How To Change the Default Source of Printer Programmatically

The information in this article applies to:

• Microsoft Visual FoxPro for Windows, versions 3.0, 3.0b, 5.0

SUMMARY

To set the default source (upper/lower tray) of a printer programmatically under Windows 95 and Windows NT 4.0, use the SetPrinter() Win32 API function.

Note that the SetPrinter() API call is platform-dependent and works only on Windows 95 and Windows NT 4.0. (It does not work on earlier versions of Windows NT or on a 16-bit platform.)

MORE INFORMATION

To set or change the default source of printer under Windows 95 and Windows NT 4.0, call the following:

   SetPrinter(HANDLE hPrinter, DWORD dwLevel, LPBYTE lpbPrinter, DWORD

Obtain the hPrinter parameter from OpenPrinter() as a handle that identifies the desired printer. Set the dwLevel parameter to 2, and point lpbPrinter to the PRINTER_INFO_2 structure. Set the dwCommand parameter to 0. Fill out the PRINTER_INFO_2 structure appropriately.

There are few ways of changing the (upper/lower) printer tray dynamically. The most common is to use PCL printer commands. To do this, insert the escape sequence in the file, along with the content you are trying to print. Unfortunately, this method makes it difficult to work with Visual FoxPro since you are limited by the printer's settings (you need to know the designated printer beforehand), and the reports in Visual FoxPro use the printer driver internally once the printing job is established.

The following sample program illustrates the contents of the .dll file written in Microsoft Visual C++ 4.0. It shows a way to retrieve a handle identifying the specified printer or print server.

NOTE: This sample program illustrates many Microsoft Visual C++ commands. The use of these commands is beyond the scope of Microsoft FoxPro Product Support. Users with substantial experience using API routines should be able to write the following sample .dll file. For this sample to work, you need a .def file to export the chgbin function.

Sample Program (DLL to Change the Default Source of Printer)

#include "stdio.h"
#include <windows.h>

     return 1;
     UNREFERENCED_PARAMETER(hInst);
     UNREFERENCED_PARAMETER(ul_reason_being_called);
     UNREFERENCED_PARAMETER(lpReserved);

#define ErrReturn   if (GetLastError()) {ClosePrinter(hPrinter);

short FindID(LPPRINTER_INFO_2 pPrinter, int flg);

BOOL MyFreeMem(LPVOID pMem) {

   return VirtualFree(pMem, 0, MEM_RELEASE);

#define UPPER_BIN 1
#define LOWER_BIN 2


int APIENTRY chgbin(char *ptrname, int flg)

   HANDLE   hPrinter = NULL;
   DWORD    cbBuf;
   DWORD    pcbNeeded = 0;
   LPTSTR   pPrintername;
   short    nSource;

   pPrintername = ptrname;

   PRINTER_DEFAULTS pd;
   ZeroMemory(&pd, sizeof(pd));
   pd.DesiredAccess = PRINTER_ALL_ACCESS;

   int result1 = OpenPrinter(pPrintername,&hPrinter, &pd);
   ErrReturn;
   int result = GetPrinter(hPrinter, 2, NULL, 0, &pcbNeeded);
   DWORD Error = GetLastError( );

    if( Error == ERROR_INSUFFICIENT_BUFFER )
    {
   BOOL  bRet = FALSE;
                HANDLE  hMem = NULL;
   LPPRINTER_INFO_2  pPrinter;

        hMem = GlobalAlloc(GHND, pcbNeeded);
        if (hMem) pPrinter = (LPPRINTER_INFO_2)GlobalLock(hMem);
        cbBuf = pcbNeeded;
   DWORD cbNeeded;
   if (GetPrinter(hPrinter, 2, (LPBYTE)pPrinter, pcbNeeded, &cbNeeded))
   {
      if ((nSource = FindID(pPrinter,flg)) < 0) return -1;

      pPrinter->pDevMode->dmDefaultSource = nSource;
      pPrinter->pDevMode->dmFields = DM_DEFAULTSOURCE;

      DocumentProperties(NULL,hPrinter,pPrintername,pPrinter-

            DM_IN_BUFFER|DM_OUT_BUFFER);
      SetPrinter(hPrinter,2,(unsigned char *)pPrinter,0);

      MyFreeMem(pPrinter);
      ClosePrinter(hPrinter);
   }
    }

    Error = GetLastError( );
    return 0;

typedef struct _tagDevCaps {

   TCHAR    pPrinterName[80];
   TCHAR    pPort[80];
   WORD  wCurCap;
   WORD    wCurPlatForm;
   HINSTANCE hDriver;   //only used if on Win32s;
   DWORD  (CALLBACK* pfnDevCaps) (
      LPTSTR    pDevice,   // address of device-name string
      LPTSTR    pPort,  // address of port-name string
      UINT      fwCapability, // device capability to query
      LPTSTR    pOutput,   // address of the output
      LPDEVMODE pDevMode   // address of structure with device data
   );

LPVOID MyAllocMem(DWORD cb) {

   return VirtualAlloc(NULL, cb, MEM_RESERVE|MEM_COMMIT, PAGE_READWRITE);

#define MAX_AMOUNT      256
#define MAX_BINS   16

   DEVCAPS MyDevCaps;
   MyDevCaps.hDriver = NULL;
   MyDevCaps.pfnDevCaps = NULL;
   BOOL bRet = FALSE;

   lstrcpy(MyDevCaps.pPrinterName,  pPrinter->pPrinterName);
   lstrcpy(MyDevCaps.pPort,  pPrinter->pPortName);
   MyDevCaps.pfnDevCaps = (LPFNDEVCAPS)&DeviceCapabilities;

   DWORD       dwBufSize = 0;
   BOOL        bResult = 1;
   WORD FAR    *pawBinList;

   if (MyDevCaps.pfnDevCaps)
   {
       // get number of bins
       dwBufSize = MyDevCaps.pfnDevCaps ((LPTSTR )MyDevCaps.pPrinterName,

                                   (LPTSTR )NULL, (LPDEVMODE)NULL);

       pawBinList = (WORD FAR *)MyAllocMem(dwBufSize* (sizeof(WORD)));

       // fill buffer with bin list
       MyDevCaps.pfnDevCaps ((LPTSTR )MyDevCaps.pPrinterName, (LPTSTR

                       (LPTSTR )pawBinList, (LPDEVMODE)NULL);

       // display bin info
       // protects from bad drivers

        if ((dwBufSize > 0) && (dwBufSize < MAX_AMOUNT))
        {
      for (int i=0; i< (int)dwBufSize;i++)
      {
           if (pawBinList[i] < MAX_AMOUNT)
           {
                    if (pawBinList[i] < MAX_BINS)
          {
                 if (flg == UPPER_BIN && pawBinList[i] == UPPER_BIN)
            return (pawBinList[i]);
              else if (flg == LOWER_BIN && pawBinList[i] == LOWER_BIN)
            return (pawBinList[i]);
          }
           }
      }
        }
       // clean up
       MyFreeMem(pawBinList);

       return (-1);
   }
   return (-1);

In the FoxPro Application

   DECLARE integer chgbin IN c:\bin.DLL STRING, INTEGER

   ** 1 = Upper   2 = Lower
   retval = chgbin("HP LaserJet 4Si MX",2)

   USE CUSTOMER
   LIST TO PRINT

Sample Program (Notes)

• To create a .dll file in Visual C++, please refer to Help in Microsoft Visual C++ 4.0.
• The Chgbin.dll should be in the same directory as your project, or should be in the path of the Windows Win32 directory.

The function chgbin takes two parameters. The first parameter takes the actual printer name. You could get the printer name from FoxPro by using the APRINTER() function, which retrieves all the existing drivers in the current windows operating system. The second parameter is a flag that tells the chgbin function how to set the upper/lower tray. The numeric value 1 indicates that the upper tray should be used, and the numeric value 2 indicates that the lower tray is being used.

This DLL does not work properly if the printer is a network printer. The network printer cannot be configured programmatically since multiple users need to access the printer at the same time. In order to solve this problem, you need to add a local printer driver and force the local driver to print to a file (where the file is redirected to network printer address). In this way, the printer driver can have its own settings, which can be used by a FoxPro application to refer to the network printer.

It is highly recommended to change the setting back to its default (or previous setting) once the program is terminated since other applications might use the same driver.

Visual FoxPro stores the printer and bin to use inside the .frx file for reports. So changing the paper source for the Printer Driver in Windows does not cause the Report to print to a different paper source.

REFERENCES

For more information about Changing the default printer source, please see the following article in the Microsoft Knowledge Base:

   ARTICLE-ID: Q133163
   TITLE     : How to Control Printer Attributes for a Report at Run Time