JavaFX Area Charts and adding dynamic labels following cursor - layout

Question

I'd like to to be able to add a label to a chart that follows the cursor. I've already seen several examples of this on stack overflow already that attach labels to the values/nodes of a series but I want to be able to do this for the whole of the area chart. My problem comes when I want to add a label (ultimately a floating box of values). I'm struggling to figure out how I can do this and maintain the layout of the scene. When I add the chart to the scene as the dedicated item the chart renders as expected. But when I add a label to the scene it is shared and the chart no longer fills the entire canvas
Group root = new Group();
root.getChildren().addAll(sac,myLabel);
Scene scene = new Scene(root, 800, 600); // Now the Chart shares the scene with the label
I want to add the label so I can use it as the mouse moves over a chart and then simply translate it to the cursor position. I've no problem with the mouse events just that I can't seem to share a scene with objects that are transient. I believe this is down to a lack of understanding on how to manage this particular situation. It's entirely likely the solution to this problem is to dynamically generate this label and not have it as a static scene object. Any help gratefully received.
Full test case below (Java 8)
import javafx.application.Application;
import javafx.scene.Group;
import javafx.scene.Node;
import javafx.scene.Scene;
import javafx.scene.chart.NumberAxis;
import javafx.scene.chart.StackedAreaChart;
import javafx.scene.chart.XYChart;
import javafx.scene.control.Label;
import javafx.scene.input.MouseEvent;
import javafx.stage.Stage;
public class AreaChartTestCase extends Application {
final NumberAxis xAxis = new NumberAxis(1, 31, 1);
final NumberAxis yAxis = new NumberAxis();
final StackedAreaChart<Number, Number> sac
= new StackedAreaChart<Number, Number>(xAxis, yAxis);
Label myLabel = new Label();
#Override
public void start(Stage stage) {
stage.setTitle("Area Chart Sample");
sac.setTitle("Temperature Monitoring (in Degrees C)");
XYChart.Series<Number, Number> seriesApril
= new XYChart.Series<Number, Number>();
seriesApril.setName("April");
seriesApril.getData().add(new XYChart.Data(1, 4));
seriesApril.getData().add(new XYChart.Data(3, 10));
seriesApril.getData().add(new XYChart.Data(6, 15));
seriesApril.getData().add(new XYChart.Data(9, 8));
seriesApril.getData().add(new XYChart.Data(12, 5));
seriesApril.getData().add(new XYChart.Data(15, 18));
seriesApril.getData().add(new XYChart.Data(18, 15));
seriesApril.getData().add(new XYChart.Data(21, 13));
seriesApril.getData().add(new XYChart.Data(24, 19));
seriesApril.getData().add(new XYChart.Data(27, 21));
seriesApril.getData().add(new XYChart.Data(30, 21));
XYChart.Series<Number, Number> seriesMay
= new XYChart.Series<Number, Number>();
seriesMay.setName("May");
seriesMay.getData().add(new XYChart.Data(1, 20));
seriesMay.getData().add(new XYChart.Data(3, 15));
seriesMay.getData().add(new XYChart.Data(6, 13));
seriesMay.getData().add(new XYChart.Data(9, 12));
seriesMay.getData().add(new XYChart.Data(12, 14));
seriesMay.getData().add(new XYChart.Data(15, 18));
seriesMay.getData().add(new XYChart.Data(18, 25));
seriesMay.getData().add(new XYChart.Data(21, 25));
seriesMay.getData().add(new XYChart.Data(24, 23));
seriesMay.getData().add(new XYChart.Data(27, 26));
seriesMay.getData().add(new XYChart.Data(31, 26));
final Node chartPlotBackground = sac.lookup(".chart-plot-background");
chartPlotBackground.setOnMouseEntered((MouseEvent mouseEvent) -> {
myLabel.setVisible(true);
});
chartPlotBackground.setOnMouseExited((MouseEvent mouseEvent) -> {
myLabel.setVisible(false);
});
chartPlotBackground.setOnMouseMoved((MouseEvent mouseEvent) -> {
myLabel.setText("Location : X = " + mouseEvent.getSceneX() + " : Y = "+ mouseEvent.getSceneY());
myLabel.setTranslateX(mouseEvent.getSceneX());
myLabel.setTranslateY(mouseEvent.getSceneY());
});
Group root = new Group();
root.getChildren().addAll(sac, myLabel);
Scene scene = new Scene(root, 800, 600); // Now the Chart shares the scene with the label
sac.getData().addAll(seriesApril, seriesMay);
stage.setScene(scene);
stage.show();
}
public static void main(String[] args) {
launch(args);
}
}

Answer 1

So I think I've solved it. At least to a level that meets my requirements.
Group root = new Group();
root.setManaged(false);
root.getChildren().add(ac);
root.getChildren().add(myLabel);
Scene scene = new Scene(root);
scene.widthProperty().addListener(new ChangeListener<Number>() {
#Override
public void changed(ObservableValue<? extends Number> observableValue, Number oldSceneWidth, Number newSceneWidth) {
ac.setPrefWidth((double) newSceneWidth);
}
});
scene.heightProperty().addListener(new ChangeListener<Number>() {
#Override
public void changed(ObservableValue<? extends Number> observableValue, Number oldSceneHeight, Number newSceneHeight) {
ac.setPrefHeight((double) newSceneHeight);
}
});
By listening to changes in the width and height properties and manually managing the layout of the chart and label I was able to get the layout and functionality I required.I'm not 100% sure if this the optimal approach but it works.