def hook_newHeadline(VO, level, blnum, tlnum):
    """Return (tree_head, bodyLines).
    tree_head is new headline string in Tree buffer (text after |).
    bodyLines is list of lines to insert in Body buffer.
    """
    tree_head = 'NewHeadline'
    # choose = or + headline type -- same as previous headline
    if tlnum > 1:
        prev_head = VO.Body[VO.bnodes[tlnum-1] - 1]
        if prev_head.lstrip()[0] == '=':
            lev = '='*level
        else:
            lev = '+'*level
    else:
        lev = '='*level
    bodyLines = ['%s NewHeadline %s' %(lev, lev), '']
    return (tree_head, bodyLines)