谁能帮我讲解一下这个函数内容（Hook知识不用说了），非常感谢

//定义钩子函数，对按钮控件子类化
LRESULT CALLBACK HOOKProc( int nCode, WPARAM wParam, LPARAM lParam )
{
PCWPSTRUCT wc = (PCWPSTRUCT) lParam;
HWND hWnd = wc->hwnd;
if( hWnd )
{
char ClassName[MAX_PATH] = "";
GetClassName( hWnd, ClassName, MAX_PATH );
if( strcmp( ClassName, "Button" ) == 0 )
{
CWnd *pWnd = CWnd::FromHandle( hWnd );

        if ( pWnd->GetStyle() & BS_RADIOBUTTON )
        {
            return 1;
        }
        if ( pWnd->GetStyle() & BS_CHECKBOX )
        {
            return 1;
        }

        WNDPROC WndProc;
        WndProc = (WNDPROC) GetWindowLong( hWnd, GWL_WNDPROC );

        CDrawButton *pButton=(CDrawButton*)GetWindowLong(hWnd,GWL_USERDATA);

        if (pButton != NULL&& pButton->m_Flag==1 )
        {
            SetWindowLong(hWnd,GWL_USERDATA,0);
            SetWindowLong( hWnd, GWL_WNDPROC, (LONG)pButton->m_OldProc );

            pButton->m_OldProc = NULL;
            delete pButton;
        }
        else if (pButton == NULL ) 
        {
            if( WndProc !=DefWindowProc1 )
            {
                pButton = new CDrawButton;
                pButton->m_OldProc = WndProc;
                SetWindowLong(hWnd,GWL_USERDATA,(long)pButton);
                WndProc =  (WNDPROC) SetWindowLong( hWnd, GWL_WNDPROC, (LONG) DefWindowProc1);
            }
        }
    }
}
return CallNextHookEx( hWndHook, nCode, wParam, lParam );

}

WNDPROC WndProc;
WndProc = (WNDPROC) GetWindowLong( hWnd, GWL_WNDPROC );
这个是获取hWnd的窗口处理过程，GWL_USERDATA这是获取当前hWnd的用户数据。
else if (pButton == NULL )
{
if( WndProc !=DefWindowProc1 )//这是一个新的窗口处理过程函数地址
{
pButton = new CDrawButton;
pButton->m_OldProc = WndProc;
SetWindowLong(hWnd,GWL_USERDATA,(long)pButton);
WndProc = (WNDPROC) SetWindowLong( hWnd, GWL_WNDPROC, (LONG) DefWindowProc1);
}
}