Disable X-Button Icon on the top of the right in Messagebox Using C++ Win32 API?

Question

i am using C++ win32 API...

i have a Windows messagebox contain OKCANCEL Button...

the messagebox have a close(X-Button) on the right top...

Answer 1

There's most likely a bigger problem beyond what you've given us, but one way to disable the close button is to set the class style to include CS_NOCLOSE, which you can do with a window handle and SetClassLongPtr. Consider the following full example:

#include 

DWORD WINAPI CreateMessageBox(void *) { //threaded so we can still work with it
    MessageBox(nullptr, "Message", "Title", MB_OKCANCEL);
    return 0;
}

int main() {
    HANDLE thread = CreateThread(nullptr, 0, CreateMessageBox, nullptr, 0, nullptr);

    HWND msg;
    while (!(msg = FindWindow(nullptr, "Title"))); //The Ex version works well for you

    LONG_PTR style = GetWindowLongPtr(msg, GWL_STYLE); //get current style
    SetWindowLongPtr(msg, GWL_STYLE, style & ~WS_SYSMENU); //remove system menu 

    WaitForSingleObject(thread, INFINITE); //view the effects until you close it
}