win32 窗口 两种方式显示字符串

vs2013 新建一个win32 应用程序 ，项目名称:HelloTextOut，空项目。
添加一个源文件，名字为 HelloTextOut.cpp
内容为:

#include 
#include                                                  
#include                                                  
#include                                                   

LRESULT CALLBACK WndProc(HWND, UINT, WPARAM, LPARAM);

int WINAPI WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance,
    PSTR szCmdLine, int iCmdShow)
{
    static TCHAR szAppName[] = TEXT("HelloWin");
    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 Windows NT!"),
            szAppName, MB_ICONERROR);
        return 0;
    }

    hwnd = CreateWindow(szAppName,                  // window class name
        TEXT("The Hello Program"), // window caption
        WS_OVERLAPPEDWINDOW,        // window style
        CW_USEDEFAULT,              // initial x position
        CW_USEDEFAULT,              // initial y position
        CW_USEDEFAULT,              // initial x size
        CW_USEDEFAULT,              // initial y size
        NULL,                       // parent window handle
        NULL,                       // window menu handle
        hInstance,                  // program instance handle
        NULL);                     // creation parameters

    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)
{

    HDC         hdc;                                     // 1
    PAINTSTRUCT ps;                                      // 2

    TCHAR msg[] = _T("Hello, World!");                   // 3

    TCHAR szText[] = _T("Good Day!");                    // 4

    switch (message)
    {
    case WM_CLOSE:
        DestroyWindow(hwnd);
        break;

    case WM_DESTROY:
        PostQuitMessage(0);
        break;

    case WM_PAINT:                                       // 5

        hdc = BeginPaint(hwnd, &ps);                     // 6       

        TextOut(hdc, 50, 20, msg, _tcslen(msg));         // 7    

        EndPaint(hwnd, &ps);                             // 8

        break;        

    case WM_LBUTTONDOWN:                                 //9

        hdc = GetWindowDC(hwnd);                         //10

        TextOut(hdc, 50, 100, szText, _tcslen(szText));  //11

        ReleaseDC(hwnd, hdc);                            //12

        break;

    default:
        return DefWindowProc(hwnd, message, wParam, lParam);

    }

    return 0;
}

运行效果：如下