@Override
            public void mouseDragged(MouseEvent event) {
                double zoomLevel = grammarWindow.getZoomLevel();
                int dx = (int) Math.round((1.0d * (event.getX() - mouseClickPoint.x) / zoomLevel) + mouseDragTransformation.x);
                int dy = (int) Math.round((1.0d * (event.getY() - mouseClickPoint.y) / zoomLevel) + mouseDragTransformation.y);
                mouseDragTransformation.setLocation(dx, dy);
                mouseClickPoint = event.getPoint();
                repaint();
            }