Programming with Microsoft Visual C++.NET 6ed [Electronic resources] نسخه متنی

The Ex17b Example: A Multi-Page Print Program

In this example, the document contains an array of 50 CRect objects that define circles. The circles are randomly positioned in a 6-by-6-inch area and have random diameters of as much as 0.5 inch. The circles, when drawn on the display, look like two-dimensional simulations of soap bubbles. Instead of drawing the circles on the printer, the application prints the corresponding CRect coordinates in numeric form, 12 to a page, with headers and footers. Here are the steps:

Run the MFC Application Wizard to generate a project named Ex17b. Select Single Document, and accept the defaults for all the other settings.





Edit the

StdAfx.h header file. You'll need to bring in the declarations for the MFC template collection classes. Add the following statement:

#include <afxtempl.h>






Edit the

Ex17bDoc.h header file. In the Ex17a example, the document data consists of strings stored in a CStringArray collection. Because we're using a template collection for ellipse rectangles, we'll need a typedef statement outside the class declaration, as shown here:

 typedef CArray<CRect, CRect&> CRectArray;




Next, add the following public data members to the

Ex17bDoc.h header file:

public:
enum { nLinesPerPage = 12 };
enum { nMaxEllipses = 50 };
CRectArray m_ellipseArray;




The two enumerations are object-oriented replacements for #defines.





Edit the

Ex17bDoc.cpp implementation file. The overridden OnNewDocument function initializes the ellipse array with some random values, and the Serialize function reads and writes the whole array. The MFC Application Wizard generated the skeletons for both functions. You don't need a DeleteContents function because the CArray subscript operator writes a new CRect object on top of any existing one. Add the following boldface code:

BOOL CEx17bDoc::OnNewDocument()
{
if (!CDocument::OnNewDocument())
return FALSE;
    int n1, n2, n3;
    // Make 50 random circles
    srand((unsigned) time(NULL));
    m_ellipseArray.SetSize(nMaxEllipses);
    for (int i = 0; i < nMaxEllipses; i++) {
        n1 = rand() * 600 / RAND_MAX;
        n2 = rand() * 600 / RAND_MAX;
        n3 = rand() * 50  / RAND_MAX;
        m_ellipseArray[i] = CRect(n1, -n2, n1 + n3, -(n2 + n3));
}
return TRUE;
}
void CEx17bDoc::Serialize(CArchive& ar)
{
    m_ellipseArray.Serialize(ar);
}








Edit the

Ex17bView.h header file. Use the Add Member Variable Wizard and the Add Member Function Wizard, both available from Class View, to add the member variable and two function prototypes listed below. The Add Member Function Wizard will also generate skeletons for the functions in

Ex17bView.cpp .

public:
int m_nPage;
private:
void PrintPageHeader(CDC *pDC);
void PrintPageFooter(CDC *pDC);




The m_nPage data member holds the document's current page number for printing. The private functions are for the header and footer subroutines.





Edit the OnDraw function in

Ex17bView.cpp . The overridden OnDraw function simply draws the bubbles in the view window. Add the boldface code shown here:

void CEx17bView::OnDraw(CDC* pDC)
{
int i, j;
CEx17bDoc* pDoc = GetDocument();
    j = pDoc->m_ellipseArray.GetUpperBound();
    for (i = 0; i < j; i++) {
        pDC->Ellipse(pDoc->m_ellipseArray[i]);
}
}






Insert the OnPrepareDC function in

Ex17bView.cpp . The view class is not a scrolling view, so the mapping mode must be set in this function. Use Class View's Properties window to override the OnPrepareDC function, and then add the following boldface code:

void CEx17bView::OnPrepareDC(CDC* pDC, CPrintInfo* pInfo)
{
pDC->SetMapMode(MM_LOENGLISH);
}






Insert the OnPrint function in

Ex17bView.cpp . The CView default OnPrint function calls OnDraw. In this example, we want the printed output to be entirely different from the displayed output, so the OnPrint function must take care of the print output without calling OnDraw. OnPrint first sets the mapping mode to MM_TWIPS, and then it creates a fixed-pitch font. After printing the numeric contents of 12 m_ellipseArray elements, OnPrint deselects the font. You could have created the font once in OnBeginPrinting, but you wouldn't have noticed the increased efficiency. Use Class View's Properties window to override the OnPrint function, and then add the following boldface code:

void CEx17bView::OnPrint(CDC* pDC, CPrintInfo* pInfo)
{
    int        i, nStart, nEnd, nHeight;
    CString    str;
    CPoint     point(720, -1440);
    CFont      font;
    TEXTMETRIC tm;
    pDC->SetMapMode(MM_TWIPS);
    CEx17bDoc* pDoc = GetDocument();
    m_nPage = pInfo->m_nCurPage; // for PrintPageFooter's benefit
    nStart = (m_nPage - 1) * CEx17bDoc::nLinesPerPage;
    nEnd = nStart + CEx17bDoc::nLinesPerPage;
     // 14-point fixed-pitch font
    font.CreateFont(-280, 0, 0, 0, 400, FALSE, FALSE,
                    0, ANSI_CHARSET, OUT_DEFAULT_PRECIS,
                    CLIP_DEFAULT_PRECIS, DEFAULT_QUALITY,
                    DEFAULT_PITCH | FF_MODERN, "Courier New");
                    // Courier New is a TrueType font
    CFont* pOldFont = (CFont*) (pDC->SelectObject(&font));
    PrintPageHeader(pDC);
    pDC->GetTextMetrics(&tm);
    nHeight = tm.tmHeight + tm.tmExternalLeading;
    for (i = nStart; i < nEnd; i++) {
        if (i > pDoc->m_ellipseArray.GetUpperBound()) {
            break;
        }
        str.Format("%6d %6d %6d %6d %6d", i + 1,
                   pDoc->m_ellipseArray[i].left,
                   pDoc->m_ellipseArray[i].top,
                   pDoc->m_ellipseArray[i].right,
                   pDoc->m_ellipseArray[i].bottom);
        point.y -= nHeight;
        pDC->TextOut(point.x, point.y, str);
    }
    PrintPageFooter(pDC);
    pDC->SelectObject(pOldFont);
}








Edit the OnPreparePrinting function in

Ex17bView.cpp . The OnPreparePrinting function (whose skeleton is generated by the MFC Application Wizard) computes the number of pages in the document and then communicates that value to the application framework through the SetMaxPage function. Add the following boldface code:

BOOL CEx17bView::OnPreparePrinting(CPrintInfo* pInfo)
{
    CEx17bDoc* pDoc = GetDocument();
    pInfo->SetMaxPage(pDoc->m_ellipseArray.GetUpperBound() /
                      CEx17bDoc::nLinesPerPage + 1);
return DoPreparePrinting(pInfo);
}






Insert the page header and footer functions in

Ex17bView.cpp . These private functions, called from OnPrint, print the page headers and the page footers. The page footer includes the page number, stored by OnPrint in the view class data member m_nPage. The CDC::GetTextExtent function provides the width of the page number so that it can be right-justified. Add the boldface code shown here:

void CEx17bView::PrintPageHeader(CDC* pDC)
{
    CString str;
    CPoint point(0, 0);
    pDC->TextOut(point.x, point.y, "Bubble Report");
    point += CSize(720, -720);
    str.Format("%6.6s %6.6s %6.6s %6.6s %6.6s",
               "Index", "Left", "Top", "Right", "Bottom");
    pDC->TextOut(point.x, point.y, str);
}
void CEx17bView::PrintPageFooter(CDC* pDC)
{
CString str;
    CPoint point(0, -14400); // Move 10 inches down
    CEx17bDoc* pDoc = GetDocument();
    str.Format("Document %s", (LPCSTR) pDoc->GetTitle());
    pDC->TextOut(point.x, point.y, str);
    str.Format("Page %d", m_nPage);
    CSize size = pDC->GetTextExtent(str);
    point.x += 11520 - size.cx;
    pDC->TextOut(point.x, point.y, str); // right-justified
}






Build and test the application. For one set of random numbers, the bubble view window looks like this:




Each time you choose New from the File menu, you should see a different picture. In Print Preview, the first page of the output should look like this:







In the Print dialog box, you can specify any range of pages to print.