Fixed scrollbar not visible due to content being added a bit after mount, fixes #15711

packages/grafana-ui/src/components/CustomScrollbar/CustomScrollbar.tsx

@@ -15,6 +15,7 @@ interface Props {
   scrollTop?: number;
   setScrollTop: (event: any) => void;
   autoHeightMin?: number | string;
+  updateAfterMountMs?: number;
 }
 
 /**
@@ -48,6 +49,20 @@ export class CustomScrollbar extends Component<Props> {
 
   componentDidMount() {
     this.updateScroll();
+
+    // this logic is to make scrollbar visible when content is added body after mount
+    if (this.props.updateAfterMountMs) {
+      setTimeout(() => this.updateAfterMount(), this.props.updateAfterMountMs);
+    }
+  }
+
+  updateAfterMount() {
+    if (this.ref && this.ref.current) {
+      const scrollbar = this.ref.current as any;
+      if (scrollbar.update) {
+        scrollbar.update();
+      }
+    }
   }
 
   componentDidUpdate() {

public/app/features/dashboard/containers/DashboardPage.tsx

@@ -272,6 +272,7 @@ export class DashboardPage extends PureComponent<Props, State> {
             autoHeightMin={'100%'}
             setScrollTop={this.setScrollTop}
             scrollTop={scrollTop}
+            updateAfterMountMs={500}
             className="custom-scrollbar--page"
           >
             {editview && <DashboardSettings dashboard={dashboard} />}

public/app/features/dashboard/containers/__snapshots__/DashboardPage.test.tsx.snap

@@ -113,6 +113,7 @@ exports[`DashboardPage Dashboard init completed  Should render dashboard grid 1`
       hideTracksWhenNotNeeded={false}
       scrollTop={0}
       setScrollTop={[Function]}
+      updateAfterMountMs={500}
     >
       <div
         className="dashboard-container"
@@ -349,6 +350,7 @@ exports[`DashboardPage When dashboard has editview url state should render setti
       hideTracksWhenNotNeeded={false}
       scrollTop={0}
       setScrollTop={[Function]}
+      updateAfterMountMs={500}
     >
       <DashboardSettings
         dashboard={

public/app/features/dashboard/panel_editor/EditorTabBody.tsx

@@ -118,7 +118,7 @@ export class EditorTabBody extends PureComponent<Props, State> {
           {toolbarItems.map(item => this.renderButton(item))}
         </div>
         <div className="panel-editor__scroll">
-          <CustomScrollbar autoHide={false} scrollTop={scrollTop} setScrollTop={setScrollTop}>
+          <CustomScrollbar autoHide={false} scrollTop={scrollTop} setScrollTop={setScrollTop} updateAfterMountMs={300}>
             <div className="panel-editor__content">
               <FadeIn in={isOpen} duration={200} unmountOnExit={true}>
                 {openView && this.renderOpenView(openView)}