(WINAPI) Zamiana liter

#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;
HWND hTextWpisz, hButtonZmien, hTextCo, hTextNaCo, hTextWyswietl;
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);

    hTextWpisz = CreateWindowEx(0, "EDIT", NULL, WS_CHILD | WS_VISIBLE | WS_BORDER, 50, 50, 0, 0,
        hwnd, NULL, hInstance, NULL);
    hTextCo= CreateWindowEx(0, "EDIT", NULL, WS_CHILD | WS_VISIBLE | WS_BORDER, 50, 50, 0, 0,
        hwnd, NULL, hInstance, NULL);
    hTextNaCo = CreateWindowEx(0, "EDIT", NULL, WS_CHILD | WS_VISIBLE | WS_BORDER, 50, 50, 0, 0,
        hwnd, NULL, hInstance, NULL);
    hTextWyswietl = CreateWindowEx(0, "Static", NULL, WS_CHILD | WS_VISIBLE | WS_BORDER, 50, 50, 0, 0,
        hwnd, NULL, hInstance, NULL);
    hButtonZmien = CreateWindowEx(0, "BUTTON", "Zmien", 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)
{
    char text[250];
    char co[2];
    char naco[2];


    switch (msg)
    {
    case WM_COMMAND:
        if ((HWND)lParam == hButtonZmien)
        {
            GetWindowText(hTextWpisz, text, 250);
            GetWindowText(hTextCo, co, 2);
            GetWindowText(hTextNaCo, naco, 2);
            for (int i = 0; i < 250; i++)
            {
                if (text[i] == co[0])
                {
                    text[i] = naco[0];
                }
            }

            SetWindowText(hTextWyswietl, text);
        }
        break;
    case WM_CREATE:
        break;
    case WM_CLOSE:
        DestroyWindow(hwnd);
        break;
    case WM_DESTROY:
        PostQuitMessage(0);
        break;

    case WM_SIZE:
        GetClientRect(hwnd, &Rect);
        MoveWindow(hTextWpisz, Rect.right / 2 - 75, Rect.bottom / 2 - 100, 150, 50, TRUE);
        MoveWindow(hTextCo, Rect.right / 2 - 25, Rect.bottom / 2 - 40, 25, 25, TRUE);
        MoveWindow(hTextNaCo, Rect.right / 2, Rect.bottom / 2 - 40, 25, 25, TRUE);
        MoveWindow(hButtonZmien, Rect.right / 2 - 25, Rect.bottom / 2 , 50, 25, TRUE);
        MoveWindow(hTextWyswietl, Rect.right / 2 -75, Rect.bottom / 2 + 30 , 150, 50, TRUE);

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

    return 0;
}