www.pudn.com > enh_flatbar_sample.zip > MemDC.h, change:1997-10-17,size:2135b


#ifndef _MEMDC_H_ 
#define _MEMDC_H_ 
 
////////////////////////////////////////////////// 
// CMemDC - memory DC 
// 
// Author: Keith Rule 
// Email:  keithr@europa.com 
// Copyright 1996-1997, Keith Rule 
// 
// You may freely use or modify this code provided this 
// Copyright is included in all derived versions. 
// 
// History - 10/3/97 Fixed scrolling bug. 
//                   Added print support. 
// 
// This class implements a memory Device Context 
 
class CMemDC : public CDC { 
private: 
	CBitmap m_bitmap;		// Offscreen bitmap 
	CBitmap* m_oldBitmap;	// bitmap originally found in CMemDC 
	CDC* m_pDC;				// Saves CDC passed in constructor 
	CRect m_rect;			// Rectangle of drawing area. 
	BOOL m_bMemDC;			// TRUE if CDC really is a Memory DC. 
 
public: 
	CMemDC(CDC* pDC) : CDC(), m_oldBitmap(NULL), m_pDC(pDC) 
	{ 
		ASSERT(m_pDC != NULL); // If you asserted here, you passed in a NULL CDC. 
                 
		m_bMemDC = !pDC->IsPrinting(); 
                 
		if (m_bMemDC){ 
			// Create a Memory DC 
			CreateCompatibleDC(pDC); 
			pDC->GetClipBox(&m_rect); 
			m_bitmap.CreateCompatibleBitmap(pDC, m_rect.Width(), m_rect.Height()); 
			m_oldBitmap = SelectObject(&m_bitmap); 
			SetWindowOrg(m_rect.left, m_rect.top); 
		} else { 
			// Make a copy of the relevent parts of the current DC for printing 
			m_bPrinting = pDC->m_bPrinting; 
			m_hDC = pDC->m_hDC; 
			m_hAttribDC = pDC->m_hAttribDC; 
		} 
	} 
         
	~CMemDC() 
	{ 
		if (m_bMemDC) { 
			// Copy the offscreen bitmap onto the screen. 
			m_pDC->BitBlt(m_rect.left, m_rect.top, m_rect.Width(), m_rect.Height(), 
							this, m_rect.left, m_rect.top, SRCCOPY); 
			//Swap back the original bitmap. 
			SelectObject(m_oldBitmap); 
		} else { 
			// All we need to do is replace the DC with an illegal value, 
			// this keeps us from accidently deleting the handles associated with 
			// the CDC that was passed to the constructor. 
			m_hDC = m_hAttribDC = NULL; 
		} 
	} 
         
	// Allow usage as a pointer 
	CMemDC* operator->() {return this;} 
         
	// Allow usage as a pointer 
	operator CMemDC*() {return this;} 
}; 
 
#endif