CMemoryDC双缓冲.docx

声明CMemoryDC类的头文件MemoryDC.h如下：#pragma once#include Afxwin.hclass CMemoryDCpublic: CMemoryDC(CDC *dc, RECT * rect,bool autoRender = false); CMemoryDC(void); bool IsOK(); void Render(CDC * p_objectDC = NULL); CDC* GetMemoryDC(); operator CDC * ();private: bool m_bAutoRender; CRect m_DCRect; CDC* m_pOriginalDC; CDC m_MemoryDC; CBitmap m_MemoryBmp;类的实现文件CMemoryDC.cpp如下：#include .MemoryDC.hCMemoryDC:CMemoryDC(CDC *dc, RECT * rect, bool autoRender) m_bAutoRender = autoRender; m_pOriginalDC = dc; if (dc=NULL | rect=NULL) return; if (!m_MemoryDC.CreateCompatibleDC(dc) return; m_DCRect.SetRect(rect-left, rect-top, rect-right, rect-bottom); if (!m_MemoryBmp.CreateCompatibleBitmap(dc, m_DCRect.Width(), m_DCRect.Height() return; m_MemoryDC.SelectObject(m_MemoryBmp);CMemoryDC:CMemoryDC(void) if (m_bAutoRender) Render(); if (m_MemoryDC.m_hDC!=NULL) m_MemoryDC.DeleteDC(); if (m_MemoryBmp.m_hObject!=NULL) m_MemoryBmp.DeleteObject();bool CMemoryDC:IsOK() return m_MemoryDC.m_hDC!=NULL & m_MemoryBmp.m_hObject != NULL;void CMemoryDC:Render(CDC * p_objectDC) if (!IsOK() return; CDC * pDC = (p_objectDC=NULL ? m_pOriginalDC : p_objectDC); CSize Size = m_MemoryDC.GetViewportExt() ; pDC-BitBlt( m_DCRect.left, m_DCRect.top, m_DCRect.Width(), m_DCRect.Height(), &m_MemoryDC, 0,0, SRCCOPY);CDC* CMemoryDC:GetMemoryDC() return & m_MemoryDC;CMemoryDC:operator CDC * () return & m_MemoryDC;使用这个类可以大大简化内存DC的创建操作。如果我们在窗口消息WM_PAINT的响应函数中使用内存DC，只要用如下这样简便的代码便可实现：CRect Rect;GetClientRect(Rect);CPaintDC dc(this); / device context for painting CMemoryDC MemDC(&dc, Rect, true); if (MemDC.IsOK() / 使用MemDC画窗口