procedure TDemoForm.CreatePanels(n, cols, gap: Integer; pc: TScrollBox);
var
  i, rows, pnlWidth, pnlHeight, vsbWidth: Integer;
begin
  if n > 4
    then vsbWidth := GetSystemMetrics(SM_CXVScroll)
    else vsbWidth := 0;
  pnlWidth := Round((pc.ClientWidth - vsbWidth - Succ(cols) * gap) div cols);
  pnlHeight := Round((pc.Height - Succ(cols) * gap) div cols);
  Panels.Clear;
  rows := Succ(n) div cols;
  pc.VertScrollBar.Range := gap + rows * (gap + pnlHeight) - 4;
  while Panels.Count < n do
    with TPanel(Panels[Panels.Add(TPanel.Create(self))]) do
    begin
      i := Pred(Panels.Count);
      Parent := pc;
      Caption := Format('Panel %d', [Succ(i)]);
      Width := pnlWidth;
      Height := pnlHeight;
      Left := gap + (i mod cols) * (gap + Width);
      Top := gap + (i div cols) * (gap + Height);
    end;
end;