#include <windows.h> 

#define ID_TIMER    1 
#define STRMAXLEN  25 //一個顯示列的最大長度 
#define STRMINLEN  8  //一個顯示列的最小長度 

LRESULT CALLBACK WndProc(HWND, UINT, WPARAM, LPARAM);
// 
// 
typedef struct tagCharChain //整個當作屏幕的一個顯示列,這是個雙向列表 
{
    struct tagCharChain* prev; //鏈表的前個元素 
    TCHAR  ch;                  //一個顯示列中的一個字符 
    struct tagCharChain* next; //鏈表的后個元素 
}CharChain, * pCharChain;

typedef struct tagCharColumn
{
    CharChain* head, * current, * point;
    int x, y, iStrLen; //顯示列的開始顯示的x,y坐標,iStrLen是這個列的長度 
    int iStopTimes, iMustStopTimes; //已經停滯的次數和必須停滯的次數,必須停滯的次數是隨機的 
}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("此程序必須運行在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); //最大化顯示 
    UpdateWindow(hwnd);
    ShowCursor(FALSE); //隱藏鼠標光標 

    srand((int)GetCurrentTime()); //初始化隨機數發生器 
    while (GetMessage(&msg, NULL, 0, 0))
    {
        TranslateMessage(&msg);
        DispatchMessage(&msg);
    }
    ShowCursor(TRUE); //顯示鼠標光標 
    return msg.wParam;
}

TCHAR randomChar() //隨機字符產生函數 
{
    return (TCHAR)(rand() % (126 - 33)   33); //33到126之間 
}

int init(CharColumn* cc, int cyScreen, int x) //初始化 
{
    int j;
    cc->iStrLen = rand() % (STRMAXLEN - STRMINLEN)   STRMINLEN; //顯示列的長度 
    cc->x = x   3;        //顯示列的開始顯示的x坐標 
    cc->y = rand() % 3 ? rand() % cyScreen : 0; //顯示列的開始顯示的y坐標 
    cc->iMustStopTimes = rand() % 6;
    cc->iStopTimes = 0;
    cc->head = cc->current =
        (pCharChain)calloc(cc->iStrLen, sizeof(CharChain)); //生成顯示列 
    for (j = 0; j < cc->iStrLen - 1; j  )
    {
        cc->current->prev = cc->point; //cc->point一個顯示列的前個元素 
        cc->current->ch = '\0';
        cc->current->next = cc->current   1; //cc->current 1一個顯示列的后個元素 
        cc->point = cc->current  ; //cc->point = cc->current; cc->current  ; 
    }
    cc->current->prev = cc->point; //最后一個節點 
    cc->current->ch = '\0';
    cc->current->next = cc->head;
    cc->head->prev = cc->current; //頭節點的前一個為此鏈的最后一個元素 

    cc->current = cc->point = cc->head; //free掉申請的內存要用current當參數 
    cc->head->ch = randomChar(); // 對鏈表頭的 元素填充 
    return 0;
}

LRESULT CALLBACK WndProc(HWND hwnd, UINT message, WPARAM wParam, LPARAM lParam)
{
    HDC          hdc;
    //ctn 用來確定一個顯示鏈是否 向下前進,如果等待次數超過必須等待的次數,ctn就代表要向下前進 
    int i, j, temp, ctn; //j為一個顯示鏈中除鏈表頭外的在屏幕上顯示的y坐標,temp綠色過度到黑色之用 
    static  HDC hdcMem;
    HFONT    hFont;
    static  HBITMAP hBitmap;
    static  int cxScreen, cyScreen; //屏幕的寬度 高度. 
    static  int iFontWidth = 10, iFontHeight = 15, iColumnCount; //字體的寬度 高度, 列數 
    static  CharColumn* ccChain;

    switch (message)
    {
    case WM_CREATE:
        cxScreen = GetSystemMetrics(SM_CXSCREEN); //屏幕寬度 
        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);
        //創建字體 
        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); //設置背景模式為 透明 
        iColumnCount = cxScreen / (iFontWidth * 3 / 2); //屏幕所顯示字母雨的列數 

        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); //將內存設備映像刷成黑色 
        for (i = 0; i < iColumnCount; i  )
        {
            ctn = (ccChain   i)->iStopTimes   > (ccChain   i)->iMustStopTimes;
            // 
            (ccChain   i)->point = (ccChain   i)->head; //point用于遍歷整個顯示列 

            //第一個字符顯示為 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;
            //遍歷整個顯示列,將這個顯示列里的字符從下往上顯示 
            temp = 0; //temp綠色過度到黑色之用 
            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; //下次開始顯示的y坐標 為當前的y坐標加上 一個字符的高度 
            //如果開始顯示的y坐標減去 整個顯示列的長度超過了屏幕的高度 
            if ((ccChain   i)->y - (ccChain   i)->iStrLen * iFontHeight > cyScreen)
            {
                free((ccChain   i)->current);
                init(ccChain   i, cyScreen, (iFontWidth * 3 / 2) * i);
            }
            //鏈表的頭 為此鏈表的前個元素,因為下次開始顯示的時候 就相當與在整個顯示列的開頭添加個元素,然后在開始往上顯示 
            (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;

        //處理善后工作 
    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);
}