Xlib + Unity Only close allowed action - c

Question

I just want to make a sample app when the only possible action is close.
Is this possible with Unity(Ubuntu) ?
Do i make a mistake ?
#include <stdio.h>
#include <X11/Xlib.h>
#include <X11/Xos.h>
#include <X11/Xatom.h>
static void only_close(Display *display, Window window)
{
int retval;
Atom aa = XInternAtom(display, "_NET_WM_ALLOWED_ACTIONS", False);
Atom close = XInternAtom(display, " _NET_WM_ACTION_CLOSE", False);
retval = XChangeProperty(display, window, aa, XA_ATOM, 32, PropModeReplace, (unsigned char*)close, 1);
printf("###### XChangeProperty() reted %d\n", retval);
}
int main()
{
Display *dis;
Window win;
dis = XOpenDisplay(NULL);
win = XCreateSimpleWindow(dis, RootWindow(dis, 0), 1, 1, 500, 500, \
0, BlackPixel (dis, 0), BlackPixel(dis, 0));
XMapWindow(dis, win);
printf("window %i\n", (int)win);
only_close(dis, win);
XFlush(dis);
sleep(10);
return(0);
}

Answer 1

First, you need (unsigned char*)&close (an address of the data)
Second, you are setting the property too early, before WM has a chance to manage the window. A WM must discard the old value of this property when it first manages the window. Try after the first expose event, or just after a delay of 1 second.
Third, it is not guaranteed to work. On my machine (not Unity) the window actions in the taskbar are indeed disabled, but the window frame still has them the WM still allows them. I don't know if it's a bug in my WM or not.