Timer Demo

#include <windows.h>
#include <time.h>
#include <string.h>
#include <wchar.h>


#define MY_TIMER 1

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

WCHAR str[128] = L"Starting timer...";


int WINAPI wWinMain(HINSTANCE hInstance,
                    HINSTANCE hPrevInstance,
                    LPWSTR lpCmdLine,
                    int nCmdShow)
{
    MSG msg;
    WNDCLASSW wc;
    wc.style = CS_HREDRAW | CS_VREDRAW;
    wc.lpfnWndProc = WndProc;
    wc.cbClsExtra = 0;
    wc.cbWndExtra = 0;
    wc.hInstance = hInstance;
    wc.hIcon = LoadIcon(NULL, IDI_APPLICATION);
    wc.hCursor = LoadCursor(NULL, IDC_ARROW);
    wc.hbrBackground = (HBRUSH)(COLOR_WINDOW + 1);
    wc.lpszMenuName = NULL;
    wc.lpszClassName = L"TimerWindow";

    RegisterClassW(&wc);

    CreateWindowW(
        L"TimerWindow",
        L"Timer Demo",
        WS_OVERLAPPEDWINDOW | WS_VISIBLE,
        100,
        100,
        300,
        150,
        NULL,
        NULL,
        hInstance,
        NULL);

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

    return (int)msg.wParam;
}

LRESULT CALLBACK WndProc(HWND hwnd,
                         UINT msg,
                         WPARAM wParam,
                         LPARAM lParam)
{

    PAINTSTRUCT ps;
    HDC hdc;

    switch(msg)
    {

    case WM_CREATE:
        SetTimer(hwnd, MY_TIMER, 1000, NULL);
        break;

    case WM_TIMER:
        if(wParam == MY_TIMER)
        {
            time_t t;
            struct tm *newtime;
            time(&t);
            newtime = localtime(&t);
            wcsftime(
                str,
                128,
                L"%A %d %B %Y  %H:%M:%S",
                newtime);
            InvalidateRect(hwnd, NULL, TRUE);
        }
        break;

    case WM_PAINT:
        hdc = BeginPaint(hwnd, &ps);
        TextOutW(
            hdc,
            20,
            20,
            str,
            wcslen(str));
        EndPaint(hwnd, &ps);
        break;

    case WM_DESTROY:

        KillTimer(hwnd, MY_TIMER);
        PostQuitMessage(0);
        break;
        
    default:
        return DefWindowProc(hwnd, msg, wParam, lParam);
    }

    return 0;
}