// X11 Fullscreen window example

#include <X11/Xlib.h>

int main()
{
    Display* d = XOpenDisplay(NULL);

    Window w = XCreateSimpleWindow(d, DefaultRootWindow(d), 0, 0, 200, 100, 0,
                                   BlackPixel(d, DefaultScreen(d)),
                                   WhitePixel(d, DefaultScreen(d)));
    XSelectInput(d, w, StructureNotifyMask);
    XMapWindow(d, w);

    XClientMessageEvent msg = {
        .type = ClientMessage,
        .display = d,
        .window = w,
        .message_type = XInternAtom(d, "_NET_WM_STATE", True),
        .format = 32,
        .data = { .l = {
            1 /* _NET_WM_STATE_ADD */,
            XInternAtom(d, "_NET_WM_STATE_FULLSCREEN", True),
            None,
            0,
            1
        }}
    };

    XSendEvent(d, DefaultRootWindow(d), False, SubstructureRedirectMask | SubstructureNotifyMask, (XEvent*)&msg);

    for (;;)
    {
        XEvent e;
        XNextEvent(d, &e);
    }

    XCloseDisplay(d);
}