anchor.diff:  procedure TKMListHeader.DoClick(X,Y: Integer; Shift: TShiftState; Button: TMouseButton);
   var ColumnID: Integer;
   begin
  +  //do not invoke inherited here, to fully override parent DoClick method
     ColumnID := GetColumnIndex(X);
     if (ColumnID <> -1) and Assigned(OnColumnClick) then
     begin
  
positive.code:     function GetTop: Integer;
      function GetHeight: Integer;
      function GetWidth: Integer;
  
      function GetVisible: Boolean;
      procedure SetAbsLeft(aValue: Integer);
  
negative.code:     procedure ControlMouseDown(Sender: TObject; Shift: TShiftState); virtual;
      procedure ControlMouseUp(Sender: TObject; Shift: TShiftState); virtual;
      procedure FocusChanged(aFocused: Boolean); virtual;
    public
      Hitable: Boolean; //Can this control be hit with the cursor?
      Focusable: Boolean; //Can this control have focus (e.g. TKMEdit sets this true)
  