判断指定窗口是否被其他窗口遮挡

转载：https://www.cnblogs.com/findumars/p/5086797.html

bool CTestTray2Dlg::IsCoveredByOtherWindow(HWND hWnd)
{
 RECT rcTarget; 
 ::GetWindowRect(hWnd, &rcTarget);

 bool isChild = (WS_CHILD == (::GetWindowLong(hWnd, GWL_STYLE) & WS_CHILD));

 if (::GetDesktopWindow() == hWnd)
  hWnd = ::GetWindow(::GetTopWindow(hWnd), GW_HWNDLAST);

 do{ 
  HWND hCurWnd = hWnd;

  while(NULL != (hWnd = ::GetNextWindow(hWnd, GW_HWNDPREV))){ 
   if (::IsWindowVisible(hWnd)){ 
    RECT rcWnd; 
    ::GetWindowRect(hWnd, &rcWnd);

    if(!((rcWnd.right < rcTarget.left) || (rcWnd.left > rcTarget.right) || 
     (rcWnd.bottom < rcTarget.top) || (rcWnd.top > rcTarget.bottom))){ 
     return true; 
    } 
   } 
  }

  if(isChild){ 
   hWnd = ::GetParent(hCurWnd); 
   isChild = hWnd ? (WS_CHILD == (::GetWindowLong(hWnd, GWL_STYLE) & WS_CHILD)) : false; 
  } 
  else 
   break; 
 }while(true);

 return false;
}

大意是自底向上层层遍历窗口，检查是否有窗口与指定窗口有重叠的地方。