anchor.diff:  procedure TfpgListBoxStrings.Delete(Index: Integer);
   begin
     inherited Delete(Index);
  +  if UpdateCount > 0 then
  +      Exit;
     if Assigned(ListBox) and (ListBox.HasHandle) then
     begin
       ListBox.UpdateScrollBar;
  
positive.code:   TfpgListBoxStrings = class(TStringList)
    protected
      ListBox: TfpgTextListBox;
      procedure   SetUpdateState(Updating: Boolean); override;
    public
      constructor Create(AListBox: TfpgTextListBox);
      destructor  Destroy; override;
  
negative.code: 
  { TfpgListBoxStrings }
  
  constructor TfpgListBoxStrings.Create(AListBox: TfpgTextListBox);
  begin
    inherited Create;
  