用双缓存绘制方法减少绘图时的闪屏

CClientDC dc(this);

CRect rClient;
GetClientRect(&rClient);

CBitmap MemBmp;
MemBmp.CreateCompatibleBitmap(&dc, rClient.Width(), rClient.Height());

CDC MemDC;
MemDC.CreateCompatibleDC(NULL);
CBitmap* pOldMemBmp = MemDC.SelectObject(&MemBmp);

CDC bmpDC;
bmpDC.CreateCompatibleDC(&dc);

CBitmap* pOldBitmap = bmpDC.SelectObject(CBitmap::FromHandle(m_hBgBmp));
MemDC.BitBlt(rClient.left, rClient.top, m_SizeBg.cx, m_SizeBg.cy, &bmpDC, 0, 0, SRCCOPY);
bmpDC.SelectObject(pOldBitmap);
pOldBitmap = NULL;

CString sText = "……";
CFont font;
LOGFONT lf;
memset(&lf, 0, sizeof(LOGFONT));
lf.lfHeight = 14;
lf.lfWeight = FW_BOLD;
strcpy_s(lf.lfFaceName, LF_FACESIZE, "宋体");
font.CreateFontIndirect(&lf);
CFont* pOldFont = MemDC.SelectObject(&font);
MemDC.SetBkMode(TRANSPARENT);
MemDC.SetTextColor(RGB(255, 255, 255));
MemDC.TextOut(12, 8, sText);
MemDC.SelectObject(pOldFont);
font.DeleteObject();
DeleteDC(bmpDC);

dc.BitBlt(rClient.left, rClient.top, rClient.Width(), rClient.Height(), &MemDC, 0, 0, SRCCOPY);

MemDC.SelectObject(pOldMemBmp);
MemDC.DeleteDC();
MemBmp.DeleteObject();