{ Scroll Bar notifications }
      SB_LINEUP = 0;
      SB_LINEDOWN = 1;
      SB_LINELEFT = 0;
      SB_LINERIGHT = 1;
      SB_PAGEUP = 2;
      SB_PAGEDOWN = 3;
      SB_PAGELEFT = 2;
      SB_PAGERIGHT = 3;
      SB_THUMBPOSITION = 4;
      SB_THUMBTRACK = 5;
      SB_ENDSCROLL = 8;
      SB_LEFT = 6;
      SB_RIGHT = 7;
      SB_BOTTOM = 7;
      SB_TOP = 6;