canvas.setOnMousePressed(new EventHandler<MouseEvent>(){

            @Override
            public void handle(MouseEvent event) {
                if (event.getClickCount() > 1) {
                    drawing = false;
                }
                gc.beginPath();
                gc.moveTo(event.getX(), event.getY());
                gc.stroke();
            }
        });
        canvas.setOnMouseDragged(new EventHandler<MouseEvent>() {

            @Override
            public void handle(MouseEvent event) {
                if(drawing) {
                    gc.lineTo(event.getX(), event.getY());
                    gc.stroke();
                } else {
                    gc.fillOval(event.getX(), event.getY(), 10, 10);
                }
            }

        });