(WINAPI) Stoper

#include <Windows.h>
#include <math.h>
#include <list>
#include <stdio.h>

using namespace std;

LPCSTR NazwaKlasy = TEXT("Klasa Okienka");
MSG Komunikat;
HDC hdc;
HWND hwnd;
RECT Rect;
PAINTSTRUCT ps;
HWND hText,hButtonStart,hButtonStop,hButtonReset;
int m, s, ms;
bool start = NULL;
char buf[50];
SYSTEMTIME czasAktualny, czasStartu;
LRESULT CALLBACK WndProc(HWND hwnd, UINT msg, WPARAM wParam, LPARAM lParam);

int WINAPI WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance, LPSTR lpCmdLine, int nCmdShow)
{
    WNDCLASSEX wc;
    wc.cbSize = sizeof(WNDCLASSEX);
    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 = NazwaKlasy;
    wc.hIconSm = LoadIcon(NULL, IDI_APPLICATION);

    if (!RegisterClassEx(&wc))
    {
        MessageBox(NULL, TEXT("Nie mozna utworzyc okna"), TEXT("Niestety..."),
            MB_ICONEXCLAMATION | MB_OK);
        return 1;
    }

    hwnd = CreateWindowEx(WS_EX_CLIENTEDGE, NazwaKlasy, TEXT("Oto okienko"), WS_OVERLAPPEDWINDOW,
        CW_USEDEFAULT, CW_USEDEFAULT, 800, 400, NULL, NULL, hInstance, NULL);

     hText = CreateWindowEx(0, "STATIC", NULL, WS_CHILD | WS_VISIBLE | WS_BORDER, 50, 50, 0, 0,
        hwnd, NULL, hInstance, NULL);

     hButtonStart = CreateWindowEx(0, "BUTTON", "Start", WS_CHILD | WS_VISIBLE,
         0, 0, 150, 30, hwnd, NULL, hInstance, NULL);

    hButtonStop = CreateWindowEx(0, "BUTTON", "Stop", WS_CHILD | WS_VISIBLE,
         0, 0, 150, 30, hwnd, NULL, hInstance, NULL);

    hButtonReset = CreateWindowEx(0, "BUTTON", "Reset", WS_CHILD | WS_VISIBLE,
         0, 0, 150, 30, hwnd, NULL, hInstance, NULL);

    if (hwnd == NULL)
    {
        MessageBox(NULL, TEXT("Okno odmówiło przyjścia na świat!"), TEXT("Ale kicha..."), MB_ICONEXCLAMATION);
        return 1;
    }

    ShowWindow(hwnd, nCmdShow);
    UpdateWindow(hwnd);

    while (GetMessage(&Komunikat, NULL, 0, 0))
    {
        TranslateMessage(&Komunikat);
        DispatchMessage(&Komunikat);
    }
    return Komunikat.wParam;
}
LRESULT CALLBACK WndProc(HWND hwnd, UINT msg, WPARAM wParam, LPARAM lParam)
{


    switch (msg)
    {
    case WM_COMMAND:
        if ((HWND)lParam == hButtonStart) { start = TRUE; GetLocalTime(&czasStartu); }
        if ((HWND)lParam == hButtonStop) start = NULL;
        if ((HWND)lParam == hButtonReset)
        {
            ms = 0, m = 0, s = 0;
            wsprintf(buf, "%02d:%02d:%02d", m, s, ms);
            SetWindowText(hText, buf);
        }
        break;
    case WM_CREATE:

        SetTimer(hwnd, 1, 10, 0);
        break;
    case WM_TIMER:
        if (start == TRUE)
        {
            GetLocalTime(&czasAktualny);
            int r;
            r = (czasAktualny.wMinute - czasStartu.wMinute) * 60000 + (czasAktualny.wSecond - czasStartu.wSecond) * 1000 + (czasAktualny.wMilliseconds - czasStartu.wMilliseconds);
            m = (r / 60000);
            s = (r % 60000) / 1000;
            ms = ((r % 60000) % 1000) / 100;
            wsprintf(buf, "%02d:%02d:%02d", m,s,ms);
            SetWindowText(hText, buf);
            InvalidateRect(hwnd, 0, 1);
        }
        break;
    case WM_CLOSE:
        DestroyWindow(hwnd);
        break;
    case WM_DESTROY:
        KillTimer(hwnd, 1);
        PostQuitMessage(0);
        break;

    case WM_SIZE:

        GetClientRect(hwnd, &Rect);
        MoveWindow(hText, Rect.right / 2 - 75, Rect.bottom / 2 - 50, 150, 50, TRUE);
        MoveWindow(hButtonStart, Rect.right / 2 - 75, Rect.bottom / 2, 50, 25, TRUE);
        MoveWindow(hButtonStop, Rect.right / 2 - 25, Rect.bottom / 2 , 50, 25, TRUE);
        MoveWindow(hButtonReset, Rect.right / 2 + 25, Rect.bottom / 2 , 50, 25, TRUE);

        break;
    default:
        return DefWindowProc(hwnd, msg, wParam, lParam);
    }

    return 0;
}