JTabbedPaneのタブが配置されたランの位置を取得する

JTabbedPane tabs = new JTabbedPane() {
  @Override public void addTab(String title, Icon icon, Component component) {
    super.addTab(title, icon, component, title);
  }

  @Override public String getToolTipText(MouseEvent e) {
    String tip = super.getToolTipText(e);
    int idx = indexAtLocation(e.getX(), e.getY());
    if (idx >= 0 && isHorizontalTabPlacement()) {
      int run = getRunForTab(getTabCount(), idx);
      tip = String.format("%s: Run: %d", tip, run);
    }
    return tip;
  }

  private int getRunForTab(int tabCount, int tabIndex) {
    int runCount = getTabRunCount();
    Rectangle taRect = getTabAreaRect(tabCount);
    int runHeight = taRect.height / runCount;
    Rectangle tabRect = getBoundsAt(tabIndex);
    Point2D pt = new Point2D.Double(
        tabRect.getCenterX(), tabRect.getCenterY());
    Rectangle runRect = new Rectangle(
        taRect.x, taRect.y, taRect.width, runHeight);
    int run = -1;
    for (int i = 0; i < runCount; i++) {
      if (runRect.contains(pt)) {
        run = i;
      }
      runRect.translate(0, runHeight);
    }
    return getTabPlacement() == TOP ? runCount - run - 1 : run;
  }

  private Rectangle getTabAreaRect(int tabCount) {
    Rectangle rect = getBoundsAt(0);
    for (int i = 0; i < tabCount; i++) {
      rect.add(getBoundsAt(i));
    }
    return rect;
  }

  private boolean isHorizontalTabPlacement() {
    return getTabPlacement() == TOP || getTabPlacement() == BOTTOM;
  }
};