/* xclass: WM_CLASS set-then-delete probe.
 *
 * Maps a titled X11 window with NO class, then sets WM_CLASS, then deletes
 * it: the delete emits set_class with class==NULL while the title is set.
 * The compositor must mirror "" (not raw NULL) onto the taskbar handles --
 * passing NULL into the foreign-toplevel set_app_id/update_state calls
 * segfaults inside wlroots' strdup (regression test for that crash).
 *
 * usage: xclass <hold-seconds>  (total runtime ~= 4 + max(hold-4, 0))
 */
#define _POSIX_C_SOURCE 200809L
#include <X11/Xlib.h>
#include <X11/Xatom.h>
#include <X11/Xutil.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>

int main(int argc, char **argv) {
    int hold = argc > 1 ? atoi(argv[1]) : 6;
    Display *d = XOpenDisplay(NULL);
    if (!d) {
        fprintf(stderr, "xclass: cannot open display\n");
        return 1;
    }
    int scr = DefaultScreen(d);
    Window w = XCreateSimpleWindow(d, RootWindow(d, scr), 0, 0, 400, 300, 0,
                                   BlackPixel(d, scr), 0x804020UL);
    XStoreName(d, w, "xclass-frame");
    pid_t pid = getpid();
    Atom apid = XInternAtom(d, "_NET_WM_PID", False);
    XChangeProperty(d, w, apid, XA_CARDINAL, 32, PropModeReplace,
                    (unsigned char *)&pid, 1);
    /* NOTE: no WM_CLASS yet (class == NULL server-side). */
    XMapWindow(d, w);
    XFlush(d);
    fprintf(stderr, "[xclass] mapped, no class\n");
    sleep(2);
    XClassHint *ch = XAllocClassHint();
    ch->res_name = "xclass-probe";
    ch->res_class = "XClassProbe";
    XSetClassHint(d, w, ch);
    XFree(ch);
    XFlush(d);
    fprintf(stderr, "[xclass] class set\n");
    sleep(2);
    Atom wmclass = XInternAtom(d, "WM_CLASS", False);
    XDeleteProperty(d, w, wmclass);
    XFlush(d);
    fprintf(stderr, "[xclass] class deleted (NULL)\n");
    sleep(hold > 4 ? (unsigned)(hold - 4) : 0);
    return 0;
}