During the FormShow event, send the combo box a CB_SHOWDROPDOWN message twice, once to drop it down, and once to retract it. Then send a CB_GETDROPPEDCONTROLRECT message, passing the address of a TRect. When the SendMessage call returns, the TRect will contain the rectangle that would enclose the ComboBox in it's dropped down state, relative to the screen. You can then call ScreenToClient to convert the TRect's coordinates to be relative to the client area of the form.

Example:

var R : TRect;

procedure TForm .FormShow(Sender: TObject); var T : TPoint; begin SendMessage(ComboBox .Handle, CB_SHOWDROPDOWN, , 0); SendMessage(ComboBox .Handle, CB_SHOWDROPDOWN, 0, 0); SendMessage(ComboBox .Handle, CB_GETDROPPEDCONTROLRECT, 0, LongInt(@r)); t := ScreenToClient(Point(r.Left, r.Top)); r.Left := t.x; r.Top := t.y; t := ScreenToClient(Point(r.Right, r.Bottom)); r.Right := t.x; r.Bottom := t.y; end;

procedure TForm .Button Click(Sender: TObject); begin Form .Canvas.Rectangle(r.Left, r.Top, r.Right, r.Bottom ); end; 7/ 6/98 4:3 :28 PM