Style Toolkit - Use advanced graphics techniques to create a custom user interface

//
// MemDC.h : Version 1.0 
//
// Author:  Darren Sessions
//          
//
// Description:
//      MemDC is a memory DC class based on the one written by Keith Rule.  The primary 
//		difference is the copy first option and the storage option.  Copy first should be set 
//		to true when working with objects that have transparency.  The storage type DC is 
//		defined but not created until the Create function is called.  The storage type does
//		not attempt to copy anything on destruction.
//
// History
//     Version 1.0 - 2008 June 20
//     - Initial public release
//
// License:
//     This software is released under the Code Project Open License (CPOL),
//     which may be found here:  http://www.codeproject.com/info/eula.aspx
//     You are free to use this software in any way you like, except that you 
//     may not sell this source code.
//
//     This software is provided "as is" with no expressed or implied warranty.
//     I accept no liability for any damage or loss of business that this 
//     software may cause.
//
///////////////////////////////////////////////////////////////////////////////

#pragma once

#define ENABLE_GDIP_FUNTION

class MemDC : public CDC 
{

private:
	CDC*		m_pDC;			// CDC of passed in constructor
	CRect		m_rect;			// Rectangle of drawing area.
	BOOL		m_bPrintDC;		// True if printing
	BOOL		m_bCopyFirst;	// Copy existing on construction
	BOOL		m_bStorageDC;	// True if used for storing a bitmap
	CBitmap*	m_pOld;			// passed DC's bitmap
	CBitmap		m_bitmap;		// Offscreen bitmap
	BOOL		m_bCreated;		// TRUE after creation

public:

	// default constructor - requires subsequent create call
	MemDC() { m_bStorageDC = TRUE; m_bPrintDC = FALSE; m_bCreated = FALSE; };

	// constructor 
	MemDC(CDC* pDC, CRect rect, BOOL bCopyFirst = FALSE) 
		: CDC(), m_pDC(pDC), m_rect(rect), m_bCopyFirst(bCopyFirst)
	{
		// NULL dc not allowed
		ASSERT(m_pDC != NULL); 
		m_bStorageDC = FALSE;
		Init();
	}

	// create a MemDC and copy the data
	void Create(CDC* pDC, CRect rect)
	{
		// NULL dc not allowed
		ASSERT(pDC != NULL); 
		m_pDC = pDC;
		m_rect = rect;
		m_bCopyFirst = TRUE;
		m_bStorageDC = TRUE;

		Init();
	}
	
	void Init()
	{
		// true if printing
		m_bPrintDC = m_pDC->IsPrinting();
		
		if(!m_bPrintDC)
		{
			// Create a compatible DC
			CreateCompatibleDC(m_pDC);

			// create a compatible bitmap
			m_bitmap.CreateCompatibleBitmap(m_pDC, m_rect.Width(), m_rect.Height());

			// select bitmap into dc
			m_pOld = SelectObject(&m_bitmap);

			// set window origin
			SetWindowOrg(m_rect.left, m_rect.top);	

			// needed for transparency support
			if(m_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 = m_pDC->m_bPrinting;
			m_hAttribDC = m_pDC->m_hAttribDC;
			m_hDC		= m_pDC->m_hDC;
		}

		m_bCreated = TRUE;
	}
	
#ifdef ENABLE_GDIP_FUNTION
	Bitmap* GetBitmap() {	CPalette* pPalette = m_pDC->GetCurrentPalette();
							return	Bitmap::FromHBITMAP((HBITMAP)m_bitmap.GetSafeHandle(), 
									(HPALETTE)pPalette->GetSafeHandle()); 
						}
#endif

	// destructor
	~MemDC()
	{
		if(!m_bPrintDC && !m_bStorageDC) 
		{
			// 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_pOld);
		} 
		else if(m_bPrintDC)
		{
			// 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;
		}
	}

	// pointer operators
	MemDC* operator->()	{ return this; }
	operator MemDC*()		{ return this; }
};