feedback (see commit description for details)

* fill blank space when no theme is selected
* animate row's height in themes/components list when selecting, and hide children list
* show warning when you move to a different page and have unsaved changes
* refactor `adminCustomizeThemes.show` controller
* allow collapsing/expanding children lists
* fix a bug when adding components to a theme (changed the way it works slightly)
* a bunch of other minor things

app/assets/javascripts/admin/routes/admin-customize-themes-edit.js.es6

@@ -35,5 +35,29 @@ export default Ember.Route.extend({
     controller.setTargetName(wrapper.target || "common");
     controller.set("fieldName", wrapper.field_name || "scss");
     this.controllerFor("adminCustomizeThemes").set("editingTheme", true);
+    this.set("shouldAlertUnsavedChanges", true);
+  },
+
+  actions: {
+    willTransition(transition) {
+      if (
+        this.get("controller.model.changed") &&
+        this.get("shouldAlertUnsavedChanges") &&
+        transition.intent.name !== this.routeName
+      ) {
+        transition.abort();
+        bootbox.confirm(
+          I18n.t("admin.customize.theme.unsaved_changes_alert"),
+          I18n.t("admin.customize.theme.discard"),
+          I18n.t("admin.customize.theme.stay"),
+          result => {
+            if (!result) {
+              this.set("shouldAlertUnsavedChanges", false);
+              transition.retry();
+            }
+          }
+        );
+      }
+    }
   }
 });

app/assets/javascripts/admin/routes/admin-customize-themes-index.js.es6

@@ -1,5 +1,25 @@
+const externalResources = [
+  {
+    key: "admin.customize.theme.beginners_guide_title",
+    link: "https://meta.discourse.org/t/91966",
+    icon: "book"
+  },
+  {
+    key: "admin.customize.theme.developers_guide_title",
+    link: "https://meta.discourse.org/t/93648",
+    icon: "book"
+  },
+  {
+    key: "admin.customize.theme.browse_themes",
+    link: "https://meta.discourse.org/c/theme",
+    icon: "paint-brush"
+  }
+];
+
 export default Ember.Route.extend({
-  setupController() {
+  setupController(controller, model) {
+    this._super(...arguments);
     this.controllerFor("adminCustomizeThemes").set("editingTheme", false);
+    controller.set("externalResources", externalResources);
   }
 });

app/assets/javascripts/admin/routes/admin-customize-themes-show.js.es6

@@ -37,9 +37,11 @@ export default Ember.Route.extend({
   },
 
   handleHighlight(theme) {
-    this.get("controller.allThemes").forEach(t => t.set("active", false));
+    this.get("controller.allThemes")
+      .filter(t => t.get("selected"))
+      .forEach(t => t.set("selected", false));
     if (theme) {
-      theme.set("active", true);
+      theme.set("selected", true);
     }
   },