Re: CView and bitmap problem

From:

"AliR $VC++ MVP$" <AliR@online.nospam>

Newsgroups:

microsoft.public.vc.mfc

Date:

Tue, 31 Mar 2009 14:39:32 -0500

Message-ID:

<HhuAl.4699$Lr6.2023@flpi143.ffdc.sbc.com>

Make sure your view classes follows this kind of logic.

class CDrawingSampleView : public CView
{
protected: // create from serialization only
CDrawingSampleView();
DECLARE_DYNCREATE(CDrawingSampleView)

// Implementation
public:
    virtual ~CDrawingSampleView();

// Generated message map functions
protected:
   virtual void OnDraw(CDC* pDC); // overridden to draw this view
   virtual BOOL PreCreateWindow(CREATESTRUCT& cs);
   virtual void OnInitialUpdate();

   afx_msg BOOL OnEraseBkgnd(CDC* pDC);
   afx_msg void OnDrawLine();
   afx_msg void OnDrawRect();
   DECLARE_MESSAGE_MAP()

private:
   CBitmap m_MemBitmap;
};

}

void CDrawingSampleView::OnInitialUpdate()
{
   CView::OnInitialUpdate();

   CDC *pDC = GetDC();
   //create the bitmap
   m_MemBitmap.CreateCompatibleBitmap(pDC,800,600);

   //create a dc to initialize the bitmap with
   CDC MemDC;
   MemDC.CreateCompatibleDC(pDC);

   ReleaseDC(pDC);

    //make the bitmap white to begin with
   CBitmap *pOldBmp = MemDC.SelectObject(&m_MemBitmap);
   MemDC.FillSolidRect(0,0,800,600,RGB(255,255,255));
   MemDC.SelectObject(pOldBmp);

}

//don't erase background because OnDraw will paint over the entire client
area
BOOL CDrawingSampleView::OnEraseBkgnd(CDC* pDC)
{
   return TRUE;
}

// CDrawingSampleView drawing

void CDrawingSampleView::OnDraw(CDC* pDC)
{
    //draw whatever is in the bitmap on the screen, stretch to fit entire
screen
   CDC MemDC;
   MemDC.CreateCompatibleDC(pDC);
   int SavedDC = MemDC.SaveDC();

   MemDC.SelectObject(&m_MemBitmap);

   CRect Rect;
   GetClientRect(&Rect);
   pDC->StretchBlt(0,0,Rect.Width(),Rect.Height(),&MemDC,0,0,800,600,SRCCOPY);

   MemDC.RestoreDC(SavedDC);
}

//draw a random line on the memory bitmap
void CDrawingSampleView::OnDrawLine()
{
   CDC *pDC = GetDC();
   CDC MemDC;
   MemDC.CreateCompatibleDC(pDC);
   ReleaseDC(pDC);

   CBitmap *pOldBitmap = MemDC.SelectObject(&m_MemBitmap);
   MemDC.SelectStockObject(BLACK_PEN);
   MemDC.MoveTo(rand()%800,rand()%600);
   MemDC.LineTo(rand()%800,rand()%600);
   MemDC.SelectObject(pOldBitmap);

   Invalidate();
   UpdateWindow();
}

//draw a random rect on the memory bitmap
void CDrawingSampleView::OnDrawRect()
{
   CDC *pDC = GetDC();
   CDC MemDC;
   MemDC.CreateCompatibleDC(pDC);
   ReleaseDC(pDC);

   CBitmap *pOldBitmap = MemDC.SelectObject(&m_MemBitmap);
   MemDC.SelectStockObject(BLACK_PEN);
   MemDC.Rectangle(rand()%800,rand()%600,rand()%800,rand()%600);
   MemDC.SelectObject(pOldBitmap);

   Invalidate();
   UpdateWindow();
}

AliR.