import java.util.Random;
import javafx.application.Application;
import javafx.event.EventHandler;
import javafx.scene.SceneBuilder;
import javafx.scene.control.ScrollPaneBuilder;
import javafx.scene.input.KeyEvent;
import javafx.scene.layout.VBox;
import javafx.scene.layout.VBoxBuilder;
import javafx.scene.paint.Color;
import javafx.scene.shape.RectangleBuilder;
import javafx.stage.Stage;
import javafx.stage.StageBuilder;


/**
 *
 * @author akouznet
 */
public class Bug extends Application {
    
    public static void main(String[] args) {
        launch(args);
    }
    
    private VBox vBox;
    private Random r = new Random();

    @Override
    public void start(Stage stage) throws Exception {
        
        StageBuilder.create()
                .scene(
                    SceneBuilder.create()
                        .width(300)
                        .height(300)
                        .onKeyPressed(new EventHandler<KeyEvent>() {

                            @Override
                            public void handle(KeyEvent t) {
                                vBox.getChildren().add(RectangleBuilder.create()
                                        .width(r.nextInt(150) + 50)
                                        .height(r.nextInt((int) vBox.getHeight() / 3 + 10))
                                        .fill(Color.rgb(r.nextInt(256), r.nextInt(256), r.nextInt(256)))
                                        .build());
                            }
                        })
                        .root(ScrollPaneBuilder.create()
                            .pannable(true)
                            .content(vBox = VBoxBuilder.create()
                                .build())
                            .build())
                        .build())
                .applyTo(stage);
        stage.show(); 
    }
    
}