#include<windows.h>
#include<stdlib.h>
#include<string.h>
void WINAPI CaretPos(HWND hWnd,    int nArrayPos,char *cCharBuf,int *xCaret,int *yCaret,int nCharWidth);
long WINAPI WndProc(HWND hWnd,UINT iMessage,UINT wParam,LONG lParam);
BOOL InitWindowsClass(HINSTANCE hInstance);
BOOL InitWindows(HINSTANCE hInstance,int nCmdShow);
HWND hWndMain;

int WINAPI WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance, LPSTR lpCmdLine, int nCmdShow)
{ 
    MSG Message;
    if(!InitWindowsClass(hInstance)) return FALSE;
    if(!InitWindows(hInstance,nCmdShow))  return FALSE;
    while(GetMessage(&Message,0,0,0))//消息循環
    {
        TranslateMessage(&Message);
        DispatchMessage(&Message);
    }
    return Message.wParam;
}

//消息處理函數
long WINAPI WndProc(HWND hWnd,UINT iMessage,UINT wParam,LONG lParam)
{
  #define BufSize 30    //設置存放字符的緩沖區大小
  static char cCharBuf[BufSize];//設置靜態字符數組，
  static int nNumChar=0;//現有字符個數
  static int nArrayPos=0;//字符的位置
  static int nLnHeight;
  static int nCharWidth;
  static int xCaret,yCaret;
  int x;
  HDC hDC;
  TEXTMETRIC tm;
  PAINTSTRUCT PtStr; //定義指向包含繪圖信息的結構體變量

  switch(iMessage)      //處理消息
  {
   case WM_CHAR:          //遇到非系統字符所作的處理
       {
         if(wParam==VK_BACK)  //處理退格鍵的消息
         {
             if(nArrayPos==0)     //若已在一行文字的開始處，則提示用戶"不能回退"
               MessageBox(hWnd,"當前位置是文本的起始位置，不能回退",NULL,MB_OK);
            else
            {
               nArrayPos=nArrayPos-1; //按一次回退鍵就回退一字符位置
              CaretPos(hWnd,nArrayPos,cCharBuf,&xCaret,    &yCaret,nCharWidth);
              nNumChar=nNumChar-1;    //對現有字符總數進行計數
              InvalidateRect(hWnd,NULL,TRUE);//刷新用戶區并發送WM_PAINT消息  
            } 
            break; 
         } 

         if(wParam<=VK_ESCAPE) //處理按下Escape鍵消息
          {
           MessageBox(hWnd,"您現在不能按ESC鍵，請繼續其它操作",NULL,MB_OK);
              break;
          }

        if(nNumChar>=BufSize) //如寫入的字符數超過緩沖區大小，則報警
         {
            MessageBox(hWnd,"緩沖區已滿，不能再輸入字符了\n 若需要刪除字符，請用BackSpace鍵",NULL,MB_OK);
            break;
          }

        for(x=nNumChar;x>nArrayPos;x=x-1)
              cCharBuf[x]=cCharBuf[x-1];
            cCharBuf[nArrayPos]=(unsigned char)wParam;
            nArrayPos=nArrayPos+1;   
              nNumChar=nNumChar+1;
            CaretPos(hWnd,nArrayPos,cCharBuf,&xCaret,&yCaret,nCharWidth);
            InvalidateRect(hWnd,NULL,TRUE);
       }//end case WM_CHAR:      
break;

case WM_CREATE: //處理窗口創建消息
       {    
             hDC=GetDC(hWnd);
             GetTextMetrics(hDC,&tm); //獲取字體信息
            nLnHeight=tm.tmHeight+tm.tmExternalLeading;
             nCharWidth=tm.tmAveCharWidth;
            yCaret=nLnHeight;
            ReleaseDC(hWnd,hDC);
        }
            break;

case WM_SETFOCUS: //處理活動焦點消息
    {
           CreateCaret(hWnd,0,0,nLnHeight);
           CaretPos(hWnd,nArrayPos,cCharBuf,&xCaret,&yCaret,nCharWidth);
           ShowCaret(hWnd); //在活動焦點的窗口中顯示插字符
    }
break;

case WM_KILLFOCUS:         //處理失去焦點消息
                  DestroyCaret();
                  break;

case WM_KEYDOWN: //處理按下鍵消息
{
    switch(wParam)
    {
         case VK_END: //處理按下鍵為End時的消息
                   nArrayPos=nNumChar;//輸入位置從本行的末尾開始
                   CaretPos(hWnd,nArrayPos,cCharBuf,&xCaret,&yCaret,nCharWidth);
                   break;
         case VK_HOME:    //處理按下鍵為Home時的消息
                    nArrayPos=0;    //輸入位置為本行首位置
                  CaretPos(hWnd, nArrayPos,cCharBuf,    &xCaret,&yCaret,nCharWidth);
                  break;
         case VK_DELETE://處理按下鍵為Delete時的消息
                 if(nArrayPos==nNumChar)  //輸入位置處于本行的末尾
                    MessageBox(hWnd,"緩沖區已空，沒有字符可供刪除",NULL,MB_OK);
                 else
                 {
                      for(x=nArrayPos;x<nNumChar;x=x+1)
                        cCharBuf[x]=cCharBuf[x+1]; //每刪一字符，緩沖區中總字符數減1
                       nNumChar=nNumChar-1;
                       InvalidateRect(hWnd,NULL,TRUE); //用戶區刷新
                 }
                 break;

         case VK_LEFT: //處理按下左方向鍵時的消息
                  if(nArrayPos>0)
                  {
                      nArrayPos=nArrayPos-1;  //當前輸入位置往前移一個位置，再輸入字符時，等于插入字符
                      CaretPos(hWnd,nArrayPos,cCharBuf,&xCaret,&yCaret,nCharWidth);
                  }
                  else    //已經移到起始輸入位置，不能再往前了
                    MessageBox(hWnd,"您已經移動到起始位置，不能再往左移動了",NULL,MB_OK);
                   break; 

          case VK_RIGHT:        // 處理按下右方向鍵時的消息
                if(nArrayPos<nNumChar)  // 如果當前位置沒有到緩沖區的最后位置，還能向右移動
                 {
                  nArrayPos=nArrayPos+1;
                  CaretPos(hWnd,nArrayPos,cCharBuf,&xCaret,&yCaret,nCharWidth);
                }
                 else
                   
                   MessageBox(hWnd,"已經到緩沖區的末尾,不能再向右 移動了",NULL,MB_OK);
                  break;
     }
}//end case WM_KEYDOWN
 break;

case WM_PAINT: //處理重畫消息
{
   hDC=BeginPaint(hWnd,&PtStr);
   TextOut(hDC,nCharWidth,nLnHeight,cCharBuf,nNumChar);     //輸出緩沖區中的文本
   EndPaint(hWnd,&PtStr);
}
   break;

case WM_DESTROY: //處理結束應用程序消息
    PostQuitMessage(0);//結束應用程序
    break;

default://其他消息處理程序
   return(DefWindowProc(hWnd,iMessage,wParam,lParam)) ;
}//end 最外層switch

  return 0;
}

void WINAPI CaretPos(HWND hWnd,    int nArrayPos,char *cCharBuf,int *xCaret,int *yCaret,int nCharWidth)    //處理插字符位置的函數
{
    DWORD dWord; 
    HDC hDC;            //定義設備描述表句柄
    hDC=GetDC(hWnd);        //取得當前設備描述表句柄
    ReleaseDC(hWnd,hDC); 
    *xCaret=LOWORD(dWord)+nCharWidth;
    SetCaretPos(*xCaret,*yCaret);    //設置插字符位置坐標
}

BOOL InitWindowsClass(HINSTANCE hInstance)//初始化窗口類
{
  WNDCLASS WndClass;
  WndClass.cbClsExtra=0;
  WndClass.cbWndExtra=0;
  WndClass.hbrBackground=(HBRUSH)(GetStockObject(WHITE_BRUSH));
  WndClass.hCursor=LoadCursor(NULL,IDC_ARROW);
  WndClass.hIcon=LoadIcon(NULL,"END");
  WndClass.hInstance=hInstance;
  WndClass.lpfnWndProc=WndProc;
  WndClass.lpszClassName="WinFill";
  WndClass.lpszMenuName=NULL;
  WndClass.style=CS_HREDRAW|CS_VREDRAW;
  return RegisterClass(&WndClass);
}


BOOL InitWindows(HINSTANCE hInstance,int nCmdShow)//初始化窗口
{    
  HWND hWnd;
  hWnd=CreateWindow("WinFill",       //生成窗口
                 "填充示例程序",
                 WS_OVERLAPPEDWINDOW,
                 CW_USEDEFAULT,
                 0,
                 CW_USEDEFAULT,
                 0,
                 NULL,
                 NULL,
                 hInstance,
                 NULL);     
    if(!hWnd)    return FALSE;
    hWndMain=hWnd;
    ShowWindow(hWnd,nCmdShow);    //顯示窗口
    UpdateWindow(hWnd);        //繪制用戶區
    return TRUE;
}