#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(dāng)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(biāo),iStrLen是這個列的長度
  int iStopTimes, iMustStopTimes; //已經(jīng)停滯的次數(shù)和必須停滯的次數(shù),必須停滯的次數(shù)是隨機的
}CharColumn, *pCharColumn;

int 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 ;
  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(biāo)光標(biāo)

  srand ((int) GetCurrentTime ()) ; //初始化隨機數(shù)發(fā)生器
  while (GetMessage (&msg, NULL, 0, 0))

{
   TranslateMessage (&msg) ;
   DispatchMessage (&msg) ;
  }
  ShowCursor(TRUE); //顯示鼠標(biāo)光標(biāo)
  return msg.wParam ;
}

TCHAR randomChar() //隨機字符產(chǎn)生函數(shù)
{
  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(biāo)
  cc->y =rand()%3?rand()%cyScreen:0; //顯示列的開始顯示的y坐標(biāo)
  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 = '';
    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 = '';
  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(nèi)存要用current當(dāng)參數(shù)
  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?zhǔn)欠?向下前進(jìn),如果等待次數(shù)超過必須等待的次數(shù),ctn就代表要向下前進(jìn)
  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(biāo),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(shù)
  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(shè)置背景模式為 透明
   iColumnCount = cxScreen/(iFontWidth*3/2); //屏幕所顯示字母雨的列數(shù)

   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(nèi)存設(shè)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(biāo) 為當(dāng)前的y坐標(biāo)加上 一個字符的高度
    //如果開始顯示的y坐標(biāo)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(dāng)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) ;
}