right pane restoration for custom widgets

src/public/app/widgets/containers/right_pane_container.js

@@ -0,0 +1,27 @@
+import FlexContainer from "./flex_container.js";
+
+export default class RightPaneContainer extends FlexContainer {
+    constructor() {
+        super('column');
+
+        this.id('right-pane');
+        this.css('height', '100%');
+    }
+
+    isEnabled() {
+        return super.isEnabled() && this.children.length > 0 && !!this.children.find(ch => ch.isEnabled());
+    }
+
+    handleEventInChildren(name, data) {
+        const promise = super.handleEventInChildren(name, data);
+
+        if (['activeContextChanged', 'noteSwitchedAndActivated', 'noteSwitched'].includes(name)) {
+            // right pane is displayed only if some child widget is active
+            // we'll reevaluate the visibility based on events which are probable to cause visibility change
+            // but these events needs to be finished and only then we check
+            promise.then(() => this.toggleInt(this.isEnabled()));
+        }
+
+        return promise;
+    }
+}