Swing/DnDTabbedPane のバックアップ(No.21)

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);
}