屏幕保护程序的退出机制反映在程序的消息响应函数（Window’s Procedure）中，当按下键盘上任何一个健或者鼠标移动计数超过5次（防止桌面振动等因素导致的鼠标移动），程序进入退出机制，在sm_test或者sm­­_full情况下查看屏幕保护程序是否设置密码，如果是，验证密码，正确，程序退出，错误，程序继续。当程序验证密码时，通过全局变量g_bCheckingSaverPassword告诉消息响应函数对屏幕刷新，以保证密码的输入。其他情况（sm_config, sm_preview）不用验证密码直接退出。这些功能包括在自定义的函数InterruptSaver( )和ShutdownSaver( )中。

上述各个函数的详细代码如下：

1、 CreateSaverWindow 函数：

HWND CreateSaverWindow(SaverMode mode, HWND hWndParent,HINSTANCE hInstance)
{
    HWND hWnd;
    RECT rc;
    DWORD dwStyle;

                           hWnd=NULL;
                          
    switch ( mode )
    {
        case sm_preview:
            GetClientRect(hWndParent, &rc );
            dwStyle = WS_VISIBLE | WS_CHILD;
            AdjustWindowRect( &rc, dwStyle, FALSE );
            hWnd = CreateWindow( TEXT("SaverWndClass"), TEXT("SaverWindow"), dwStyle,
                                    rc.left, rc.top, rc.right-rc.left, rc.bottom-rc.top,
                                    hWndParent, NULL, hInstance, NULL);
            break;

        case sm_test:
            rc.left = rc.top = 50;
            rc.right = rc.left+600;
            rc.bottom = rc.top+400;
            dwStyle = WS_VISIBLE | WS_OVERLAPPED | WS_CAPTION | WS_MINIMIZEBOX | WS_SYSMENU;
            AdjustWindowRect( &rc, dwStyle, FALSE );
            hWnd = CreateWindow( TEXT("SaverWndClass"), TEXT("SaverWindow"), dwStyle,
                                   rc.left, rc.top, rc.right-rc.left, rc.bottom-rc.top,
                                   NULL, NULL, hInstance, NULL);
            break;

        case sm_full:
           
            rc.left=rc.top=0;
                                     rc.bottom=GetSystemMetrics(SM_CYSCREEN);
                                     rc.right=GetSystemMetrics(SM_CXSCREEN);
                                     dwStyle = WS_VISIBLE | WS_POPUP;

            hWnd = CreateWindowEx( WS_EX_TOPMOST, TEXT("SaverWndClass"),
                    TEXT("SaverWindow"), dwStyle, rc.left, rc.top, rc.right - rc.left,
                    rc.bottom - rc.top, NULL, NULL, hInstance, NULL);
               
    }

    if(mode == sm_preview )
    {
        // 开始预览时，进入一个短暂的循环以使系统显示控制面板有足够的时间初始化
        g_bWaitForInputIdle = TRUE;
        // 开始循环
        PostMessage( g_hWnd, WM_USER, 0, 0 );

        MSG msg;

        while( g_bWaitForInputIdle )
        {
            // 如果If 返回 FALSE, 结束循环
            if( !GetMessage( &msg, g_hWnd, 0, 0 ) )
            {
                // 结束循环
                PostQuitMessage(0);
                break;
            }

            TranslateMessage( &msg);
            DispatchMessage( &msg);
        }
    }
   

    return hWnd;
}

2、 Window消息响应函数：

LRESULT CALLBACK SaverProc( HWND hWnd, UINT uMsg, WPARAM wParam, LPARAM lParam )
{
    switch ( uMsg )
        {
        case WM_USER:
            //预览开始循环，500ms空闲时间用于控制面板的初始化。
            SetTimer( hWnd, 1, 500, NULL );
            break;

        case WM_TIMER:
            // 500ms时间到，预览循环结束。
            g_bWaitForInputIdle = FALSE;
            KillTimer( hWnd, 1 );
            break;

        case WM_DESTROY:
            ShutdownSaver();
            break;

        case WM_SETCURSOR:
            if ( g_SaverMode == sm_full && !g_bCheckingSaverPassword )
            {
                //隐藏鼠标指针
                SetCursor( NULL );
                return TRUE;
            }
            break;

        case WM_PAINT:
        {
           
            PAINTSTRUCT ps;
            BeginPaint( hWnd, &ps );

                RECT rc;
                GetClientR

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