memdc.h

//////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
// CMemDC - memory DC
//
// Author: Keith Rule, 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.
//				 - 14/7/99 Added optional clip rect parameter [jgh]
//
//				 - 06/06/08  Added option to copy screen on construction
//
#if !defined(AFX_CMemDC_H__F666A491_3847_11D3_A58E_00805FC1DE10__INCLUDED_)
#define AFX_CMemDC_H__F666A491_3847_11D3_A58E_00805FC1DE10__INCLUDED_

class CMemDCEx : 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:
	/////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////// Function Header
	CMemDCEx(CDC* pDC, CRect rect = CRect(0,0,0,0), BOOL bCopyFirst = FALSE) : 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);
			if ( rect == CRect(0,0,0,0) )
				pDC->GetClipBox(&m_rect);
			else
				m_rect = rect;

			m_bitmap.CreateCompatibleBitmap(pDC, m_rect.Width(), m_rect.Height());
			m_oldBitmap = SelectObject(&m_bitmap);
			SetWindowOrg(m_rect.left, m_rect.top);
			if(bCopyFirst)
			{
				this->BitBlt(m_rect.left, m_rect.top, m_rect.Width(), m_rect.Height(),
					m_pDC, m_rect.left, m_rect.top, SRCCOPY);
			}
		} 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;
		}
	}

	/////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////// Function Header
	~CMemDCEx()
		//////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
	{
		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
	CMemDCEx* operator->() {return this;}

	// Allow usage as a pointer
	operator CMemDCEx*() {return this;}
};

#endif
// End CMemDC
//////////////////////////////////////////////////////////////////////////////////////////////////////////////////////