最初级的记事本

来自于windows程序设计， 最初级的记事本， 且看代码：

#include <windows.h>
#define BUFFER(x, y) *(pBuffer + y * cxBuffer + x)

LRESULT CALLBACK WndProc(HWND, UINT, WPARAM, LPARAM);
int WINAPI WinMain(HINSTANCE hInstance,
         HINSTANCE hPrevInstance,
         PSTR szCmdLine,
         int iCmdShow) {
  static TCHAR szAppName[] = TEXT("TYPER");
  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(WHITE_BRUSH);
  wndclass.lpszMenuName = NULL;
  wndclass.lpszClassName = szAppName;

  if(!RegisterClass(&wndclass)) {
    MessageBox(NULL,
     TEXT("This program requires WINDOW NT!"),
     szAppName,
     MB_ICONERROR);
    return 0;
  }

  hwnd = CreateWindow(szAppName,
         TEXT("Typing Program"),
         WS_OVERLAPPEDWINDOW,
         CW_USEDEFAULT,
         CW_USEDEFAULT,
         CW_USEDEFAULT,
         CW_USEDEFAULT,
         NULL,
         NULL,
         hInstance,
         NULL);

  ShowWindow(hwnd, iCmdShow);
  UpdateWindow(hwnd);

  while(GetMessage(&msg, NULL, 0, 0)) {
    TranslateMessage(&msg);
    DispatchMessage(&msg);
  }

  return msg.wParam;
}

LRESULT CALLBACK WndProc(HWND hwnd,
             UINT message,
             WPARAM wParam,
             LPARAM lParam) {
  static DOWRD dwCharSet = DEFAULT_CHARSET;
  static int cxChar, cyChar, cxClient, cyClient,
    cxBuffer, cyBuffer, xCaret, yCaret;
  static TCHAR* pBuffer = NULL;
  HDC hdc;
  int x, y, i;
  PAINTSTRUCT ps;
  TEXTMETRIC tm;

  switch(message) {
    case WM_INPUTLANGCHANGE:
    dwCharSet = wParam;

  case WM_CREATE:
    hdc = GetDC(hwnd);
    SelectObject(hdc, CreateFont(0, 0, 0, 0,
                 0, 0, 0, 0,
                 dwCharset, 0, 0, 0,
                 FIXED_PITCH, NULL));
    GetTextMetrics(hdc, &tm);
    cxChar = tm.tmAveCharWidth;
    cyChar =tm.tmHeight;
    DeleteObject(SelectObject(hdc, GetStockObject(SYSTEM_FONT)));
    ReleaseDC(hwnd, hdc);

  case WM_SIZE:
    if(message == WM_SIZE) {
      cxClient = LOWORD(lParam);
      cyClient = HIWORD(lParam);
    }

    // calculate window size in characters

    cxBuffer = max(1, cxClient / cxChar);
    cyBuffer = max(1, cyClient / cyChar);

    // allocate memory for buffer and clear it

    if(pBuffer != NULL)
      free(pBuffer);
    pBuffer = (TCHAR*)malloc(cxBuffer * cyBuffer * sizeof(TCHAR));

    for(y = 0; y < cyBuffer, y++)
      for(x = 0; x < cxBuffer, x++)
    BUFFER(x, y) = '';

    xCaret = 0;
    yCaret = 0;

    if(hwnd = GetFocus())
      SetCaretPos(xCaret * cxChar, yCaret * cyChar);
    InvalidateRect(hwnd, NULL, TRUE);
    return 0;

  case WM_SETFOCUS:
    CreateCaret(hwnd, NULL, cxChar, cyChar);
    SetCaretPos(xCaret * cxChar, yCaret * cyChar);
    ShowCaret(hwnd);
    return 0;

  case WM_KILLFOCUS:
    HideCaret(hwnd);
    DestroyCaret();
    return 0;

  case WM_KEYDOWN:
    switch(wParam) {
    case VK_HOME:
      xCaret = 0;
      break;
    case VK_END:
      xCaret = cxBuffer - 1;
      break;
    case VK_PRIOR:
      yCaret = 0;
      break;
    case VK_NEXT:
      yCaret = cyBuffer - 1;
      break;
    case VK_LEFT:
      xCaret = max(xCaret - 1, 0);
      break;
    case VK_RIGHT:
      xCaret = min(xCaret + 1, cxBuffer - 1);
      break;
    case VK_UP:
      yCaret = max(yCaret - 1, 0);
      break;
    case VK_DOWN:
      yCaret = min(yCaret + 1, cyBuffer - 1);
      break;
    case VK_DELETE:
      for(x = xCaret; x < cxBuffer - 1; x++)
    BUFFER(x, yCaret) = BUFFER(x + 1, yCaret);

      BUFFER(cxBuffer - 1, yCaret) = '';
      HideCaret(hwnd);
      hdc = GetDC(hwnd);

      SelectObject(hdc, CreateFont(0, 0, 0, 0,
                 0, 0, 0, 0,
                 dwCharSet, 0, 0, 0,
                 FIXED_PITCH, NULL));
      TextOut(hdc, xCaret * cxChar, yCaret * cyChar,
     &BUFFER(xCaret, yCaret), cxBuffer - xCaret);
      DeleteObject(SelectObject(hdc,
                GetStockObject(SYSTEM_FONT)));
      ReleaseDC(hwnd, hdc);
      ShowCaret(hwnd);
      break;
    }

    SetCaretPos(xCaret * cxChar, yCaret * cyChar);
    return 0;

  case WM_CHAR:
    for(i = 0; i < (int)LOWORD(lParam); i++) {
      switch(wParam) {
      case '\b':
    if(xCaret > 0) {
     xCaret--;
     SendMessage(hwnd, WM_KEYDOWN, VK_DELETE, 1);
    }
    break;
      case '\t':
    do {
     SendMessage(hwnd, WM_CHAR, '', 1)
     }while(xCaret % 8 != 0);
    break;
      case '\n':
    if(++yCaret == cyBuffer)
     yCaret = 0;
    break;
      case '\r':
    xCaret = 0;
    if(++yCaret == cyBuffer)
     yCaret = 0;
    break;
      case '\x1B':
    for(y = 0;y < cyBuffer; y++)
     for(x = 0; x < cxBuffer; x++)
     BUFFER(x, y) = '';
    xCaret = 0;
    yCaret = 0;

    InvalidateRect(hwnd, NULL, FALSE);
    break;

      default:
    BUFFER(xCaret, yCaret) = (TCHAR)wParam;
    HideCaret(hwnd);
    hdc = GetDC(hwnd);
    SelectObject(hdc, CreateFont(0, 0, 0, 0,
                 0, 0, 0, 0,
                 FIXED_PITCH, NULL));
    TextOut(hdc, xCaret * cxChar,
        yCaret * cyChar, &BUFFER(xCaret, yCaret), 1);
    DeleteObject(
         SelectObject(hdc, GetStockObject(SYSTEM_FONT)));
    ReleaseDC(hwnd, hdc);
    ShowCaret(hwnd);

    if(++xCaret == cxBuffer) {
     xCaret = 0;
     if(++yCaret == cyBuffer)
     yCaret = 0;
    }
    break;
      }
    }

    SetCaretPos(xCaret * cxChar, yCaret * cyChar);
    return 0;

  case WM_PAINT:
    hdc = BeginPaint(hwnd, &ps);
    SelectObject(hdc, CreateFont(0, 0, 0, 0,
                 0, 0, 0, 0,
                 dwCharset, 0, 0, 0,
                 FIXED_PITCH, NULL));
    for(y = 0; y < cyBuffer; y++)
      TextOut(hdc, 0, y * cyChar, &BUFFER(0, y), cxBuffer);
    DeleteObject(SelectObject(hdc,
             GetStockObject(SYSTEM_FONT)));
    EndPaint(hwnd, &ps);
    return 0;

  case WM_DESTROY:
    PostQuitMessage(0);
    return 0;
  }

  return DefWindowProc(hwnd, message, wParam, lParam);
}