sbool mouseEventIsInBorder(MouseEvent e) swing {
  var c = optCast JComponent(e.getComponent());
  if (c == null) false;
  var border = c.getBorder(c);
  if (border == null) false;
  Insets insets = border.getBorderInsets(c);
  ret e.getX() < insets.left
    || e.getX() >= c.getWidth()-insets.right
    || e.getY() < insets.top
    || e.getY() >= c.getHeight()-insets.bottom;
}