case WM_LBUTTONDOWN：   {    SHRGINFO shrg;    shrg.cbSize = sizeof(shrg);    shrg.hwndClient = m_hWnd;    shrg.ptDown.x = LOWORD(lParam);    shrg.ptDown.y = HIWORD(lParam);    shrg.dwFlags = SHRG_RETURNCMD;    CPoint point;    point.x = shrg.ptDown.x;    point.y = shrg.ptDown.y;    if(::SHRecognizeGesture(&shrg) == GN_CONTEXTMENU)//长按键消息       {        CMenu menu;        menu.LoadMenu(IDR_MENU_DOWN);        CMenu *pPopupMenu = menu.GetSubMenu(0);               ClientToScreen(&point);        pPopupMenu->TrackPopupMenu(TPM_LEFTALIGN,point.x,point.y,this);       } }