How to Store MFC Printer Information in a Document
ID: Q133025
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The information in this article applies to:
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The Microsoft Foundation Classes (MFC), included with:
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Microsoft Visual C++ for Windows, 16-bit edition, versions 1.0, 1.5, 1.51, 1.52
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Microsoft Visual C++, 32-bit Editions, versions 1.0, 2.0, 2.1, 2.2, 4.0, 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.
In the following sections, sample code is given for each of these
considerations.
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);
}
The function prototype for CMyDoc::SetPrinterDeviceDefaults() should be
added to the class definition of CMyDoc in the header file. The following
declarations should also be added to CMyDoc:
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);
}
These routines are similar. They use the same code to allocate a new block
of memory and copy the information from one set of structures to the other.
This ensures that no matter what the application object or document object
does to its respective printer information, the other object is not
affected.
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();
}
The next two member functions, one from the view and the other from the
application, guarantee that the application uses the document's printer
information and that the document's information is updated if the user
changes it.
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();
}
Once these code changes are in place, each object derived from the modified
document class stores its own printer information. Because this could lead
to confusion for users who are used to the standard global printer
configuration model, Microsoft recommends that you include the currently
selected printer name as part of the document title.
Additional query words:
kbinf 1.00 2.00 2.10 2.20 2.50 2.51 2.52 3.00 3.10 4.00 4.10
Keywords : kbcode kbMFC kbPrinting kbVC
Version : 1.00 1.50 1.51 1.52 | 1.00 2.00
Platform : NT WINDOWS
Issue type :
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