Detect the status of a printer paper

i need to get paper status information from a printer. I have a list of esc/pos commands. I'm trying to send these comands with escape function

http://msdn.microsoft.com/en-us/library/windows/desktop/dd162701%28v=vs.85%29.aspx

This is my code

type
TPrnBuffRec = record
  bufflength: Word;
  Buff_1: array[0..255] of Char;
end;

procedure TFTestStampa.SpeedButton2Click(Sender: TObject);
var
  Buff: TPrnBuffRec;
  BuffOut: TPrnBuffRec;
  TestInt: Integer;
  cmd : string;
begin
  printer.BeginDoc;

  try
    TestInt := PassThrough;
    if Escape(Printer.Handle, QUERYESCSUPPORT, SizeOf(TESTINT),
@testint, nil) > 0 then
      begin
        cmd := chr(10) + chr(04) + '4';
        StrPCopy(Buff.Buff_1, cmd);
        Buff.bufflength := StrLen(Buff.Buff_1);
        Escape(Printer.Canvas.Handle, Passthrough, 0, @buff,
@buffOut);

        ShowMessage( conver(strPas(buffOut.Buff_1)) );
      end

  finally
    printer.EndDoc;

end;


function TFTestStampa.Conver(s: string): String;
var
  i:  Byte;
  t : String;
begin
  t := '';
  for i := 1 to Length(s)  do
    t := t + IntToHex(Ord(s[i]), 2) + ' ';
  Result := t;
end; 

开发者_如何转开发Problem is with different cmds I obtain always the same string .... Can you give me an example of escape function with last parameter not nill ? Alternatives to obtain paper status ?

I suppose you are using Delphi 2009 above and you used this source for your example, so your problem might be caused by Unicode parameters. In Delphi since version 2009, string type is defined as UnicodeString whilst in Delphi 2009 below as AnsiString, the same stands also for Char which is WideChar in Delphi 2009 up and AnsiChar below.

If so, then I think you have a problem at least with your buffer data length, because Char = WideChar takes 2 bytes and you were using StrLen function which returns the number of chars what cannot correspond to the data size of number of chars * 2 bytes.

I hope this will fix your problem, but I can't verify it, because I don't have your printer :)

type
  TPrinterData = record
    DataLength: Word;
    Data: array [0..255] of AnsiChar; // let's use 1 byte long AnsiChar
end;

function Convert(const S: AnsiString): string;
var
  I: Integer; // 32-bit integer is more efficient than 8-bit byte type
  T: string;  // here we keep the native string data type
begin
  T := '';
  for I := 1 to Length(S) do
    T := T + IntToHex(Ord(S[I]), 2) + ' ';
  Result := T;
end;

procedure TFTestStampa.SpeedButton2Click(Sender: TObject);
var
  TestInt: Integer;
  Command: AnsiString;
  BufferIn: TPrinterData;
  BufferOut: TPrinterData;
begin
  Printer.BeginDoc;

  try
    TestInt := PASSTHROUGH;

    if Escape(Printer.Handle, QUERYESCSUPPORT, SizeOf(TestInt), @TestInt, nil) > 0 then
    begin
      Command := Chr(10) + Chr(04) + '4';
      StrPCopy(BufferIn.Data, Command);
      BufferIn.DataLength := StrLen(Command);
      FillChar(BufferOut.Data, Length(BufferOut.Data), #0);
      BufferOut.DataLength := 0;
      Escape(Printer.Canvas.Handle, PASSTHROUGH, 0, @BufferIn, @BufferOut);

      ShowMessage(Convert(StrPas(BufferOut.Data)));
    end

  finally
    Printer.EndDoc;
  end;
end;