怎样设置双面打印？

Question

给你一段打印机初始化的代码，双面打印具体应该设哪个属性，还要试试，反正思路应该是这样：
注意先引用Printers单元。
procedure TForm1.Button1Click(Sender: TObject);
var
  ADevice, ADriver, APort: array[0..255] of Char;
  DeviceHandle: THandle;
  DevMode: PDeviceMode;
begin
    //初始化打印机
    Printer.GetPrinter(ADevice, ADriver, APort, DeviceHandle);
    if DeviceHandle = 0 then
    begin
      Printer.PrinterIndex := Printer.PrinterIndex;
      Printer.GetPrinter(ADevice, ADriver, APort, DeviceHandle);
    end;
    if DeviceHandle = 0 then
      Raise Exception.Create('不能初始化打印机！')
    else
      DevMode := GlobalLock(DeviceHandle);
    if DeviceHandle <> 0 then
    begin
      with DevMode^ do
      begin
        dmFields := dmFields or DM_ORIENTATION;
        //在下面这里设置打印方向
        dmOrientation := DMORIENT_LANDSCAPE; //DMORIENT_PORTRAIT
        Printer.SetPrinter(ADevice, ADriver, APort, DeviceHandle);
        GlobalUnLock(DeviceHandle);
      end;
    end;    PrinterSetupDialog1.Execute; //验证一下设置是否成功了
end;