How to programmatically print to a non-default printer in MFC

MORE INFORMATION

During a normal print operation in an MFC application, the print dialog box is displayed which allows you to select the printer you want to print to. The default printer displayed in the print dialog box is the default printer specified in the operating system. MFC stores the default printer of the application in the CWinApp::m_hDevMode and CWinApp::m_hDevNames protected data members. Because MFC initializes these variables to NULL, the MFC print architecture defaults to the operating system's default printer the first time a print operation is performed. The operating system default printer's DEVMODE and DEVNAMES are then copied to the MFC application's m_hDevMode and m_hDevNames data members.

Occasionally, there may be a situation where you need to print to a printer other than the default printer without having the user specify it through the print dialog box. The non-default printer can be a secondary printer or a network printer (assuming your operating system has the drivers already installed).

Whether you need to use the non-default printer on a permanent basis or for only one print job, you need the DEVMODE and DEVNAMES structure to create the printer DC. The PRINTER_INFO_2 structure from GetPrinter() contains all the information needed to fill the DEVMODE and DEVNAMES structures.

Creating a DEVMODE and DEVNAMES Structure

The sample code below shows how to use GetPrinter() to create a DEVMODE and DEVNAMES structure based on a printer name. The code is a global function which returns the data structures through its parameters.

#include <winspool.h>

// returns a DEVMODE and DEVNAMES for the printer name specified
BOOL GetPrinterDevice(LPTSTR pszPrinterName, HGLOBAL* phDevNames, HGLOBAL* phDevMode)
{
    // if NULL is passed, then assume we are setting app object's
    // devmode and devnames
    if (phDevMode == NULL || phDevNames == NULL)
        return FALSE;

    // Open printer
    HANDLE hPrinter;
    if (OpenPrinter(pszPrinterName, &hPrinter, NULL) == FALSE)
        return FALSE;

    // obtain PRINTER_INFO_2 structure and close printer
    DWORD dwBytesReturned, dwBytesNeeded;
    GetPrinter(hPrinter, 2, NULL, 0, &dwBytesNeeded);
    PRINTER_INFO_2* p2 = (PRINTER_INFO_2*)GlobalAlloc(GPTR,
        dwBytesNeeded);
    if (GetPrinter(hPrinter, 2, (LPBYTE)p2, dwBytesNeeded,
       &dwBytesReturned) == 0) {
       GlobalFree(p2);
       ClosePrinter(hPrinter);
       return FALSE;
    }
    ClosePrinter(hPrinter);

    // Allocate a global handle for DEVMODE
    HGLOBAL  hDevMode = GlobalAlloc(GHND, sizeof(*p2->pDevMode) +
       p2->pDevMode->dmDriverExtra);
    ASSERT(hDevMode);
    DEVMODE* pDevMode = (DEVMODE*)GlobalLock(hDevMode);
    ASSERT(pDevMode);

    // copy DEVMODE data from PRINTER_INFO_2::pDevMode
    memcpy(pDevMode, p2->pDevMode, sizeof(*p2->pDevMode) +
       p2->pDevMode->dmDriverExtra);
    GlobalUnlock(hDevMode);

    // Compute size of DEVNAMES structure from PRINTER_INFO_2's data
    DWORD drvNameLen = lstrlen(p2->pDriverName)+1;  // driver name
    DWORD ptrNameLen = lstrlen(p2->pPrinterName)+1; // printer name
    DWORD porNameLen = lstrlen(p2->pPortName)+1;    // port name

    // Allocate a global handle big enough to hold DEVNAMES.
    HGLOBAL hDevNames = GlobalAlloc(GHND,
        sizeof(DEVNAMES) +
        (drvNameLen + ptrNameLen + porNameLen)*sizeof(TCHAR));
    ASSERT(hDevNames);
    DEVNAMES* pDevNames = (DEVNAMES*)GlobalLock(hDevNames);
    ASSERT(pDevNames);

    // Copy the DEVNAMES information from PRINTER_INFO_2
    // tcOffset = TCHAR Offset into structure
    int tcOffset = sizeof(DEVNAMES)/sizeof(TCHAR);
    ASSERT(sizeof(DEVNAMES) == tcOffset*sizeof(TCHAR));

    pDevNames->wDriverOffset = tcOffset;
    memcpy((LPTSTR)pDevNames + tcOffset, p2->pDriverName,
        drvNameLen*sizeof(TCHAR));
    tcOffset += drvNameLen;

    pDevNames->wDeviceOffset = tcOffset;
    memcpy((LPTSTR)pDevNames + tcOffset, p2->pPrinterName,
        ptrNameLen*sizeof(TCHAR));
    tcOffset += ptrNameLen;

    pDevNames->wOutputOffset = tcOffset;
    memcpy((LPTSTR)pDevNames + tcOffset, p2->pPortName,
        porNameLen*sizeof(TCHAR));
    pDevNames->wDefault = 0;

    GlobalUnlock(hDevNames);
    GlobalFree(p2);   // free PRINTER_INFO_2

    // set the new hDevMode and hDevNames
    *phDevMode = hDevMode;
    *phDevNames = hDevNames;
    return TRUE;
}
				

As a quick reference, following is the declaration of DEVNAMES with a short description of each field:

// commdlg.h
// the first three members are character offsets from the beginning of the // structure pointing to the specific string
typedef struct tagDEVNAMES {
   WORD wDriverOffset;  // file name of driver (without extension)
   WORD wDeviceOffset;  // device name
   WORD wOutputOffset;  // device name of physical output medium
   WORD wDefault;       // DN_DEFAULTPRN if default printer chosen
} DEVNAMES;
				

Setting the Application's Default Printer

To set the default printer of the application you need to set the m_hDevNames and m_hDevMode data members (which are protected) through a member function of the CWinApp derived object, GetPrinterDevice(). You can implement the function below and call it whenever you need to change the default printer.

void CMainFrame::OnActionSetnondefaultprinter() 
{
    HGLOBAL hDevMode = NULL;
    HGLOBAL hDevNames = NULL;
    if (GetPrinterDevice(_T("\\\\RED-PRN-25\\PRIV0006"), &hDevNames, &hDevMode))
        AfxGetApp()->SelectPrinter(hDevNames, hDevMode);
    else
        AfxMessageBox(_T("Failed to select custom printer"));
}
				

Bypassing the Print Dialog when Using the Application's Default Printer

To bypass the print dialog, OnPreparePrinting needs to be overridden so that the m_bDirect flag can be set to TRUE. DoPreparePrinting is then called to set the values of pInfo->m_pPD->m_pd.hDevMode and pInfo->m_pPD->m_pd.hDevNames to the corresponding application object's data member and to create the printer DC.

BOOL CNonDefPrinterView::OnPreparePrinting(CPrintInfo* pInfo)
{
    pInfo->m_bDirect = TRUE; // TRUE if bypassing Print Dialog
    return DoPreparePrinting(pInfo);
}
				

Bypassing the Print Dialog when Using a Non-Default Printer

To bypass the print dialog and use a non-default printer, you need to set the pInfo->m_pPD->m_pd data members yourself and create the printer DC. Following is the code that will accomplish this:

BOOL CNonDefPrinterView::OnPreparePrinting(CPrintInfo* pInfo)
{
    // set to non-default printer without changing default app printer
    HGLOBAL hDevMode;
    HGLOBAL hDevNames;

    if (!GetPrinterDevice(_T("\\\\RED-PRN-25\\PRIV0006"), &hDevNames, &hDevMode))
        AfxMessageBox(_T("GetPrinterDevice called failed\n"));

    pInfo->m_pPD->m_pd.hDevMode = hDevMode;
    pInfo->m_pPD->m_pd.hDevNames = hDevNames;
    pInfo->m_pPD->CreatePrinterDC();

    return TRUE;
}
				

This example is shown using the GetPrinterDevice function. See above for more detail.