Swing/ToolBarButtonToolTipOrientation のバックアップ(No.1)

private Component createToolBarButton(ColorItem item) {
  JButton button = new JButton(item.getIcon()) {
    private transient BalloonToolTip tip;
    private final JLabel label = new JLabel(" ", CENTER);

    @Override public Point getToolTipLocation(MouseEvent e) {
      String txt = getToolTipText();
      return Optional.ofNullable(txt).map(toolTipText -> {
        JToolTip tips = createToolTip();
        tips.setTipText(toolTipText);
        label.setText(toolTipText);
        Container bar = SwingUtilities.getAncestorOfClass(JToolBar.class, this);
        String constraint = calculateConstraint(bar.getParent(), bar);
        if (tips instanceof BalloonToolTip) {
          ((BalloonToolTip) tips).updateBalloonShape(constraint);
        }
        return getToolTipPoint(getPreferredSize(), tips.getPreferredSize(), constraint);
      }).orElse(null);
    }

    @Override public JToolTip createToolTip() {
      if (tip == null) {
        tip = new BalloonToolTip();
        LookAndFeel.installColorsAndFont(
            label, "ToolTip.background", "ToolTip.foreground", "ToolTip.font");
        tip.add(label);
        Container bar = SwingUtilities.getAncestorOfClass(JToolBar.class, this);
        String constraint = calculateConstraint(bar.getParent(), bar);
        tip.updateBalloonShape(constraint);
        tip.setComponent(this);
      }
      return tip;
    }

    @Override public void updateUI() {
      tip = null;
      super.updateUI();
    }
  };
  button.setOpaque(false);
  button.setToolTipText(item.getTitle());
  button.setFocusPainted(false);
  return button;
}

private static String calculateConstraint(Container source, Component toolBar) {
  String constraint = null;
  JToolBar bar = (JToolBar) toolBar;
  if (((BasicToolBarUI) bar.getUI()).isFloating()) {
    if (bar.getOrientation() == SwingConstants.VERTICAL) {
      boolean leftToRight = bar.getComponentOrientation().isLeftToRight();
      constraint = leftToRight ? BorderLayout.WEST : BorderLayout.EAST;
    }
  } else {
    LayoutManager lm = source.getLayout();
    if (lm instanceof BorderLayout) {
      constraint = (String) ((BorderLayout) lm).getConstraints(toolBar);
    }
  }
  return constraint == null ? BorderLayout.NORTH : constraint;
}

private static Point getToolTipPoint(Dimension btnSz, Dimension tipSz, String constraint) {
  double dx;
  double dy;
  switch (constraint) {
    case BorderLayout.WEST:
      dx = btnSz.getWidth();
      dy = (btnSz.getHeight() - tipSz.getHeight()) / 2d;
      break;
    case BorderLayout.EAST:
      dx = -tipSz.getWidth();
      dy = (btnSz.getHeight() - tipSz.getHeight()) / 2d;
      break;
    case BorderLayout.SOUTH:
      dx = (btnSz.getWidth() - tipSz.getWidth()) / 2d;
      dy = -tipSz.getHeight();
      break;
    default: // case BorderLayout.NORTH:
      dx = (btnSz.getWidth() - tipSz.getWidth()) / 2d;
      dy = btnSz.getHeight();
  }
  return new Point((int) (dx + .5), (int) (dy + .5));
}