#include <windows.h>
#include <windowsx.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 WINAPI WinMain(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 ; // class style
    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, // windows style
              0, 0,
              GetSystemMetrics(SM_CXSCREEN), GetSystemMetrics(SM_CYSCREEN),
              NULL, NULL, hInstance,
              NULL) ;

    ShowWindow (hwnd, SW_SHOWMAXIMIZED) ; //最大化顯示 show windows
    UpdateWindow (hwnd) ;
    ShowCursor(FALSE); //隱藏鼠標光標
    
    srand ((int) GetCurrentTime ()) ; //初始化隨機數發(fā)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(jié)點
    cc->current->ch = '\0';
    cc->current->next = cc->head;
    cc->head->prev  = cc->current; //頭節(jié)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(chuàng)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) ;
}