import javafx.application.Application;
import javafx.beans.InvalidationListener;
import javafx.beans.Observable;
import javafx.scene.Group;
import javafx.scene.Node;
import javafx.scene.Scene;
import javafx.scene.control.ScrollPane;
import javafx.scene.control.Tab;
import javafx.scene.control.TabPane;
import javafx.scene.control.TitledPane;
import javafx.scene.layout.StackPane;
import javafx.scene.shape.Rectangle;
import javafx.stage.Stage;

public class Test extends Application {

    private Scene scene = null;

    public static void main(String[] args) {
        Application.launch(Test.class, (String[]) null);
    }

    public void start(Stage stage) {

        scene = new Scene(new Group());
        scene.getStylesheets().add(Test.class.getResource("test.css").toExternalForm());

        stage.setTitle("TEST");
        stage.setWidth(500);
        stage.setHeight(500);
        stage.setScene(scene);
        stage.show();

        final TitledPane titledPane = new TitledPane("Title", null);
        titledPane.setContent(new Rectangle(50, 200));
        titledPane.setMaxWidth(Long.MAX_VALUE);
        titledPane.setMinWidth(0);

        final StackPane stackPane1 = new StackPane();
        stackPane1.getChildren().add(titledPane);

        final ScrollPane scrollPane = new ScrollPane();
        scrollPane.setFitToWidth(true);
        scrollPane.setContent(stackPane1);

        scrollPane.viewportBoundsProperty().addListener(new InvalidationListener() {

            @Override
            public void invalidated(Observable observable) {
                final Node content = scrollPane.getContent();
                final double viewPortHeight = scrollPane.getViewportBounds().getHeight();
                final double contentHeight = content.prefHeight(0);
                final boolean isScrollBarVisible = (viewPortHeight < contentHeight);

                if (isScrollBarVisible) { // Scroll bar is visible
                    content.getStyleClass().remove("scrollBarNotVisible");
                    // Check css rule has not been already added
                    if (!content.getStyleClass().contains("scrollBarVisible")) {
                        content.getStyleClass().add("scrollBarVisible");
                    }
                } else { // Scroll bar is not visible
                    content.getStyleClass().remove("scrollBarVisible");
                    // Check css rule has not been already added
                    if (!content.getStyleClass().contains("scrollBarNotVisible")) {
                        content.getStyleClass().add("scrollBarNotVisible");
                    }
                }
            }
        });

        final StackPane stackPane2 = new StackPane();
        stackPane2.getChildren().add(scrollPane);

        final TabPane tabPane = new TabPane();
        Tab tab = new Tab();
        tab.setText("Tab");
        tab.setContent(stackPane2);
        tabPane.getTabs().addAll(tab);

        ((Group) scene.getRoot()).getChildren().addAll(tabPane);
    }
}