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Impressão direto pra porta (lpt, usb)

Código

//declare o tipo e a classe abaixo

//caso alguem tenha alguma duvida entre em contato

//ntw@wmail.com.br

type

  DOC_INFO_1 = Packed Record

    pDocName: PChar;

    pOutputFile: PChar;

    pDataType: PChar;

  End;

  TDirectPrinterStream = Class(TStream)

  private

    FPrinter: TPrinter;

    FHandle: THandle;

    FTitle: String;

    procedure CreateHandle;

    procedure FreeHandle;

  public

    constructor Create(aPrinter: TPrinter; aTitle: String);

    destructor Destroy; Override;

    function Write(const Buffer; Count: LongInt): Longint; Override;

    function Read(var Buffer; Count: Longint): Longint; override;

    property Handle: THandle Read FHandle;

  End;

//a implementação e a seguinte:

{********************** STREAM DE DADOS PARA A IMPRESSAO DIRETO PRA IMPRESSORA}

Constructor TDirectPrinterStream.Create(aPrinter: TPrinter; aTitle: String);

Begin

  Inherited Create;

  FPrinter := aPrinter;

  FTitle := aTitle;

  CreateHandle;

End;

procedure TDirectPrinterStream.CreateHandle;

var

  DocInfo: DOC_INFO_1;

  aDevice, aDriver, aPort: Array[0..255] Of Char;

  aMode: Cardinal;

Begin

  FreeHandle;

  if FHandle = 0 then

    begin

      FPrinter.GetPrinter(aDevice, aDriver, aPort, aMode);

      if OpenPrinter(aDevice, FHandle, Nil) then

        begin

          DocInfo.pOutputFile:=nil;

          DocInfo.pDataType:='RAW';

          DocInfo.pDocName := PChar(FTitle);

          if StartDocPrinter(FHandle, 1, @DocInfo) = 0 then

            begin

              ClosePrinter(FHandle);

              FHandle := 0;

            end

          else if not StartPagePrinter(FHandle) then

            begin

              EndDocPrinter(FHandle);

              ClosePrinter(FHandle);

              FHandle := 0;

            end;

        end;

    end;

End;

destructor TDirectPrinterStream.Destroy;

begin

  FreeHandle;

  inherited;

end;

procedure TDirectPrinterStream.FreeHandle;

begin

  if FHandle <> 0 then

    begin

      EndPagePrinter(FHandle);

      EndDocPrinter(FHandle);

      ClosePrinter(FHandle);

      FHandle := 0;

    end;

End;

function TDirectPrinterStream.Read(var Buffer; Count: Integer): Longint;

begin

  inherited;

  Result:=0;

end;

function TDirectPrinterStream.Write(const Buffer; Count: LongInt): Longint;

var Bytes: Cardinal;

begin

  WritePrinter(Handle, @Buffer, Count, Bytes);

  Result := Bytes;

End;

//exemplo de uso:

procedure PrintDoc(sNomDoc: String = ''; sNomeArq: String = '');

var Impressora: TDirectPrinterStream;

    MemTxt: TMemoryStream;

begin

  Impressora := TDirectPrinterStream.Create(Printer, sNomDoc);

  try

    MemTxt:=TMemoryStream.Create();//criacao dos streams para a copia dos dados

    FStrTXT.SaveToStream(MemTxt);//descarrega os dados gravados em memoria no stream

    try

      Impressora.CopyFrom(MemTxt, 0);//inicia o processo de copia dos dados para a instancia aberta da impressora

    finally

      MemTxt.Free;

    end;

  finally

    Impressora.Free;

    FStrTXT.Free;

  end;

end;