Swing/DnDTabbedPane のバックアップ(No.23)

private int getTargetTabIndex(Point glassPt) {
  Point tabPt = SwingUtilities.convertPoint(glassPane, glassPt, DnDTabbedPane.this);
  boolean isTB = getTabPlacement() == JTabbedPane.TOP || getTabPlacement() == JTabbedPane.BOTTOM;
  for (int i = 0; i < getTabCount(); i++) {
    Rectangle r = getBoundsAt(i);
    if (isTB) r.setRect(r.x - r.width / 2, r.y, r.width, r.height);
    else      r.setRect(r.x, r.y-r.height / 2, r.width, r.height);
    if (r.contains(tabPt)) return i;
  }
  Rectangle r = getBoundsAt(getTabCount() - 1);
  if (isTB) r.setRect(r.x + r.width / 2, r.y, r.width, r.height);
  else      r.setRect(r.x, r.y + r.height / 2, r.width, r.height);
  return    r.contains(tabPt) ? getTabCount() : -1;
}

private void convertTab(int prev, int next) {
  if (next < 0 || prev == next) {
    return;
  }
  Component cmp = getComponentAt(prev);
  Component tab = getTabComponentAt(prev);
  String str    = getTitleAt(prev);
  Icon icon     = getIconAt(prev);
  String tip    = getToolTipTextAt(prev);
  boolean flg   = isEnabledAt(prev);
  int tgtindex  = prev > next ? next : next - 1;
  remove(prev);
  insertTab(str, icon, cmp, tip, tgtindex);
  setEnabledAt(tgtindex, flg);

  //When you drag'n'drop a disabled tab, it finishes enabled and selected.
  //pointed out by dlorde
  if (flg) setSelectedIndex(tgtindex);

  // I have a component in all tabs (jlabel with an X to close the tab)
  // and when i move a tab the component disappear.
  // pointed out by Daniel Dario Morales Salas
  setTabComponentAt(tgtindex, tab);
}