When Labeled.getClassCssMetaData() gets touched the first time a sideaffect appears.
A region without borders suddenly gets a new background with a bright grey color.

A workaround is, to touch Labeled.getClassCssMetaData() at the start of the application, so that Region keeps the same behaviour during the whole runtime, instead of switching on the first touch.

I assume, that the touch intializes the css engine.

See the sample program below.


package bug;

import javafx.application.Application;
import javafx.event.EventHandler;
import javafx.scene.Scene;
import javafx.scene.control.Labeled;
import javafx.scene.input.MouseEvent;
import javafx.scene.layout.Region;
import javafx.scene.paint.Color;
import javafx.stage.Stage;

public class TouchingLabeled extends Application {
    public static void main(String[] args) {
        launch(args);
    }
    public void start(Stage primaryStage) {
        //Labeled.getClassCssMetaData(); //workaround
        Region reg = new Region();
        reg.onMouseClickedProperty().set(new EventHandler<MouseEvent>() {
            @Override
            public void handle(MouseEvent event) {
                Labeled.getClassCssMetaData();
            }
        });
        System.out.println(System.getProperty("java.version"));

        primaryStage.setScene(new Scene(reg, 300, 250, Color.BLUE));
        primaryStage.show();
    }
}