How to Store MFC Printer Information in a Document

WINDOWS             | WINDOWS NT

The information in this article applies to:

• The Microsoft Foundation Classes (MFC) included with:

      - Microsoft Visual C++ for Windows, versions 1.0, 1.5, 1.51, 1.52
      - Microsoft Visual C++ 32-bit Edition versions 1.0, 2.0, 2.1,
        2.2, 4.0, and 4.1
  

SUMMARY

This article describes how to store printer information in a CDocument derived class. The printer information can then be used to configure a separate printer for each document derived from this class. This can be useful if there are multiple types of documents (for example, graphs, bitmaps, text, and overheads) that need to be printed on different printers. Storing the printer information in the document ensures that the proper printer is used for each document type.

MORE INFORMATION

There are two things that need to be considered when storing the printer information in the document:

• When copying the information between the application and the document, you must ensure that separate copies of this information are maintained because both the application object and the document free and reallocate memory for the information structures frequently.
• You must trap all changes to the application printer information, so that consistency is maintained between it and the current document object.

Copying Information

Below is an example of code that could be added to the CWinApp-derived class and CDocument-derived class to safely copy information between the objects. It is assumed that CMyApp is a class derived from CWinApp, CMyDoc is derived from CDocument, and CMyView is derived from CView. You need to add the function prototype for SetPrinterDeviceDefaults to the definition of CMyApp in the header file.

   // Note: for 32-bit compilers, replace occurrences of _fmemcpy()
   //       with memcpy() (or add windowsx.h to your include files)

   void CMyApp::SetPrinterDeviceDefaults(HGLOBAL hDevNames,
                                         HGLOBAL hDevMode)
   {
   // Lock the handles to the structures to get pointers
      LPDEVNAMES pDevNames = (LPDEVNAMES)::GlobalLock(hDevNames);
      LPDEVMODE  pDevMode  = (LPDEVMODE)::GlobalLock(hDevMode);

   // Free the old printer information if it exists
      if (m_hDevNames != NULL)
         ::GlobalFree(m_hDevNames);
      if (m_hDevMode != NULL)
         ::GlobalFree(m_hDevMode);

   // Allocate space for the new printer info structures
      m_hDevNames = ::GlobalAlloc(GPTR, ::GlobalSize(hDevNames));
      m_hDevMode = ::GlobalAlloc(GPTR, ::GlobalSize(hDevMode));

   // Lock the new handles
      LPDEVNAMES m_pDevNames = (LPDEVNAMES)::GlobalLock(m_hDevNames);
      LPDEVMODE  m_pDevMode  = (LPDEVMODE)::GlobalLock(m_hDevMode);

   // Copy the printer information into the document
      _fmemcpy(m_pDevNames, pDevNames,
               (size_t)::GlobalSize(hDevNames));
      _fmemcpy(m_pDevMode, pDevMode,
               (size_t)::GlobalSize(hDevMode));

   // Unlock the handles
      ::GlobalUnlock(hDevNames);
      ::GlobalUnlock(hDevMode);

      ::GlobalUnlock(m_hDevNames);
      ::GlobalUnlock(m_hDevMode);
   }

   HGLOBAL m_hDevMode;
   HGLOBAL m_hDevNames;

   void CMyDoc::SetPrinterDeviceDefaults()
   {
   // Allocate the structure to store the returned printer info
      PRINTDLG printDlg;

   // Get the printer information
      AfxGetApp()->GetPrinterDeviceDefaults(&printDlg);

   // Lock the handles to the structures to get pointers
      LPDEVNAMES pDevNames =
       (LPDEVNAMES)::GlobalLock(printDlg.hDevNames);
      LPDEVMODE  pDevMode  = (LPDEVMODE)::GlobalLock(printDlg.hDevMode);

   // Free the old printer information if it exists
      if (m_hDevNames != NULL)
        ::GlobalFree(m_hDevNames);
      if (m_hDevMode != NULL)
        ::GlobalFree(m_hDevMode);

   // Allocate space for the new printer info structures
      m_hDevNames = ::GlobalAlloc(GPTR,
       ::GlobalSize(printDlg.hDevNames));
      m_hDevMode = ::GlobalAlloc(GPTR, ::GlobalSize(printDlg.hDevMode));

   // Lock the new handles
      LPDEVNAMES m_pDevNames = (LPDEVNAMES)::GlobalLock(m_hDevNames);
      LPDEVMODE  m_pDevMode  = (LPDEVMODE)::GlobalLock(m_hDevMode);

   // Copy the printer information into the document
      _fmemcpy(m_pDevNames, pDevNames,
               (size_t)::GlobalSize(printDlg.hDevNames));
      _fmemcpy(m_pDevMode, pDevMode,
               (size_t)::GlobalSize(printDlg.hDevMode));

   // Unlock the handles
      ::GlobalUnlock(printDlg.hDevNames);
      ::GlobalUnlock(printDlg.hDevMode);

      ::GlobalUnlock(m_hDevNames);
      ::GlobalUnlock(m_hDevMode);
   }

Trapping All Changes

Below is a code example that initializes the document's information and traps OnFilePrint and OnFilePrintSetup. OnFilePrintPreview is not included here because its implementation is virtually identical to OnFilePrint.

Here is the modified constructor for the CDocument derived class that initializes the new document with the application's current printer information:

   CMyDoc::CMyDoc()
   {
   // Initialize the handles to the printer information
      m_hDevNames = NULL;
      m_hDevMode = NULL;

   // Initialize printer settings
      SetPrinterDeviceDefaults();
   }

CMyView::OnFilePrint is a message handler for the ID_FILE_PRINT message, and CMyApp::OnFilePrintSetup is a message handler for the ID_FILE_PRINT_SETUP message. The message handlers can be added using ClassWizard.

   void CMyView::OnFilePrint()
   {
      CMyDoc* pDoc = GetDocument();

   // Set the application's printer information
      ((CMyApp *)AfxGetApp())->SetPrinterDeviceDefaults(
                                     pDoc->m_hDevNames,
                                     pDoc->m_hDevMode);

      CView::OnFilePrint();

   // Set the new printer information
      pDoc->SetPrinterDeviceDefaults();
   }

   void CMyApp::OnFilePrintSetup()
   {
      CFrameWnd* pFrame = ((CFrameWnd *)m_pMainWnd)->GetActiveFrame();

      CMyDoc* pDoc = (CMyDoc *)pFrame->GetActiveDocument();

   // Set the application's printer information
      SetPrinterDeviceDefaults(pDoc->m_hDevNames, pDoc->m_hDevMode);

      CWinApp::OnFilePrintSetup();

   // Set the new printer information
      pDoc->SetPrinterDeviceDefaults();
   }