黑客帝国之酷炫屏保数字雨

本程序vs2013 测试通过，不排除其他测试通过用例，主要是windows API的应用

#include <windows.h> 

#define ID_TIMER    1 
#define STRMAXLEN  25 //一个显示列的最大长度 
#define STRMINLEN  8  //一个显示列的最小长度 

LRESULT CALLBACK WndProc(HWND, UINT, WPARAM, LPARAM);
////////////////////////////////////////////////////////////////// 
////////////////////////////////////////////////////////////////// 
typedef struct tagCharChain //整个当作屏幕的一个显示列,这是个双向列表 
{
    struct tagCharChain *prev; //链表的前个元素 
    TCHAR  ch;                  //一个显示列中的一个字符 
    struct tagCharChain *next; //链表的后个元素 
}CharChain, *pCharChain;

typedef struct tagCharColumn
{
    CharChain *head, *current, *point;
    int x, y, iStrLen; //显示列的开始显示的x,y坐标,iStrLen是这个列的长度 
    int iStopTimes, iMustStopTimes; //已经停滞的次数和必须停滞的次数,必须停滞的次数是随机的 
}CharColumn, *pCharColumn;

int main(HINSTANCE hInstance, HINSTANCE hPrevInstance,
                                    PSTR szCmdLine, int iCmdShow)
{
    static TCHAR szAppName[] = TEXT("matrix");
    HWND            hwnd;
    MSG            msg;
    WNDCLASS    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(BLACK_BRUSH);
    wndclass.lpszMenuName = NULL;
    wndclass.lpszClassName = szAppName;

    if (!RegisterClass(&wndclass))
    {
        MessageBox(NULL, TEXT("此程序必须运行在NT下!"), szAppName, MB_ICONERROR);
        return 0;
    }

    hwnd = CreateWindow(szAppName, NULL,
        WS_DLGFRAME | WS_THICKFRAME | WS_POPUP,
        0, 0,
        GetSystemMetrics(SM_CXSCREEN), GetSystemMetrics(SM_CYSCREEN),
        NULL, NULL, hInstance,
        NULL);

    ShowWindow(hwnd, SW_SHOWMAXIMIZED); //最大化显示 
    UpdateWindow(hwnd);
    ShowCursor(FALSE); //隐藏鼠标光标 

    srand((int)GetCurrentTime()); //初始化随机数发生器 
    while (GetMessage(&msg, NULL, 0, 0))
    {
        TranslateMessage(&msg);
        DispatchMessage(&msg);
    }
    ShowCursor(TRUE); //显示鼠标光标 
    return msg.wParam;
}

TCHAR randomChar() //随机字符产生函数 
{
    return (TCHAR)(rand() % (126 - 33) + 33); //33到126之间 
}

int init(CharColumn *cc, int cyScreen, int x) //初始化 
{
    int j;
    cc->iStrLen = rand() % (STRMAXLEN - STRMINLEN) + STRMINLEN; 
    cc->x = x + 3;      
    cc->y = rand() % 3 ? rand() % cyScreen : 0;
    cc->iStopTimes = 0;
    cc->head = cc->current =
        (pCharChain)calloc(cc->iStrLen, sizeof(CharChain)); 
    for (j = 0; j < cc->iStrLen - 1; j++)
    {
        cc->current->prev = cc->point; //cc->point一个显示列的前个元素 
        cc->current->ch = '';
        cc->current->next = cc->current + 1; //cc->current+1一个显示列的后个元素 
        cc->point = cc->current++; //cc->point = cc->current; cc->current++; 
    }
    cc->current->prev = cc->point; //最后一个节点 
    cc->current->ch = '';
    cc->current->next = cc->head;
    cc->head->prev = cc->current; //头节点的前一个为此链的最后一个元素 

    cc->current = cc->point = cc->head; //free掉申请的内存要用current当参数 
    cc->head->ch = randomChar(); // 对链表头的 元素填充 
    return 0;
}

LRESULT CALLBACK WndProc(HWND hwnd, UINT message, WPARAM wParam, LPARAM lParam)
{
    HDC          hdc;

    int i, j, temp, ctn; 
    static  HDC hdcMem;
    HFONT    hFont;
    static  HBITMAP hBitmap;
    static  int cxScreen, cyScreen; //屏幕的宽度 高度. 
    static  int iFontWidth = 10, iFontHeight = 15, iColumnCount; //字体的宽度 高度, 列数 
    static  CharColumn *ccChain;

    switch (message)
    {
    case WM_CREATE:
        cxScreen = GetSystemMetrics(SM_CXSCREEN); //屏幕宽度 
        cyScreen = GetSystemMetrics(SM_CYSCREEN);
        SetTimer(hwnd, ID_TIMER, 10, NULL);

        hdc = GetDC(hwnd);
        hdcMem = CreateCompatibleDC(hdc);
        hBitmap = CreateCompatibleBitmap(hdc, cxScreen, cyScreen);
        SelectObject(hdcMem, hBitmap);
        ReleaseDC(hwnd, hdc);
        //创建字体 
        hFont = CreateFont(iFontHeight, iFontWidth - 5, 0, 0, FW_BOLD, 0, 0, 0,
            DEFAULT_CHARSET, OUT_DEFAULT_PRECIS, CLIP_DEFAULT_PRECIS,
            DRAFT_QUALITY, FIXED_PITCH | FF_SWISS, TEXT("Fixedsys"));
        SelectObject(hdcMem, hFont);
        DeleteObject(hFont);
        SetBkMode(hdcMem, TRANSPARENT); //设置背景模式为 透明 
        iColumnCount = cxScreen / (iFontWidth * 1 / 2); //屏幕所显示字母雨的列数 

        ccChain = (pCharColumn)calloc(iColumnCount, sizeof(CharColumn));
        for (i = 0; i < iColumnCount; i++)
        {
            init(ccChain + i, cyScreen, (iFontWidth * 3 / 2)*i);
        }
        return 0;

    case WM_TIMER:
        hdc = GetDC(hwnd);
        PatBlt(hdcMem, 0, 0, cxScreen, cyScreen, BLACKNESS); //将内存设备映像刷成黑色 
        for (i = 0; i < iColumnCount; i++)
        {
            ctn = (ccChain + i)->iStopTimes++ > (ccChain + i)->iMustStopTimes;
            // 
            (ccChain + i)->point = (ccChain + i)->head; //point用于遍历整个显示列 

            //第一个字符显示为绿 
            SetTextColor(hdcMem, RGB(0, 255, 0));
            TextOut(hdcMem, (ccChain + i)->x, (ccChain + i)->y, &((ccChain + i)->point->ch), 1);
            j = (ccChain + i)->y;
            (ccChain + i)->point = (ccChain + i)->point->next;
            //遍历整个显示列,将这个显示列里的字符从下往上显示 
            temp = 0; //temp绿色过度到黑色之用 
            while ((ccChain + i)->point != (ccChain + i)->head && (ccChain + i)->point->ch)
            {
                SetTextColor(hdcMem, RGB(0, 255 - (255 * (temp++) / (ccChain + i)->iStrLen), 0));
                TextOut(hdcMem, (ccChain + i)->x, j -= iFontHeight, &((ccChain + i)->point->ch), 1);
                (ccChain + i)->point = (ccChain + i)->point->next;
            }
            if (ctn)
                (ccChain + i)->iStopTimes = 0;
            else continue;
            (ccChain + i)->y += iFontHeight; //下次开始显示的y坐标 为当前的y坐标加上 一个字符的高度 
            //如果开始显示的y坐标减去 整个显示列的长度超过了屏幕的高度 
            if ((ccChain + i)->y - (ccChain + i)->iStrLen*iFontHeight > cyScreen)
            {
                free((ccChain + i)->current);
                init(ccChain + i, cyScreen, (iFontWidth * 3 / 2)*i);
            }
            //链表的头 为此链表的前个元素,因为下次开始显示的时候 就相当与在整个显示列的开头添加个元素,然后在开始往上显示 
            (ccChain + i)->head = (ccChain + i)->head->prev;
            (ccChain + i)->head->ch = randomChar();
        }

        BitBlt(hdc, 0, 0, cxScreen, cyScreen, hdcMem, 0, 0, SRCCOPY);
        ReleaseDC(hwnd, hdc);
        return 0;

    case WM_RBUTTONDOWN:
        KillTimer(hwnd, ID_TIMER);
        return 0;

    case WM_RBUTTONUP:
        SetTimer(hwnd, ID_TIMER, 10, NULL);
        return 0;

        //处理善后工作 
    case WM_KEYDOWN:
    case WM_LBUTTONDOWN:
    case WM_DESTROY:
        KillTimer(hwnd, ID_TIMER);
        DeleteObject(hBitmap);
        DeleteDC(hdcMem);
        for (i = 0; i < iColumnCount; i++)
        {
            free((ccChain + i)->current);
        }
        free(ccChain);
        PostQuitMessage(0);
        return 0;
    }
    return DefWindowProc(hwnd, message, wParam, lParam);
}