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c++winapiprintingpdf-generationpostscript

PDF printer generates PDF only when output file name is not set

The following code snippet sends PostScript content (saved in pBuf buffer) to a CutePDF printer:

if (OpenPrinter(printerName, &hPrinter, NULL))
{
  DOC_INFO_1 di1;
  di1.pDatatype = L"RAW";
  di1.pDocName = L"Raw print document";
  di1.pOutputFile = NULL;
  StartDocPrinter(hPrinter, 1, (LPBYTE)&di1);
  StartPagePrinter(hPrinter);   
  DWORD dwWritten = 0;
  WritePrinter(hPrinter, pBuf, dwBufSize, &dwWritten);
  EndPagePrinter(hPrinter);
  EndDocPrinter(hPrinter);
}

During the execution of this code, a dialog appears where I specify the name of the output file (e.g. D:/out.pdf), after that the pdf file is generated. So far so good. The problems begin when I'm trying to avoid the filename specifying step by changing Line 4 of the snippet:

di1.pOutputFile = L"D:/out.pdf";

Such code doesn't show the dialog during its execution (as expected), but the result D:/out.pdf isn't a pdf file, it's a copy of the PostScript file sent to the printer (copy of the contents of pBuf buffer). PDF Writer behaves in the same way. Why do PDF printers behave in this way and how can I achieve the needed behaviour (generate PDF file without specifying its name in UI)?

Solution

  • The Windows print system behaves this way, because, to be blunt, that's how its supposed to behave. If you specify a filename at that point then the print system sends the output to that file. If you don't specify a filename then it proceeds to normal processing.

    Normally you would send the printer driver output to a port, and in the case of PDF printers a custom port monitor would pick up the output (PostScript in this case) and process it further. For PDF printers they send the PostScript on to a process which converts the PostScript to PDF (almost always using Ghostscript, though the Adobe print to PDF tools work the same way).

    If you want to alter the output of the PDF process (ie write it to a different file), then you need to alter the way the port monitor works, not the way the print subsystem works, which is what your code is currently doing. By setting a filename where you are, you are simply short-circuiting the process, never invoking the port monitor, which is why the 'save file' dialog does not appear, and why the output is PostScript.

    There may be a way of specifying the output file documented for the specific PDF printer you are using. If not, then for open source products (and if GS is built in they should be GPL licensed) you can request a copy of the source code for the product and alter it to suit yourself.

    Alternatively, you can pick up a copy of Ghostscript and RedMon (open source Port Monitor) and create your own tool for doing the same job.