Generic Printer & Winspool & Delphi

[Averwind]

I am trying to print line by line on a thermal printer using Windows generic printer drivers. The code I use to print a line is presented below. The code works OK. But the problem is the application freezes when there is a print operation. Is there something I am doing wrong? Should I use something else other than Winspool?

Procedure PrintLineToGeneric(Const line: string );
var
  BytesWritten: DWORD;
  DocInfo: TDocInfo1;
Begin
  if WinSpool.OpenPrinter(PChar(printerName), hPrinter, nil) Then
    //raise exception.create('Printer not found');
  Try
    DocInfo.pDocName := 'MyDocument';
    DocInfo.pOutputFile := Nil;
    DocInfo.pDatatype := 'RAW';
    If StartDocPrinter(hPrinter, 1, @DocInfo) = 0 Then
      Abort;

    Try
      StartPagePrinter(hPrinter);
      If not StartPagePrinter(hPrinter) Then
        Abort;
      try
        If not WritePrinter(hPrinter, @line[1], Length(line), BytesWritten)
        Then
          Abort;
      Finally
        EndPagePrinter(hPrinter);
      End;
    Finally
      EndDocPrinter(hPrinter);
    End;
  Finally
    WinSpool.ClosePrinter(hPrinter);
  End;
End;