C++实现数字雨效果的方法是什么

#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()%2+48); //字符0或1
} 
 
int init(CharColumn *cc, int cyScreen, int x) //初始化 
{ 
    int j; 
    cc->iStrLen = rand()%(STRMAXLEN-STRMINLEN) + STRMINLEN; //显示列的长度 
    cc->x = x+3 ;    //显示列的开始显示的x坐标 
    cc->y =rand()%3&#63;rand()%cyScreen:0; //显示列的开始显示的y坐标 
    cc->iMustStopTimes = rand()%6 ; 
    cc->iStopTimes  = 0 ; 
    cc->head = cc->current = 
        (pCharChain)calloc(cc->iStrLen, sizeof(CharChain)); //生成显示列 
    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 = '\0'; 
        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 = '\0'; 
    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 ; 
    //ctn 用来确定一个显示链是否 向下前进,如果等待次数超过必须等待的次数,ctn就代表要向下前进 
    int i, j, temp, ctn; //j为一个显示链中除链表头外的在屏幕上显示的y坐标,temp绿色过度到黑色之用 
    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*3/2); //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 白色 
            SetTextColor(hdcMem, RGB(255, 255, 255)); 
            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) ; 
}