JavaFX: animation which uses PathTransition as a drawing pen - animation

Question

sample code
//node
Rectangle rect = new Rectangle (0, 0, 20, 20);
//path
Text text = TextBuilder.create()
.text("J a v a F X R o c k s")
.font(new Font(50))
.x(65)
.y(100)
.build();
// path transition
pathTransition = PathTransitionBuilder.create()
.duration(Duration.seconds(15))
.path(text)
.node(rect)
.orientation(OrientationType.ORTHOGONAL_TO_TANGENT)
.cycleCount(Timeline.INDEFINITE)
.autoReverse(true)
.build();
I want to display part of the the text(path) that traveled by rect node. Meaning in the above figure as rect node traveled until java, i want to be display that part only at that point of time ..

Answer 1

You can try to assign a clipping area to the Text and update it during animation:
public void start(Stage primaryStage) {
final Rectangle pen = new Rectangle(0, 0, 20, 20);
// this pane this contain clipping
final Pane clip = new Pane();
// listener to update clipping area
ChangeListener changeListener = new ChangeListener() {
#Override
public void changed(ObservableValue ov, Object t, Object t1) {
Rectangle newrect = new Rectangle(pen.getTranslateX(), pen.getTranslateY(), pen.getWidth(), pen.getHeight());
newrect.setRotate(pen.getRotate());
clip.getChildren().add(newrect);
}
};
// rect coordinates will be changed during animation, so we will listen to them
pen.translateXProperty().addListener(changeListener);
pen.translateYProperty().addListener(changeListener);
pen.rotateProperty().addListener(changeListener);
final Text text = TextBuilder.create()
.text("J a v a F X R o c k s")
.font(new Font(50))
.clip(clip)
.x(65)
.y(100)
.build();
PathTransition pathTransition = PathTransitionBuilder.create()
.duration(Duration.seconds(15))
.path(text)
.node(pen)
.orientation(OrientationType.ORTHOGONAL_TO_TANGENT)
.build();
// once we done we don't want to store thousands of rectangles used to clip
pathTransition.setOnFinished(new EventHandler<ActionEvent>() {
#Override
public void handle(ActionEvent t) {
text.setClip(null);
clip.getChildren().clear();
}
});
Pane root = new Pane();
root.getChildren().addAll(text, pen);
primaryStage.setScene(new Scene(root, 600, 200));
primaryStage.show();
pathTransition.play();
}
A bit more efficient way to store clipping area can be Canvas object, but it will require a bit of math to draw rectangles with rotation on canvas, so it's your call.