COMCOBOX下拉水平宽度

use CB_SETDROPPEDWIDTH
Like:
procedrue Tform1.FormShow(Sender : Tobjects)
begin
comboBox1.Perform(CB_SETDROPPEDWIDTH, 100, 0);
end;
procedure TForm1.ComboBox1DropDown(Sender: TObject);
var
I: Integer;
vMaxWidth: Integer;
begin
vMaxWidth := TComboBox(Sender).Width;
for I := 0 to TComboBox(Sender).Items.Count - 1 do
vMaxWidth := Max(vMaxWidth,
TComboBox(Sender).Canvas.TextWidth(TComboBox(Sender).Items) + 8);
TComboBox(Sender).Perform(CB_SETDROPPEDWIDTH, vMaxWidth, 0);
end;