Give a listbox a rounded border

Problem/Question/Abstract:

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

procedure TForm1.RoundListbox(var TheList: TListbox);
const
schange = 5;
rnd = 20;
var
thergn: HRGN;
mclient: TRect;
begin
mclient := TheList.ClientRect; {get size}
thergn := CreateRoundRectRgn(mclient.Left, mclient.top, mclient.right,
mclient.bottom, rnd, rnd);
TheList.BorderStyle := bsNone;
InflateRect(mclient, -schange, -schange); {shrink}
TheList.Perform(EM_SETRECTNP, 0, lparam(@mclient)); {change}
SetWindowRgn(TheList.Handle, thergn, true);
end;