Fast Track Visual C++ 6.0 Programming
(Publisher: John Wiley & Sons, Inc.)
Author(s): Steve Holzner
ISBN: 0471312908
Publication Date: 09/01/98

We’ve used view hints to redraw only the changed line. In this way, we’re able to coordinate views in a smart way.

Let’s look at one last topic: using the document’s modified flag. This is the flag you set when the user modifies the document so the program prompts the user if he or she exits without saving the document.

Setting the Document’s Modified Flag

Setting the document’s modified flag is easy: We use the document’s SetModifiedFlag() function as shown in the following example:

void CMDIView::OnChar(UINT nChar, UINT nRepCnt, UINT nFlags)

{
    CMDIDoc* pDoc = GetDocument();
    ASSERT_VALID(pDoc);
  
    if(nChar != '\r'){
        pDoc->text[pDoc->number_lines] += nChar;
        Invalidate();
    }
    else{
        pDoc->number_lines++;      
    }
  
    pDoc->UpdateAllViews(this, (long) pDoc->number_lines, NULL);
    pDoc->SetModifiedFlag();                   ⇐

    CView::OnChar(nChar, nRepCnt, nFlags);

}

Figure 2.4  Using the modified flag.

If users quit without saving a modified document, the program prompts them to save the document (we add file handling to our program soon), as shown in Figure 2.4.

That completes our first MDI program. Here, we’ve set up an MDI program, supported multiple documents and views, coordinated multiple views, used view hints, and made use of the document’s modified flag. Our program is a success.

MDIDoc.h and MDIDoc.cpp appear in Listing 2.1, and MDIView.h and MDIView.cpp appear in Listing 2.2.

Listing 2.1 MDIDoc.h and MDIDoc.cpp

// MDIDoc.h : interface of the CMDIDoc class
//
/////////////////////////////////////////////////////////////////////////////

#if 
!defined(AFX_MDIDOC_H__81CAFB2D_9C82_11D1_887F_D42B07C10710__INCLUDED_)
#define AFX_MDIDOC_H__81CAFB2D_9C82_11D1_887F_D42B07C10710__INCLUDED_

#if _MSC_VER > 1000
#pragma once
#endif // _MSC_VER > 1000

const MAX_LINES = 1000;

class CMDIDoc : public CDocument
{
protected: // create from serialization only
    CMDIDoc();
    DECLARE_DYNCREATE(CMDIDoc)
// Attributes
public:
    int number_lines;
    CString text[MAX_LINES];
// Operations
public:

// Overrides
    // ClassWizard generated virtual function overrides
    //{{AFX_VIRTUAL(CMDIDoc)
    public:
    virtual BOOL OnNewDocument();
    virtual void Serialize(CArchive& ar);
    //}}AFX_VIRTUAL

// Implementation
public:
    virtual ~CMDIDoc();
#ifdef _DEBUG
    virtual void AssertValid() const;
    virtual void Dump(CDumpContext& dc) const;
#endif

protected:

// Generated message map functions
protected:
    //{{AFX_MSG(CMDIDoc)
        // NOTE - the ClassWizard will add and remove member functions here.
        //    DO NOT EDIT what you see in these blocks of generated code !
    //}}AFX_MSG
    DECLARE_MESSAGE_MAP()
};

/////////////////////////////////////////////////////////////////////////////

//{{AFX_INSERT_LOCATION}}
// Microsoft Visual C++ will insert additional declarations immediately
before the previous line.

#endif // !defined(AFX_MDIDOC_H__81CAFB2D_9C82_11D1_887F_D42B07C10710__INCLUDED_)


// MDIDoc.cpp : implementation of the CMDIDoc class
//

#include "stdafx.h"
#include "MDI.h"

#include "MDIDoc.h"

#ifdef _DEBUG
#define new DEBUG_NEW
#undef THIS_FILE
static char THIS_FILE[] = __FILE__;
#endif

/////////////////////////////////////////////////////////////////////////////
// CMDIDoc

IMPLEMENT_DYNCREATE(CMDIDoc, CDocument)

BEGIN_MESSAGE_MAP(CMDIDoc, CDocument)
    //{{AFX_MSG_MAP(CMDIDoc)
        // NOTE - the ClassWizard will add and remove mapping macros here.
        //    DO NOT EDIT what you see in these blocks of generated code!
    //}}AFX_MSG_MAP
END_MESSAGE_MAP()

/////////////////////////////////////////////////////////////////////////////
// CMDIDoc construction/destruction

CMDIDoc::CMDIDoc()
{
    // TODO: add one-time construction code here


    number_lines = 0;
}

CMDIDoc::~CMDIDoc()
{
}
BOOL CMDIDoc::OnNewDocument()
{
    if (!CDocument::OnNewDocument())
        return FALSE;

    // TODO: add reinitialization code here
    // (SDI documents will reuse this document)

    return TRUE;
}



/////////////////////////////////////////////////////////////////////////////
// CMDIDoc serialization

void CMDIDoc::Serialize(CArchive& ar)
{
    if (ar.IsStoring())
    {
        // TODO: add storing code here
    }
    else
    {
        // TODO: add loading code here
    }
}

/////////////////////////////////////////////////////////////////////////////
// CMDIDoc diagnostics

#ifdef _DEBUG
void CMDIDoc::AssertValid() const
{

    CDocument::AssertValid();
}

void CMDIDoc::Dump(CDumpContext& dc) const
{
    CDocument::Dump(dc);
}
#endif //_DEBUG

/////////////////////////////////////////////////////////////////////////////

// CMDIDoc commands