Dragging window around

Question

Hi, I'm trying to drag around the main scene for the program, the stage is undecorated, so no border.
I'm basically using:
scene.getWindow().setX(across);
scene.getWindow().setY(down);
And this works fine, but also, I have a background (An ImageView added to the scene, that I would like to update as the window us moved).
The background is basically a screenshot of the desktop (I'm using this instead of null fill on the stage, since a transparent stage give choppy results).
So next I do...
setViewport(rect);
Where Rectangle2D rect = new Rectangle2D(across, down, s, s);
This works "okay", but when dragging the stage, its usually out of sync,
As if it can't update the viewport in time with the motion of the window across the screen.
I've tried using threads, and platform.runLater, but I can't really get it to work without going out of sync.
Any ideas, thanks.

Answer 1

It's hard to imagine the overhead of manipulating and drawing the background image is going to make things less "choppy" than using a transparent stage. If the aim is simply to have a draggable window where the user can see the desktop in the background, a transparent stage is the way to go. The following test runs fine on my system:
import javafx.application.Application;
import javafx.beans.property.ObjectProperty;
import javafx.beans.property.SimpleObjectProperty;
import javafx.event.ActionEvent;
import javafx.event.EventHandler;
import javafx.geometry.Point2D;
import javafx.scene.Scene;
import javafx.scene.control.Button;
import javafx.scene.input.MouseEvent;
import javafx.scene.layout.StackPane;
import javafx.scene.paint.Color;
import javafx.stage.Stage;
import javafx.stage.StageStyle;
public class TransparentWindowDragTest extends Application {
    @Override
    public void start(final Stage primaryStage) {
        primaryStage.initStyle(StageStyle.TRANSPARENT);
        final StackPane root = new StackPane();
        root.setStyle("-fx-border-color: blue;");
        final Button button = new Button("Close");
        button.setOnAction(new EventHandler<ActionEvent>() {
            @Override
            public void handle(ActionEvent event) {
                primaryStage.hide();
        root.getChildren().addAll(button);
        final Scene scene = new Scene(root, 300, 200, Color.TRANSPARENT);
        final ObjectProperty<Point2D> mouseOffset = new SimpleObjectProperty<>();
        scene.setOnMousePressed(new EventHandler<MouseEvent>() {
            @Override
            public void handle(MouseEvent event) {
                mouseOffset.set(new Point2D(
                    event.getScreenX() - primaryStage.getX(),
                    event.getScreenY() - primaryStage.getY()
        scene.setOnMouseDragged(new EventHandler<MouseEvent>() {
            @Override
            public void handle(MouseEvent event) {
                primaryStage.setX(event.getScreenX() - mouseOffset.get().getX());
                primaryStage.setY(event.getScreenY() - mouseOffset.get().getY());
        primaryStage.setScene(scene);
        primaryStage.show();
    public static void main(String[] args) {
        launch(args);