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

Now that we’ve copied the capture region from the screen to out bitmap in memory, we can place it into the clipboard. We do that by opening and emptying the clipboard, using SetClipboardData() to place the data in the clipboard and closing the clipboard again:

void CCopierView::OnRButtonUp(UINT nFlags, CPoint point)

{
    if(CaptureFlag && DrawFlag){

        DrawFlag = false;
            .
            .
            .
        MemoryDC.CreateCompatibleDC(&ScreenDC);
        bitmap.CreateCompatibleBitmap(&ScreenDC, Width, Height);
        MemoryDC.SelectObject(&bitmap);

        MemoryDC.BitBlt(0, 0, Width, Height, &ScreenDC,
LeftUpper.x, LeftUpper.y, SRCCOPY);

        OpenClipboard();                                       ⇐
        EmptyClipboard();                                      ⇐

        SetClipboardData(CF_BITMAP, HBITMAP(bitmap));          ⇐

        CloseClipboard();                                      ⇐
            .
            .
            .
    }

    CView::OnRButtonUp(nFlags, point);

}

This enables the user to use our program to copy sections of the screen into the clipboard. The last step in this program is to display the bitmap in the view.

Displaying a Bitmap in a View

To copy the data in our bitmap to the program’s view, we simply use BitBlt() one more time, this time to the client device context we’ve already set up—ScreenDC:

void CCopierView::OnRButtonUp(UINT nFlags, CPoint point)

{
    if(CaptureFlag && DrawFlag){

        DrawFlag = false;
            .
            .
            .
        MemoryDC.CreateCompatibleDC(&ScreenDC);
        bitmap.CreateCompatibleBitmap(&ScreenDC, Width, Height);
        MemoryDC.SelectObject(&bitmap);

        MemoryDC.BitBlt(0, 0, Width, Height, &ScreenDC,
LeftUpper.x, 
LeftUpper.y, SRCCOPY);

        OpenClipboard();
        EmptyClipboard();

        SetClipboardData(CF_BITMAP, HBITMAP(bitmap));

        CloseClipboard();

        CClientDC dc(this);                               ⇐
        dc.BitBlt(0, 0, Width, Height, &ScreenDC, LeftUpper.x, LeftUpper.y, 
SRCCOPY);                                                 ⇐
    }

    CView::OnRButtonUp(nFlags, point);

}

You are now ready to run the program. Press and hold the left mouse button in the program, then move to the beginning of the capture area. Drag the right mouse button over the capture area, drawing a rectangle, as shown in Figure 6.1.

When you release the right mouse button, the captured region is copied to the clipboard and to our program’s view, as shown in Figure 6.2. Now we’re able to perform screen capture.

The code for this example, CopierView.h and CopierView.cpp, appear in Listing 6.1.

Listing 6.1 CopierView.h and CopierView.cpp

// CopierView.h : interface of the CCopierView class
//
/////////////////////////////////////////////////////////////////////////////

#if 
!defined(AFX_COPIERVIEW_H__44745D0F_A238_11D1_887F_
D42B07C10710__INCLUDED_)
#define AFX_COPIERVIEW_H__44745D0F_A238_11D1_887F_
D42B07C10710__INCLUDED_


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

class CCopierView : public CView
{
protected: // create from serialization only
    CCopierView();
    DECLARE_DYNCREATE(CCopierView)
    bool CaptureFlag, DrawFlag;
    CPoint AnchorPoint, PreviousPoint;

// Attributes
public:
    CCopierDoc* GetDocument();

// Operations

public:

// Overrides
    // ClassWizard generated virtual function overrides
    //{{AFX_VIRTUAL(CCopierView)
    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 ~CCopierView();


#ifdef _DEBUG
    virtual void AssertValid() const;
    virtual void Dump(CDumpContext& dc) const;
#endif

protected:

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

#ifndef _DEBUG  // debug version in CopierView.cpp
inline CCopierDoc* CCopierView::GetDocument()
   { return (CCopierDoc*)m_pDocument; }
#endif

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

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

#endif // !defined(AFX_COPIERVIEW_H__44745D0F_A238_11D1_887F_
D42B07C10710__INCLUDED_)


// CopierView.cpp : implementation of the CCopierView class
//

#include "stdafx.h"
#include "Copier.h"

#include "CopierDoc.h"


#include "CopierView.h"

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


/////////////////////////////////////////////////////////////////////////////
// CCopierView

IMPLEMENT_DYNCREATE(CCopierView, CView)

BEGIN_MESSAGE_MAP(CCopierView, CView)
    //{{AFX_MSG_MAP(CCopierView)
    ON_WM_LBUTTONDOWN()
    ON_WM_LBUTTONUP()
    ON_WM_MOUSEMOVE()
    ON_WM_RBUTTONDOWN()
    ON_WM_RBUTTONUP()
    //}}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()

/////////////////////////////////////////////////////////////////////////////
// CCopierView construction/destruction

CCopierView::CCopierView()
{
    // TODO: add construction code here
    CaptureFlag = false;
    DrawFlag = false;
}

CCopierView::~CCopierView()
{
}



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

    return CView::PreCreateWindow(cs);
}

/////////////////////////////////////////////////////////////////////////////
// CCopierView drawing

void CCopierView::OnDraw(CDC* pDC)
{
    CCopierDoc* pDoc = GetDocument();
    ASSERT_VALID(pDoc);

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

/////////////////////////////////////////////////////////////////////////////
// CCopierView printing

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

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

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

/////////////////////////////////////////////////////////////////////////////
// CCopierView diagnostics



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

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

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

/////////////////////////////////////////////////////////////////////////////
// CCopierView message handlers

void CCopierView::OnLButtonDown(UINT nFlags, CPoint point)
{
    // TODO: Add your message handler code here and/or call default
    SetCapture();
    CaptureFlag = true;
    DrawFlag = false;

    CView::OnLButtonDown(nFlags, point);
}

void CCopierView::OnLButtonUp(UINT nFlags, CPoint point)
{
    // TODO: Add your message handler code here and/or call default
    ReleaseCapture();
    CaptureFlag = false;
    DrawFlag = false;

    CView::OnLButtonUp(nFlags, point);
}



void CCopierView::OnMouseMove(UINT nFlags, CPoint point)
{
    // TODO: Add your message handler code here and/or call default
    if(CaptureFlag && DrawFlag){
        CDC ScreenDC;

        CPoint CurrentPoint = GetMessagePos();

        ScreenDC.CreateDC("DISPLAY", NULL, NULL, NULL);
        ScreenDC.SelectStockObject(NULL_BRUSH);
        ScreenDC.SetROP2(R2_NOT);
        ScreenDC.Rectangle(CRect(PreviousPoint, AnchorPoint));
        ScreenDC.Rectangle(CRect(AnchorPoint, CurrentPoint));

        PreviousPoint = CurrentPoint;
    }

    CView::OnMouseMove(nFlags, point);
}

void CCopierView::OnRButtonUp(UINT nFlags, CPoint point)
{
    // TODO: Add your message handler code here and/or call default

    if(CaptureFlag && DrawFlag){

        DrawFlag = false;

        int Width, Height;
        CPoint CurrentPoint = GetMessagePos();
        CDC ScreenDC;

        ScreenDC.CreateDC("DISPLAY", NULL, NULL, NULL);
        ScreenDC.SelectStockObject(NULL_BRUSH);
        ScreenDC.SetROP2(R2_NOT);

        ScreenDC.Rectangle(CRect(AnchorPoint, PreviousPoint));

        CPoint LeftUpper(min(AnchorPoint.x, CurrentPoint.x),
min(AnchorPoint.y, CurrentPoint.y));



        Height = abs(AnchorPoint.y - CurrentPoint.y);
        Width = abs(AnchorPoint.x - CurrentPoint.x);

        CDC MemoryDC;
        CBitmap bitmap;

        MemoryDC.CreateCompatibleDC(&ScreenDC);
        bitmap.CreateCompatibleBitmap(&ScreenDC, Width, Height);
        MemoryDC.SelectObject(&bitmap);

        MemoryDC.BitBlt(0, 0, Width, Height, &ScreenDC,
LeftUpper.x, LeftUpper.y, SRCCOPY);

        OpenClipboard();
        EmptyClipboard();

        SetClipboardData(CF_BITMAP, HBITMAP(bitmap));

        CloseClipboard();

        CClientDC dc(this);
        dc.BitBlt(0, 0, Width, Height, &ScreenDC, LeftUpper.x,
LeftUpper.y, SRCCOPY);
    }

    CView::OnRButtonUp(nFlags, point);

}