www.pudn.com > NetTraffic.rar > MemDC.h

#if !defined(AFX_MEMDC_H__CA1D3541_7235_11D1_ABBA_00A0243D1382__INCLUDED_) 
#define AFX_MEMDC_H__CA1D3541_7235_11D1_ABBA_00A0243D1382__INCLUDED_ 
 
#if _MSC_VER >= 1000 
#pragma once 
#endif // _MSC_VER >= 1000 
 
////////////////////////////////////////////////// 
// CMemDC 实现一个内存DC 
 
class CMemDC : public CDC 
{ 
private: 
    CBitmap  m_bitmap;      // 实际的bitmap 
    CBitmap* m_pOldBitmap;  // 原先在CMemDC中的位图 
    CDC*     m_pDC;         // 保存从构造函数中传来的CDC 
    CRect    m_rect;        // 画的矩形区域 
    BOOL     m_bMemDC;      // 如果CDC是一个内存DC，则为TRUE 
 
public: 
 
    CMemDC(CDC* pDC) : CDC() 
    { 
        ASSERT(pDC != NULL); 
 
        m_pDC = pDC; 
        m_pOldBitmap = NULL; 
        m_bMemDC = !pDC->IsPrinting();//判断是否是一个内存DC 
               
        if (m_bMemDC)    // 创建一个内存DC 
        { 
            pDC->GetClipBox(&m_rect); 
            CreateCompatibleDC(pDC); 
            m_bitmap.CreateCompatibleBitmap(pDC, m_rect.Width(), m_rect.Height()); 
            m_pOldBitmap = SelectObject(&m_bitmap); 
            SetWindowOrg(m_rect.left, m_rect.top); 
        } 
        else  // 这不是一个内存DC，我们只拷贝相关的DC部分以备打印 
        { 
            m_bPrinting = pDC->m_bPrinting; 
            m_hDC       = pDC->m_hDC; 
            m_hAttribDC = pDC->m_hAttribDC; 
        } 
    } 
    
    ~CMemDC() 
    { 
        if (m_bMemDC)  
        {     
            // 拷贝实际的位图到屏幕上 
            m_pDC->BitBlt(m_rect.left, m_rect.top, m_rect.Width(), m_rect.Height(), 
                          this, m_rect.left, m_rect.top, SRCCOPY); 
            //装入原始的位图 
            SelectObject(m_pOldBitmap); 
        }  
		else  
		{ 
            m_hDC = m_hAttribDC = NULL; 
        } 
    } 
 
    // 允许作为指针 
    CMemDC* operator->() {return this;} 
    operator CMemDC*() {return this;} 
 
}; 
 
///////////////////////////////////////////////////////////////////////////// 
 
//{{AFX_INSERT_LOCATION}} 
// Microsoft Developer Studio will insert additional declarations immediately before the previous line. 
 
#endif // !defined(AFX_MEMDC_H__CA1D3541_7235_11D1_ABBA_00A0243D1382__INCLUDED_)