Question

I am creating a DLL to check when the user presses the close button on the application window, it works fine, then I want to do it so that when _text global variable is empty, no message will be shown.
I can’t understand why a simple if (_text != “”) doesn’t work… am I doing something wrong?

#include <windows.h>
#define export extern "C" __declspec (dllexport)

WNDPROC GameWndProc = NULL;
HWND GameHwnd = NULL;
double _button_result = 0;
char* _text;
char* _title;

LRESULT CALLBACK SubClassWndProc(HWND hwnd, UINT uMsg, WPARAM wParam, LPARAM lParam)
{
    switch(uMsg) {
        case WM_CLOSE:

            if (_text != "") {
                if (MessageBox(GameHwnd, (LPSTR)_text, (LPSTR)_title, MB_YESNO|MB_APPLMODAL) == IDYES) {
                    _button_result = 1;
                    return 0;
                } else {
                    return 0;
                }
            }           

            _button_result = 1;
            return 0;
        break;
    }

    return CallWindowProc(GameWndProc, hwnd, uMsg, wParam, lParam);
}

export double _window_check_close_init(double window_handle, char* _msg_text, char* _msg_title)
{
    GameHwnd = (HWND)(int)window_handle;
    GameWndProc = (WNDPROC)SetWindowLongPtr(GameHwnd, GWL_WNDPROC, (LONG)SubClassWndProc);
    _text = _msg_text;
    _title = _msg_title;

    if (!GameWndProc) {
        return 0;
    }

    return 1;
}

export double _window_check_close()
{
    if (_button_result == 1) {
        _button_result = 0;
        return 1;
    } else {
        return 0;
    }
}

BOOL WINAPI DllMain(HINSTANCE hinstDLL, DWORD fdwReason, LPVOID lpvReserved)
{
    if (fdwReason == DLL_PROCESS_DETACH) {
        if (IsWindow(GameHwnd) && GameWndProc) {
            SetWindowLongPtr(GameHwnd, GWL_WNDPROC, (LONG)GameWndProc);
        }
    }
    return TRUE;
}

Answer 1

You’re checking if the pointer _text is equal to the empty string, not if the string pointed to by _text is equal to the empty string. You probably want to do something like:

if (strlen(_text) !=0)
... rest of your code...