Check for the presence of an Xembed tray on linux X11

checktray.c

#include <stdlib.h>
#include <stdio.h>
#include <X11/Xlib.h>

// Simple program to check for the presence of an Xembed tray
// Exits with status 0 if the tray exists

int main()
{
    Display *d = XOpenDisplay(NULL);
    if (!d) { fprintf(stderr, "XOpenDisplay failed\n"); return EXIT_FAILURE; }

    Atom a = XInternAtom(d, "_NET_SYSTEM_TRAY_S0", False);
    if (a == None) { fprintf(stderr, "XInternAtom failed\n"); return EXIT_FAILURE; }

    Window w = XGetSelectionOwner(d, a);
    if (w == None) { fprintf(stderr, "XGetSelectionOwner failed\n"); return EXIT_FAILURE; }

    return EXIT_SUCCESS;
}