Author: Jonas Bilinkevicius

How to give a listbox a rounded border

Answer:

To round a ListBox use CreateRoundRectRgn to shape it. Reduce the client size to 
reposition back in place. Experiment with the rounding value. The greater the round 
value the smoother it is.

Add a TListBox to a form

1   procedure TForm1.RoundListbox(var TheList: TListbox);
2   const
3     schange = 5;
4     rnd = 20;
5   var
6     thergn: HRGN;
7     mclient: TRect;
8   begin
9     mclient := TheList.ClientRect; {get size}
10    thergn := CreateRoundRectRgn(mclient.Left, mclient.top, mclient.right,
11      mclient.bottom, rnd, rnd);
12    TheList.BorderStyle := bsNone;
13    InflateRect(mclient, -schange, -schange); {shrink}
14    TheList.Perform(EM_SETRECTNP, 0, lparam(@mclient)); {change}
15    SetWindowRgn(TheList.Handle, thergn, true);
16  end;