MFC 双缓冲 如何解决背景不透明的问题？？？

[bazzi2011]

目前要解决一个控件闪烁问题，在OnTimer中刷新时间，显示在对话框中，由于有闪烁问题，所以采用双缓冲技术实现，可是由于我的对话框是贴图的，而又不知道该如何把画刷设置成透明色，所以效果如下：



黑色条目，时间区域是白色背景，由于我的对话框有背景图，所以我不知道该怎么创建一把透明的画刷？？？求教大神！！！

代码如下：

void CDlgXXX::OnTimer(UINT_PTR nIDEvent)
{
	if ( nIDEvent == Timer_ShowTime )
	{   
		int second = nCurrentTime % 60;
		int minute = nCurrentTime / 60 % 60;
		int hour = nCurrentTime / 60 / 60;
		sprintf(str,"%.2d:%.2d:%.2d",hour,minute,second); 

		GetDlgItem(IDC_EDIT_TIME)->SetWindowText(str);
		CRect rc;
		GetDlgItem(IDC_EDIT_TIME)->GetWindowRect(&rc);
		ScreenToClient(&rc);

		{
			HDC hTestViewDC = ::GetDC(this->m_hWnd);
			HDC hMemDC = ::CreateCompatibleDC(hTestViewDC);  //创建内存兼容DC
			//创建兼容位图
			HBITMAP hMemBmp = ::CreateCompatibleBitmap(hTestViewDC, rc.right-rc.left, rc.bottom-rc.top);
			HGDIOBJ hOldDC = ::SelectObject(hMemDC,hMemBmp);
			HBRUSH hBrush = CreateSolidBrush(0x00FFFFFF);//创建一把颜色刷子
			FillRect(hMemDC, &rc, hBrush);//填充View的背景颜色
			DeleteObject(hBrush);
 
			::TextOut(hMemDC, 11, 1, str, 8); //向内存DC画出东西
			::BitBlt(hTestViewDC,rc.left, rc.top,rc.right-rc.left, rc.bottom-rc.top,
				hMemDC, 0, 0, SRCCOPY); //拷贝位图到View上

			::SelectObject(hMemDC, hOldDC);
			::DeleteObject(hMemBmp);
			::DeleteDC(hMemDC);
			::ReleaseDC(this->m_hWnd, hTestViewDC);
                 }

[木黑神]

这不是Win32代码吗？ HBRUSH hbrush = CreateSolidBrush((HBRUSH)GetStockObject(NULL_BRUSH));//透明画刷

[xiaohuh421]

双缓冲是没有办法自动透明到背景的, 没有技术能实现得. 唯一的办法是扣背景. 你去看下主流的开源UI库, 都是这么做的. 透明,实际都是把父[窗口的背景对应区域复制一份贴到当前控件中.

[schlafenhamster]

CBrush* CDrawEditDlg::CreateBackgroundBrush(CDC* pDC,int ctrlId)
{
	CDC dcMem;
	dcMem.CreateCompatibleDC(pDC);//DeleteDC needed
	CBitmap* pOldBitmap = dcMem.SelectObject(&m_bitmap);
// Retrieve the size of our bitmap...
	BITMAP bmp;
	m_bitmap.GetObject(sizeof(bmp),&bmp);
// and the size of our dlg's client area
	CRect rect;
	GetClientRect(&rect);
//
	CRgn  rgnClip;
	CRect rc;
	GetDlgItem(ctrlId)->GetWindowRect(&rc);
	rgnClip.CreateRectRgnIndirect(rc);//DeleteObject needed
	CDC* pDCex=GetDCEx(&rgnClip,DCX_PARENTCLIP);//ReleaseDC needed
// Fill the client area of dlg,include the ctrl with our bitmap
	pDCex->StretchBlt(rect.left, rect.top,rect.Width(), rect.Height(),
					&dcMem,0, 0, bmp.bmWidth, bmp.bmHeight,SRCCOPY);
// we create the background brush of SelEdit
	CDC dcMemCtrl;
	dcMemCtrl.CreateCompatibleDC(pDCex);//DeleteDC needed
	CBitmap CtrlBmp;//DeleteObject needed
	CtrlBmp.CreateCompatibleBitmap(pDCex,rc.Width(),rc.Height());
	pOldBitmap = dcMemCtrl.SelectObject(&CtrlBmp);
	ScreenToClient(&rc);
	MapWindowPoints(this,rc);
//	afxDump << rc << " xx\n";
	dcMemCtrl.BitBlt(0, 0, rc.Width(), rc.Height(), pDCex, rc.left, rc.top, SRCCOPY);
	CBitmap  *nowBMP=dcMemCtrl.SelectObject(pOldBitmap); 
// copy to CB for checking
#ifdef TEST
	OpenClipboard();
	EmptyClipboard(); 
	SetClipboardData(CF_BITMAP,nowBMP->GetSafeHandle());
	CloseClipboard();
#endif
	CBrush *pBackBr=new CBrush;
	pBackBr->CreatePatternBrush(nowBMP);
//
	DeleteObject(rgnClip);
	DeleteObject(CtrlBmp);
	ReleaseDC(pDCex);
	dcMemCtrl.DeleteDC();
//
	return pBackBr;
}

初始化 BOOL CxxxxDlg::OnEraseBkgnd(CDC* pDC) { // TODO: Add your message handler code here and/or call default // Create Edit background brush; only once ! if(!m_bInitEditBr) {// add edit rect m_bInitEditBr=TRUE; m_pbrEd=CreateBackgroundBrush(pDC, IDC_SEL_EDIT); }