Wrong results when trying to get sizes of a pane with css-formattings - javafx-2

Question

I came across a strange behaviour of JavaFX when i tried to obtain the bordersizes (bounds) of a pane that has some css-effects//formattings applied to it. In my application i have to lookup the exact sizes of different objects in order to connect them with lines (imagine some sort of UML-diagramm editor, the start and endpoints of the lines are the border coordinates of the objects).
Now to my problem: whenever i try to get the bordersizes of an object in the same method where this object is put on the scene graph, the result does not include any css attributes like padding, bordersize, strokes and so on. The exact result gets returned if the object already exists on the scene graph before i lookup the size. It seems to be that JavaFX has to wait for one rendering pass (16,7ms) to actually update the real bounds and sizes on an object. Is there any way to get the size of an object (especially those which extend Pane) in the same method as it is created? I don't really like the workaround with waiting for 16,7ms, because it creates some unwanted behaviour in my application.
The following code shows the problem. The size when creating the pane containing the rectangle does not equal the size when pressing the "show size" button.
public class SzenarioView extends GridPane
{
private Group paintingLayer;
public SzenarioView()
{
super();
paintingLayer = new Group();
paintingLayer.getStylesheets().add(TestStarter.class.getResource("ReprBox.css").toString());
Rectangle r1 = new Rectangle(0, 0, 1000, 1000);
r1.setFill(Color.AZURE);
paintingLayer.getChildren().add(r1);
Button b1 = new Button("Show Size");
b1.setOnAction(new EventHandler<ActionEvent>() {
#Override
public void handle(ActionEvent arg0) {
for(Node n : paintingLayer.getChildren())
{
System.out.println("Border...");
System.out.println(getNodeBorderCoords(n, BorderTypes.RIGHT)[0]);
System.out.println(getNodeBorderCoords(n, BorderTypes.RIGHT)[1]);
System.out.println("End Border");
}
}
});
Button b2 = new Button("Add CCSBTN");
b2.setOnAction(new EventHandler<ActionEvent>() {
#Override
public void handle(ActionEvent event) {
BorderPane bp = new BorderPane();
bp.getStylesheets().add(TestStarter.class.getResource("ReprBox.css").toString());
Rectangle rcss = new Rectangle(50, 50);
bp.setTop(rcss);
bp.getStyleClass().add("my-box");
setObjectOnScreen(bp, 100, 100);
System.out.println(getNodeBorderCoords(bp, BorderTypes.RIGHT)[0]);
System.out.println(getNodeBorderCoords(bp, BorderTypes.RIGHT)[1]);
}
});
this.add(b1, 0, 0);
this.add(b2, 1, 0);
this.add(paintingLayer, 1, 1);
this.setMaxHeight(500);
this.setMaxWidth(700);
this.setHgap(10);
this.setVgap(10);
this.setPadding(new Insets(10, 10, 10, 10));
}
public void setObjectOnScreen(Node obj, double toX, double toY)
{
obj.setLayoutX(toX);
obj.setLayoutY(toY);
paintingLayer.getChildren().add(obj);
}
public double[] getNodeBorderCoords(Node n, BorderTypes type)
{
double x = 0;
double y = 0;
double bx = n.getBoundsInLocal().getWidth();
double by = n.getBoundsInLocal().getHeight();
switch (type)
{
case LEFT:
x = n.getLayoutX();
y = n.getLayoutY() + by / 2;
break;
case RIGHT:
x = n.getLayoutX() + bx ;
y = n.getLayoutY() + by / 2;
break;
case TOP:
x = n.getLayoutX() + bx / 2;
y = n.getLayoutY();
break;
case BOTTOM:
x = n.getLayoutX() + bx / 2;
y = n.getLayoutY() + by;
break;
}
double[] ret =
{ x, y, };
return ret;
}
}
The CSS-File
#CHARSET "ISO-8859-1";
.my-box {
-fx-border-color: rgb(255, 0, 0);
-fx-border-radius: 2;
-fx-padding: 1 1 1 1;
-fx-border-width: 5 5 5 5;
}
By the way, it doesn't matter if use getBoundsInLocal() or getBoundsInParent() .
UPDATE
Here are two workarounds that can be used:
Thread t = new Thread(new Runnable() {
#Override
public void run() {
try {
Thread.sleep(17);
} catch (InterruptedException e) {
e.printStackTrace();
}
Platform.runLater(new Runnable() {
#Override
public void run() {
System.out.println(getNodeBorderCoords(bp, BorderTypes.RIGHT)[0]);
System.out.println(getNodeBorderCoords(bp, BorderTypes.RIGHT)[1]);
}
});
}
});
t.start();
But delaying the call might cause some strange behaviour like i stated in my post. But i found another "solution" recently.
bp.snapshot(new SnapshotParameters(), new WritableImage(5, 5));
System.out.println(getNodeBorderCoords(bp, BorderTypes.RIGHT)[0]);
System.out.println(getNodeBorderCoords(bp, BorderTypes.RIGHT)[1]);
The snapshot() method applies all css effects (and all other layout work) on the node. After that, the returned values of the borders are correct.

Answer 1

There are 2 approaches:
You can use binding instead of static size call. It gives benefits of additional support for update after resize but adds a bit of listeners handling burden on FX enging.
Wrapping size reading logic into Platform.runLater() will put it later into event queue and should address premature size access issue.