diff --git a/egui_demo_lib/src/apps/demo/painting.rs b/egui_demo_lib/src/apps/demo/painting.rs
index 61efed1c..2e4d2072 100644
--- a/egui_demo_lib/src/apps/demo/painting.rs
+++ b/egui_demo_lib/src/apps/demo/painting.rs
@@ -18,24 +18,24 @@ impl Default for Painting {
 }
 
 impl Painting {
-    pub fn ui_control(&mut self, ui: &mut Ui) {
+    pub fn ui_control(&mut self, ui: &mut egui::Ui) -> egui::Response {
         ui.horizontal(|ui| {
             egui::stroke_ui(ui, &mut self.stroke, "Stroke");
             ui.separator();
             if ui.button("Clear Painting").clicked() {
                 self.lines.clear();
             }
-        });
+        })
+        .response
     }
 
-    pub fn ui_content(&mut self, ui: &mut Ui) {
-        let (response, painter) =
+    pub fn ui_content(&mut self, ui: &mut Ui) -> egui::Response {
+        let (mut response, painter) =
             ui.allocate_painter(ui.available_size_before_wrap_finite(), Sense::drag());
-        let rect = response.rect;
 
         let to_screen = emath::RectTransform::from_to(
-            Rect::from_min_size(Pos2::ZERO, rect.square_proportions()),
-            rect,
+            Rect::from_min_size(Pos2::ZERO, response.rect.square_proportions()),
+            response.rect,
         );
         let from_screen = to_screen.inverse();
 
@@ -49,17 +49,23 @@ impl Painting {
             let canvas_pos = from_screen * pointer_pos;
             if current_line.last() != Some(&canvas_pos) {
                 current_line.push(canvas_pos);
+                response.mark_changed();
             }
         } else if !current_line.is_empty() {
             self.lines.push(vec![]);
+            response.mark_changed();
         }
 
+        let mut shapes = vec![];
         for line in &self.lines {
             if line.len() >= 2 {
                 let points: Vec<Pos2> = line.iter().map(|p| to_screen * *p).collect();
-                painter.add(Shape::line(points, self.stroke));
+                shapes.push(egui::Shape::line(points, self.stroke));
             }
         }
+        painter.extend(shapes);
+
+        response
     }
 }