windows 简单窗口

LRESULT CALLBACK HelloWndProc(HWND hwnd, UINT uMsg, WPARAM wParam, LPARAM lParam)      {      HDC         hdc;    PAINTSTRUCT ps;     static int cxClient;       // 客户端的宽度和高度，在窗口发生变化的时候，windows都会发送WM_SIZE消息，该消息的lParam高位保存高度，地位保存宽度   static int cyClient;  switch(uMsg)      {      case WM_CREATE:  {  hdc = GetDC(hwnd);                // 在非WM_PAINT消息里面调用此方法获得HDC   ReleaseDC(hwnd, hdc);  }  break;  case WM_SIZE:  {  // 在窗口每次发生变化的时候，获取客户端高度和宽度   cxClient = LOWORD(lParam);  cyClient = HIWORD(lParam);  }  break;  case WM_PAINT:    {    hdc = BeginPaint(hwnd, &ps);  // WM_PAINT 消息里面使用该方法获得HDC   EndPaint(hwnd,&ps);    }    break;    case WM_DESTROY:      {      PostQuitMessage(0);  // 发送 WM_CLOSE, 形参 0 将会传递给 WPARAM     }      break;  case WM_CLOSE:      {          DestroyWindow(hwnd); // 销毁窗口       }      break;      default:      return DefWindowProc(hwnd,uMsg,wParam,lParam);      }      return 0;      }   int APIENTRY _tWinMain(HINSTANCE hInstance,  HINSTANCE hPrevInstance,  LPTSTR    lpCmdLine,  int       nCmdShow)  {  // 设计一个窗口类       WNDCLASS wndclass;      wndclass.style         = CS_VREDRAW | CS_HREDRAW;      wndclass.lpfnWndProc = HelloWndProc;   // 由windows系统调用     wndclass.cbClsExtra    = 0;      wndclass.cbWndExtra    = 0;      wndclass.hInstance     = hInstance;      wndclass.hIcon         = LoadIcon(NULL, MAKEINTRESOURCE(IDI_WINLOGO));      wndclass.hCursor       = LoadCursor(NULL, MAKEINTRESOURCE(IDC_ARROW));      wndclass.hbrBackground = (HBRUSH)GetStockObject(WHITE_BRUSH);      wndclass.lpszMenuName  = NULL;      wndclass.lpszClassName = _T("hellownd");  // 此处是指定窗口类名称，用于关联窗口，CreateWindow第一个参数     // 注册窗口类       RegisterClass(&wndclass);      // 创建窗口       HWND hwnd = CreateWindow(_T("hellownd"), _T("hellownd"), WS_OVERLAPPEDWINDOW,     CW_USEDEFAULT, 0, CW_USEDEFAULT, 0, NULL, NULL, hInstance, NULL);    // WM_CREATE   // 显示窗口       ShowWindow(hwnd, SW_SHOW);    // WM_SIZE   // 更新窗口       UpdateWindow(hwnd);    // WM_PAINT   // 消息循环       MSG msg;      while(GetMessage(&msg, NULL, 0, 0))      {      TranslateMessage(&msg);      DispatchMessage(&msg);      }      UnregisterClass(_T("hellownd"), hInstance);      return msg.wParam; // 来自与PostQuitMessage中的参数    }