title: how to make child auto-resize (child is Pane, parent is VBox) in javafx
body: <p>I have 2 questions</p>
  
  <p>1.in a javafx application, I want to put the child(crosshairArea) at the left-top corner of its parent, with 1/2 width and height as well.
  think I can do that via override the parent function "layoutChildren" (VBox), 
  is there other way to do that? e.g. property binding?</p>
  
  <p>2.initially VBox will occupy the full scene area, how to make(relocate) it to the half-bottom of scene?</p>
  
  <pre><code>public class Crossh extends Application {
  
      public static void main(String[] args) {
          launch(args);
      }
  
      @Override
      public void start(Stage stage) {        
          VBox root = new VBox(5);
          // root.setPadding(new Insets(20,20,20,20));
          root.setStyle("-fx-border-color:red");
  
          Pane crosshairArea = new Pane();
          crosshairArea.maxWidthProperty().bind(root.widthProperty());
          crosshairArea.setStyle("-fx-border-color:black");       
  
          root.getChildren().add(crosshairArea);
          Scene scene = new Scene(root);
          stage.setScene(scene);
          stage.setTitle("Location Crosshair");
          stage.setWidth(900);
          stage.setHeight(700);        
          stage.show();
      }
  }
  </code></pre>