win32 窗口 两种方式显示字符串

#include <windows.h>
#include <stdlib.h>
#include <string.h>
#include <tchar.h>

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;
}