MSDN上说，在DLL中注册的窗口类在DLL卸载时不会自动反注册，我们程序必须保证在DLL卸载时，将所有在DLL中注册的窗口类反注册掉（原文：Windows NT/2000 or later: No window classes registered by a .dll are unregistered when the .dll is unloaded. A .dll must explicitly unregister its classes when it is unloaded. ）。
LPCTSTR AFXAPI AfxRegisterWndClass(UINT nClassStyle,
HCURSOR hCursor, HBRUSH hbrBackground, HICON hIcon)
{
// Returns a temporary string name for the class
// Save in a CString if you want to use it for a long time
LPTSTR lpszName = AfxGetThreadState()->m_szTempClassName;
// generate a synthetic name for this class
HINSTANCE hInst = AfxGetInstanceHandle();
if (hCursor == NULL && hbrBackground == NULL && hIcon == NULL)
wsprintf(lpszName, _T("Afx:%x:%x"), (UINT)hInst, nClassStyle);
else
wsprintf(lpszName, _T("Afx:%x:%x:%x:%x:%x"), (UINT)hInst, nClassStyle,
(UINT)hCursor, (UINT)hbrBackground, (UINT)hIcon);
// see if the class already exists
WNDCLASS wndcls;
if (::GetClassInfo(hInst, lpszName, &wndcls))
{
// already registered, assert everything is good
ASSERT(wndcls.style == nClassStyle);
// NOTE: We have to trust that the hIcon, hbrBackground, and the
// hCursor are semantically the same, because sometimes Windows does
// some internal translation or copying of those handles before
// storing them in the internal WNDCLASS retrieved by GetClassInfo.
return lpszName;
}
// otherwise we need to register a new class
wndcls.style = nClassStyle;
wndcls.lpfnWndProc = DefWindowProc;
wndcls.cbClsExtra = wndcls.cbWndExtra = 0;
wndcls.hInstance = hInst;
wndcls.hIcon = hIcon;
wndcls.hCursor = hCursor;
wndcls.hbrBackground = hbrBackground;
wndcls.lpszMenuName = NULL;
wndcls.lpszClassName = lpszName;
if (!AfxRegisterClass(&wndcls))
AfxThrowResourceException();
// return thread-local pointer
return lpszName;
}
// like RegisterClass, except will automatically call UnregisterClass
BOOL AFXAPI AfxRegisterClass(WNDCLASS* lpWndClass)
{
WNDCLASS wndcls;
if (GetClassInfo(lpWndClass->hInstance, lpWndClass->lpszClassName,
&wndcls))
{
// class already registered
return TRUE;
}
if (!::RegisterClass(lpWndClass))
{
TRACE1("Can't register window class named %s\n",
lpWndClass->lpszClassName);
return FALSE;
}
if (afxContextIsDLL)
{
AfxLockGlobals(CRIT_REGCLASSLIST);
TRY
{
// class registered successfully, add to registered list
AFX_MODULE_STATE* pModuleState = AfxGetModuleState();
LPTSTR lpszUnregisterList = pModuleState->m_szUnregisterList;
// the buffer is of fixed size -- ensure that it does not overflow
ASSERT(lstrlen(lpszUnregisterList) + 1 +
lstrlen(lpWndClass->lpszClassName) + 1 <
_countof(pModuleState->m_szUnregisterList));
// append classname + newline to m_szUnregisterList
lstrcat(lpszUnregisterList, lpWndClass->lpszClassName);
TCHAR szTemp[2];
szTemp[0] = '\n';
szTemp[1] = '\0';
lstrcat(lpszUnregisterList, szTemp);
}
CATCH_ALL(e)
{
AfxUnlockGlobals(CRIT_REGCLASSLIST);
THROW_LAST();
// Note: DELETE_EXCEPTION not required.
}
END_CATCH_ALL
AfxUnlockGlobals(CRIT_REGCLASSLIST);
}
