void tabControl_MouseMove(object sender, MouseEventArgs e)
{
int tabIdx = TestTab( new Point( e.X, e.Y ) );
if (tabIdx != -1 && _lastTab != tabIdx)
{
_lastTab = tabIdx;
ToolTip.SetToolTip( tabPanelControl, tabPanelControl.TabPages[tabIdx].ToolTipText );
}
}