我建立了一个对话框工程,在OnPaint()中绘图,但是图像闪烁,所以想使用CMemDC类避免闪烁,我在网上抄了下面的代码,但是不知道用,请使用过的指点一下.
#ifndef _MEMDC_H_
#define _MEMDC_H_//////////////////////////////////////////////////
// CMemDC - memory DC
//
// Author: Keith Rule
// Email: [email protected]
// Copyright 1996-2002, 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
//
// 02/11/02 Added support for CScrollView as supplied
// by Gary Kirkham. - KR
//
// This class implements a memory Device Context which allows
// flicker free drawing.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, const CRect* pRect = NULL) : CDC()
{
ASSERT(pDC != NULL); // Some initialization
m_pDC = pDC;
m_oldBitmap = NULL;
m_bMemDC = !pDC->IsPrinting();// Get the rectangle to draw
if (pRect == NULL) {
pDC->GetClipBox(&m_rect);
} else {
m_rect = *pRect;
}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());SetWindowExt(pDC->GetWindowExt());
SetViewportExt(pDC->GetViewportExt());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());
}~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 accidentally 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
#ifndef _MEMDC_H_
#define _MEMDC_H_//////////////////////////////////////////////////
// CMemDC - memory DC
//
// Author: Keith Rule
// Email: [email protected]
// Copyright 1996-2002, 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
//
// 02/11/02 Added support for CScrollView as supplied
// by Gary Kirkham. - KR
//
// This class implements a memory Device Context which allows
// flicker free drawing.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, const CRect* pRect = NULL) : CDC()
{
ASSERT(pDC != NULL); // Some initialization
m_pDC = pDC;
m_oldBitmap = NULL;
m_bMemDC = !pDC->IsPrinting();// Get the rectangle to draw
if (pRect == NULL) {
pDC->GetClipBox(&m_rect);
} else {
m_rect = *pRect;
}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());SetWindowExt(pDC->GetWindowExt());
SetViewportExt(pDC->GetViewportExt());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());
}~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 accidentally 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
HDC dc = 对话框DC;
RECT rc;//对话框rc
::GetClientRect(this->m_hWnd,&rc); HDC hMemDC = ::CreateCompatibleDC(dc);//建立内存dc
HBITMAP hMemBitMap=::CreateCompatibleBitmap( dc, rc.right-rc.left , rc.bottom-rc.top );
::SelectObject(hMemDC , hMemBitMap); //下面在hMemDC上尽情的画你想画的
// 画啊画.......
//完事之后:
::BitBlt(dc ,rc.left, rc.top, rc.right-rc.left ,rc.bottom-rc.top ,hMemDC, rc.left, rc.top, SRCCOPY); ::DeleteObject(hMemBitMap);
::DeleteDC(hMemDC);
CSize pos = GetScrollPos(SB_HORZ);
pDC->MoveTo(-pos.cx +rect.left+60,rect.bottom-100);
pDC->LineTo(-pos.cx +rect.right-60,rect.bottom-100);
pDC->MoveTo(rect.left+60,rect.bottom-100);pDC->LineTo(rect.left+60,0)