[MFC] MemDC 코드, 펌자료입니다. ^^

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#ifndef _MEMDC_H_
#define _MEMDC_H_

//////////////////////////////////////////////////
// CMemDC - memory DC
//
// Author: Keith Rule
// Email:  keithr@europa.com
// Copyright 1996-1999, 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. - KR
//
//           11/3/99 Fixed most common complaint. Added
//                   background color fill. - KR
//
//           11/3/99 Added support for mapping modes other than
//                   MM_TEXT as suggested by Lee Sang Hun. - KR
//
// This class implements a memory Device Context which allows
// flicker free drawing.

class CMemDC : public CDC {
protected:
 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.

 void Construct(CDC* pDC)
 {
  ASSERT(pDC != NULL);

  // Some initialization
  m_pDC = pDC;
  m_oldBitmap = NULL;
  m_bMemDC = !pDC->IsPrinting();

  if (m_bMemDC) {
   // Create a Memory DC
   CreateCompatibleDC(pDC);
   pDC->LPtoDP(&m_rect);

   m_bitmap.CreateCompatibleBitmap(pDC, m_rect.Width(), m_rect.Height());
   m_oldBitmap = SelectObject(&m_bitmap);

   SetMapMode(pDC->GetMapMode());
   pDC->DPtoLP(&m_rect);
   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;
  }

  // Fill background
  FillSolidRect(m_rect, pDC->GetBkColor());
 }

 // TRK begin
public:
 CMemDC(CDC* pDC                  ) : CDC() { pDC->GetClipBox(&m_rect); Construct(pDC); }
 CMemDC(CDC* pDC, const RECT& rect) : CDC() { m_rect = rect           ; Construct(pDC); }
 // TRK end

 virtual ~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