I hope the code comment is self explaining.


import javafx.application.Application;
import javafx.scene.Scene;
import javafx.scene.chart.LineChart;
import javafx.scene.chart.NumberAxis;
import javafx.stage.Stage;

public class RunTest extends Application {

@Override
public void start(Stage primaryStage) throws Exception {
primaryStage.setScene(new Scene(new LineChart<>(new NumberAxis(), new NumberAxis())));
primaryStage.show();
primaryStage.centerOnScreen();
int parentPositionY = (int) primaryStage.getScene().getRoot().localToScreen(0, 0).getY();

System.out.println(parentPositionY);
// Win7, Screen: 1600x900
// ===============================================
// Real screen-Y of root is 170 with 8u51
// parentPositionY is 170 with 8u51
// ===============================================
// Real screen-Y of root is 171 with 8u60
// parentPositionY is 170 with 8u60 !!!!!!!!!!!!!!
}

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

}