Question

How to convert the HWND to LPCSTR and display it in a MessageBox with C++ Win32 API

Answer 1

#define WIN32_LEAN_AND_MEAN
#define NOMINMAX

#include <windows.h>
#include <sstream>

LRESULT CALLBACK WndProc(HWND hwnd, UINT msg, WPARAM wparam, LPARAM lparam);

int CALLBACK WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance, LPSTR lpCmdLine, int nCmdShow)
{
    // Create a window
    HWND hwnd;
    {
        WNDCLASSEXW winClass = {};
        winClass.cbSize = sizeof(WNDCLASSEXW);
        winClass.style = CS_HREDRAW | CS_VREDRAW;
        winClass.lpfnWndProc = &WndProc;
        winClass.hInstance = hInstance;
        winClass.hCursor = LoadCursorW(0, IDC_ARROW);
        winClass.lpszClassName = L"WindowClassName";

        if (!RegisterClassEx(&winClass)) {
            MessageBoxA(0, "RegisterClassEx failed", "Fatal Error", MB_OK);
            return GetLastError();
        }

        RECT rect = { 0, 0, 1024, 768 };
        AdjustWindowRectEx(&rect, WS_OVERLAPPEDWINDOW, FALSE, WS_EX_OVERLAPPEDWINDOW);
        LONG width = rect.right - rect.left;
        LONG height = rect.bottom - rect.top;

        hwnd = CreateWindowEx(WS_EX_OVERLAPPEDWINDOW,
            winClass.lpszClassName,
            L"A Windows",
            WS_OVERLAPPEDWINDOW | WS_VISIBLE,
            CW_USEDEFAULT, CW_USEDEFAULT,
            width,
            height,
            0, 0, hInstance, 0);

        if (!hwnd) {
            MessageBoxA(0, "CreateWindowEx failed", "Fatal Error", MB_OK);
            return GetLastError();
        }
    }

    // Convert the HWND to LPCSTR and display it in a MessageBox 

    std::ostringstream ss;
    ss << std::hex << hwnd;
    std::string wstr = ss.str();
    LPCSTR lpcstr_hwnd = wstr.c_str();
    MessageBoxA(0, lpcstr_hwnd, "Info", MB_OK);

    bool running = true;
    while (running) {
        MSG msg = {};
        while (PeekMessageW(&msg, 0, 0, 0, PM_REMOVE)) {
            if (msg.message == WM_QUIT) {
                running = false;
            }
            TranslateMessage(&msg);
            DispatchMessageW(&msg);
        }
    }

    return 0;
}

LRESULT CALLBACK WndProc(HWND hwnd, UINT msg, WPARAM wparam, LPARAM lparam)
{
    LRESULT result = 0;
    switch (msg)
    {
    case WM_KEYDOWN:
    {
        if (wparam == VK_ESCAPE) {
            DestroyWindow(hwnd);
        }
        break;
    }
    case WM_DESTROY:
    {
        PostQuitMessage(0);
        break;
    }
    default:
        result = DefWindowProcW(hwnd, msg, wparam, lparam);
    }

    return result;
}



/*
run:

00000000003F1A40

*/

 

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