怎样在MM_LOMETRIC 模式下，实现双缓存

Question

在MM_LOMETRIC 下用双缓存，屏幕显示一堆乱七八糟的动写，怎样才能让图形能够正确显示出来呢？

Answer 1

我用的就是MM_LOMETRIC 下的双缓存。你把你的代码写出来，我替你修改。

Answer 2

CPaintDC *dc =new CPaintDC(this);
int nWidth=800,nHeight=600;
CDC *pDC=new CDC;
CBitmap bmp;
pDC->CreateCompatibleDC(dc);
bmp.CreateCompatibleBitmap(dc,nWidth,nHeight);
CBitmap *pBmp=pDC->SelectObject(&bmp);
pDC->FillSolidRect(0,0,nWidth,nHeight,RGB(255,255,255));
pDC->SetMapMode(MM_LOMETRIC   );
pDC->MoveTo(0,0);
pDC->LineTo(100,-200);
//pDC->Rectangle(10,10,200,200);
dc->BitBlt(0,0,nWidth,nHeight,pDC,0,0,SRCCOPY);
pDC->SelectObject(pBmp);
我是在OnPaint() 中写的

Answer 3

大致应该这样，不便调试，如有问题，请发短信。CPaintDC dc(this);
CDC dcMem; 
CRect rect;
GetClientRect(rect);CBitmap memBitmap;
dc.SetMapMode(MM_LOMETRIC);
dcMem.CreateCompatibleDC(&dc);
dcMem.SetMapMode(MM_LOMETRIC);
memBitmap.CreateCompatibleBitmap(&dc, rect.Width(), rect.Height());
dc.DPtoLP(rect); CBitmap *pOldBit = dcMem.SelectObject(&memBitmap);
dcMem.FillSolidRect(rect, RGB(255, 255, 255));dcMem.MoveTo(0,0);
dcMem.LineTo(100,-200);dc.BitBlt(0, 0, rect.Width(), rect.Height(), &dcMem, 0, 0, SRCCOPY);
dcMem.SelectObject(pOldBit);

Answer 4

CPaintDC *dc =new CPaintDC(this);
int nWidth=800,nHeight=600;
CDC *pDC=new CDC;
CBitmap bmp;
pDC->CreateCompatibleDC(dc);
bmp.CreateCompatibleBitmap(dc,nWidth,nHeight);
CBitmap *pBmp=pDC->SelectObject(&bmp);
pDC->SetMapMode(MM_LOMETRIC   );
pDC->FillSolidRect(0,0,nWidth,-nHeight,RG(255,255,255));

pDC->MoveTo(0,0);
pDC->LineTo(100,-200);
//pDC->Rectangle(10,10,200,200);
pDC->SetMapMode(MM_TEXT  );
dc->BitBlt(0,0,nWidth,nHeight,pDC,0,0,SRCCOPY);
pDC->SelectObject(pBmp);
问题已解决，映射完后我又映射回来了，谢谢你给我提供了思路，我还想问一个问题，现在我的代码存在闪屏，可是我有从载不了OnEraseBkgnd(CDC* pDC)函数，能不能帮忙解决一下。