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

Listing 6.2 Redraw.h

class CRedraw
{
protected:
    CMetaFileDC* pDC;
public:
    CRedraw(){pDC = new CMetaFileDC();


                pDC->Create();}

    ~CRedraw(){delete pDC;}

    CMetaFileDC* GetDC() {return pDC;}

    void PlayMetaFile(CDC* pRefreshDC){

        HMETAFILE OldMetaFileHandle = pDC->Close();
        if(OldMetaFileHandle == NULL)
            return;

        pRefreshDC->PlayMetaFile(OldMetaFileHandle);

        CMetaFileDC* ReplacementMetaFile = new CMetaFileDC();
        ReplacementMetaFile->Create();
        ReplacementMetaFile->PlayMetaFile(OldMetaFileHandle);

        DeleteMetaFile(OldMetaFileHandle);
        delete pDC;

        pDC = ReplacementMetaFile;}

};

Listing 6.3 CirclesView.h and CirclesView.cpp

// CirclesView.h : interface of the CCirclesView class
//
/////////////////////////////////////////////////////////////////////////////

#if 
!defined(AFX_CIRCLESVIEW_H__9036416F_A23B_11D1_887F_
D42B07C10710__INCLUDED_)
#define AFX_CIRCLESVIEW_H__9036416F_A23B_11D1_887F_
D42B07C10710__INCLUDED_

#if _MSC_VER > 1000
#pragma once
#endif // _MSC_VER > 1000
#include "Redraw.h"

class CCirclesView : public CView
{

protected: // create from serialization only
    CCirclesView();
    DECLARE_DYNCREATE(CCirclesView)
    CPoint point1, point2;
    CRedraw redraw;
// Attributes
public:
    CCirclesDoc* GetDocument();

// Operations
public:

// Overrides
    // ClassWizard generated virtual function overrides
    //{{AFX_VIRTUAL(CCirclesView)
    public:
    virtual void OnDraw(CDC* pDC);  // overridden to draw this view
    virtual BOOL PreCreateWindow(CREATESTRUCT& cs);
    protected:
    virtual BOOL OnPreparePrinting(CPrintInfo* pInfo);
    virtual void OnBeginPrinting(CDC* pDC, CPrintInfo* pInfo);
    virtual void OnEndPrinting(CDC* pDC, CPrintInfo* pInfo);
    //}}AFX_VIRTUAL

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

protected:

// Generated message map functions
protected:
    //{{AFX_MSG(CCirclesView)
    afx_msg void OnLButtonDown(UINT nFlags, CPoint point);
    afx_msg void OnLButtonUp(UINT nFlags, CPoint point);
    //}}AFX_MSG
    DECLARE_MESSAGE_MAP()


};

#ifndef _DEBUG  // debug version in CirclesView.cpp
inline CCirclesDoc* CCirclesView::GetDocument()
   { return (CCirclesDoc*)m_pDocument; }
#endif

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

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

#endif // !defined(AFX_CIRCLESVIEW_H__9036416F_A23B_11D1_887F_
D
42B07C10710__INCLUDED_)


// CirclesView.cpp : implementation of the CCirclesView class
//

#include "stdafx.h"
#include "Circles.h"

#include "CirclesDoc.h"
#include "CirclesView.h"

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


/////////////////////////////////////////////////////////////////////////////
// CCirclesView

IMPLEMENT_DYNCREATE(CCirclesView, CView)

BEGIN_MESSAGE_MAP(CCirclesView, CView)
    //{{AFX_MSG_MAP(CCirclesView)
    ON_WM_LBUTTONDOWN()


    ON_WM_LBUTTONUP()
    //}}AFX_MSG_MAP
    // Standard printing commands
    ON_COMMAND(ID_FILE_PRINT, CView::OnFilePrint)
    ON_COMMAND(ID_FILE_PRINT_DIRECT, CView::OnFilePrint)
    ON_COMMAND(ID_FILE_PRINT_PREVIEW, CView::OnFilePrintPreview)
END_MESSAGE_MAP()

/////////////////////////////////////////////////////////////////////////////
// CCirclesView construction/destruction

CCirclesView::CCirclesView()
{
    // TODO: add construction code here
    point1.x = -1;
    point1.y = -1;
}

CCirclesView::~CCirclesView()
{
}

BOOL CCirclesView::PreCreateWindow(CREATESTRUCT& cs)
{
    // TODO: Modify the Window class or styles here by modifying
    //  the CREATESTRUCT cs

    return CView::PreCreateWindow(cs);
}

/////////////////////////////////////////////////////////////////////////////
// CCirclesView drawing

void CCirclesView::OnDraw(CDC* pDC)
{
    CCirclesDoc* pDoc = GetDocument();
    ASSERT_VALID(pDoc);
    redraw.PlayMetaFile(pDC);

    // TODO: add draw code for native data here
}



/////////////////////////////////////////////////////////////////////////////
// CCirclesView printing

BOOL CCirclesView::OnPreparePrinting(CPrintInfo* pInfo)
{
    // default preparation
    return DoPreparePrinting(pInfo);
}

void CCirclesView::OnBeginPrinting(CDC* /*pDC*/, CPrintInfo* /*pInfo*/)
{
    // TODO: add extra initialization before printing
}

void CCirclesView::OnEndPrinting(CDC* /*pDC*/, CPrintInfo* /*pInfo*/)
{
    // TODO: add cleanup after printing
}

/////////////////////////////////////////////////////////////////////////////
// CCirclesView diagnostics

#ifdef _DEBUG
void CCirclesView::AssertValid() const
{
    CView::AssertValid();
}

void CCirclesView::Dump(CDumpContext& dc) const
{
    CView::Dump(dc);
}

CCirclesDoc* CCirclesView::GetDocument() // non-debug version is inline
{
    ASSERT(m_pDocument->IsKindOf(RUNTIME_CLASS(CCirclesDoc)));
    return (CCirclesDoc*)m_pDocument;
}
#endif //_DEBUG


/////////////////////////////////////////////////////////////////////////////
// CCirclesView message handlers

void CCirclesView::OnLButtonDown(UINT nFlags, CPoint point) 
{
    point1 = point;
    
    CView::OnLButtonDown(nFlags, point);
}

void CCirclesView::OnLButtonUp(UINT nFlags, CPoint point) 
{
    point2 = point;

    CClientDC* pDC;
    pDC = new CClientDC(this);

    pDC->Ellipse(point1.x, point1.y, point2.x, point2.y);
    redraw.GetDC()->Ellipse(point1.x, point1.y, point2.x, point2.y);

    CView::OnLButtonUp(nFlags, point);

}

What’s Ahead

In the next chapter, we work with the ins and outs of 32-bit memory handling, including scanning memory to see what’s there, allocating and deallocating memory, and communicating between processes using shared memory. This is a popular programming topic, so let’s start our exploration