Look at the attached movie.

I used this app:

import javafx.application.Application;
import javafx.scene.Group;
import javafx.scene.Scene;
import javafx.scene.control.ScrollPane;
import javafx.scene.layout.Pane;
import javafx.scene.paint.Color;
import javafx.scene.shape.Line;
import javafx.scene.shape.Rectangle;
import javafx.stage.Stage;

public class JavaApplication3 extends Application {

    public static void main(String[] args) {
        launch(args);
    }

    @Override
    public void start(Stage stage) throws Exception {
        Pane pane = new Pane();
        pane.setPrefSize(400, 400);

        ScrollPane sp = new ScrollPane();sp.setFocusTraversable(false);
        sp.setPrefSize(150, 150);
        sp.setContent(createCustomContent(200, 200));

        pane.getChildren().add(sp);

        Scene scene = new Scene(pane, 400, 400);
        stage.setScene(scene);
        stage.show();

    }

    public static Group createCustomContent(int height, int width) {
        Group res = new Group();

        Rectangle r = new Rectangle();
        r.setStroke(Color.BLACK);
        r.setStyle("-fx-border-color: GREEN;");

        res.getChildren().add(r);

        for (int i = 10; i < height; i += 10) {
            Line line1 = new Line(0, i, i - 5, i);
            Line line2 = new Line(i, 0, i, i - 5);
            Line line3 = new Line(i - 5, i, i - 5, height);
            Line line4 = new Line(i, i - 5, width, i - 5);

            line1.setStroke(Color.RED);
            line2.setStroke(Color.YELLOW);
            line3.setStroke(Color.BLUE);
            line4.setStroke(Color.MAGENTA);

            res.getChildren().addAll(line1, line2, line3, line4);
        }

        Rectangle rec = new Rectangle(0, 0, width, height);
        rec.setFill(Color.TRANSPARENT);
        rec.setStroke(Color.RED);

        res.getChildren().add(rec);

        return res;
    }
}