_ = newRoute.subpage.length > 0;
     this.showAboutPage_ = newRoute.page == 'about';

[dpapad, 2016/07/20 21:30:08]

Drive-by question: Would it make more sense to package the three booleans to a
single Polymer property?

showingPages_: {
  type: Boolean,
  value: {basic: false, advanced: false, about: false},
}

This way you can replace all 3 booleans at once, instead of flipping them one by
one. Maybe that invokes less DOM updates?

[michaelpg, 2016/07/20 22:25:39]

Fine idea, done.

+    if (this.showAboutPage_) {
+      this.showBasicPage_ = this.showAdvancedPage_ = false;
+    } else if (newRoute.page == 'basic') {
+      this.showBasicPage_ = true;
+      this.showAdvancedPage_ = !this.inSubpage_ && this.advancedToggleExpanded_;
+    } else if (newRoute.page == 'advanced') {
+      this.showBasicPage_ = !this.inSubpage_;
+      this.showAdvancedPage_ = this.advancedToggleExpanded_ = true;
+    } else {
+      assertNotReached('Invalid page ' + newRoute.page);
+    }
 
-    this.showAdvancedToggle_ = !this.showAboutPage_ && !isSubpage;
-
-    this.showBasicPage_ = this.showAdvancedToggle_ || newRoute.page == 'basic';
-
-    this.showAdvancedPage_ =
-        (this.isAdvancedMenuOpen_ && this.showAdvancedToggle_) ||
-        newRoute.page == 'advanced';
-
-    this.style.height = isSubpage ? '100%' : '';
+    this.style.height = this.inSubpage_ ? '100%' : '';
   },
 
   /** @private */
   toggleAdvancedPage_: function() {
-    this.fire('toggle-advanced-page', !this.isAdvancedMenuOpen_);
+    this.fire('toggle-advanced-page', !this.advancedToggleExpanded_);
   },
 
   /**