ADDITIONAL SYSTEM INFORMATION :
Ubuntu 20.04.6 LTS
JavaFX 20
OpenJDK 22.0.1+8-16

A DESCRIPTION OF THE PROBLEM :
Run the provided code. You will see that on changing transparent stage Y position and height the bottom side is shaking, see <link> The same problem with the right side while changing X position and width. Besides, you will see the same problem if you use undecorated stage.

It is not possible to test the provided code in javafx 21-24 because of the JDK-8344372 .

Because of this bug it is not possible to use a custom stage in JavaFX as the bug doesn't let to implement the window resizing using top/left border. Similar to JDK-8344372, this bug prevents performing the most basic operations with Stage.

STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
Run the code. Click on the stage and move mouse up and bottom.


---------- BEGIN SOURCE ----------
public class NewMain extends Application {

    public static void main(String args[]){
        launch(args);
    }

    private Stage stage;

    private double initialY;

    private double initialHeight;

    private double initialMouseY;

    @Override
    public void start(Stage stage) throws Exception {
        this.stage = stage;
        var root = new VBox();
        root.setStyle("-fx-background-color: yellow");
        root.setOnMousePressed(e -> onMousePressed(e));
        root.setOnMouseDragged(e -> onMouseDragged(e));
        var scene = new Scene(root, 600, 400);
        stage.initStyle(StageStyle.TRANSPARENT);
        stage.setScene(scene);
        stage.show();
    }

    private void onMousePressed(MouseEvent e) {
        this.initialY = stage.getY();
        this.initialHeight = stage.getHeight();
        this.initialMouseY = e.getScreenY();
    }

    private void onMouseDragged(MouseEvent e) {
        var d = this.initialMouseY - e.getScreenY();
        stage.setHeight(this.initialHeight + d);
        stage.setY(this.initialY - d);
    }
}
---------- END SOURCE ----------