问个窗口类的问题
WNDCLAS wndclass ;
wndclass.style = CS_HREDRAW | CS_VREDRAW ;
wndclass.lpfnWndProc = WndProc ;
wndclass.cbClsExtra = 0 ;
wndclass.cbWndExtra = 0 ;
wndclass.hInstance = hInstance ;
wndclass.hIcon = LoadIcon (NULL, IDI_APPLICATION) ;
wndclass.hCursor = LoadCursor (NULL, IDC_ARROW) ;
wndclass.hbrBackground = (HBRUSH) GetStockObject (WHITE_BRUSH) ;
wndclass.lpszMenuNam = NULL ;
wndclass.lpszClassName = szAppName ;
为什么窗口类要包含注册该类的实例的句柄,一个程序注册的窗口类是不是只有该程序才能在CreateWindow函数中使用?