apply autostart patch from dwm

https://dwm.suckless.org/patches/cool_autostart/

config.def.h

@@ -10,6 +10,12 @@ static const float fullscreen_bg[]         = {0.1, 0.1, 0.1, 1.0};
 /* tagging - tagcount must be no greater than 31 */
 static const int tagcount = 9;
 
+/* Autostart */
+static const char *const autostart[] = {
+        "wbg", "/path/to/your/image", NULL,
+        NULL /* terminate */
+};
+
 static const Rule rules[] = {
 	/* app_id     title       tags mask     isfloating   monitor */
 	/* examples:

dwl.c

@@ -231,6 +231,7 @@ static void arrange(Monitor *m);
 static void arrangelayer(Monitor *m, struct wl_list *list,
 		struct wlr_box *usable_area, int exclusive);
 static void arrangelayers(Monitor *m);
+static void autostartexec(void);
 static void axisnotify(struct wl_listener *listener, void *data);
 static void buttonpress(struct wl_listener *listener, void *data);
 static void chvt(const Arg *arg);
@@ -417,6 +418,9 @@ static Atom netatom[NetLast];
 /* attempt to encapsulate suck into one file */
 #include "client.h"
 
+static pid_t *autostart_pids;
+static size_t autostart_len;
+
 /* function implementations */
 void
 applybounds(Client *c, struct wlr_box *bbox)
@@ -557,6 +561,27 @@ arrangelayers(Monitor *m)
 	}
 }
 
+void
+autostartexec(void) {
+	const char *const *p;
+	size_t i = 0;
+
+	/* count entries */
+	for (p = autostart; *p; autostart_len++, p++)
+		while (*++p);
+
+	autostart_pids = calloc(autostart_len, sizeof(pid_t));
+	for (p = autostart; *p; i++, p++) {
+		if ((autostart_pids[i] = fork()) == 0) {
+			setsid();
+			execvp(*p, (char *const *)p);
+			die("dwl: execvp %s:", *p);
+		}
+		/* skip arguments */
+		while (*++p);
+	}
+}
+
 void
 axisnotify(struct wl_listener *listener, void *data)
 {
@@ -657,10 +682,20 @@ checkidleinhibitor(struct wlr_surface *exclude)
 void
 cleanup(void)
 {
+	size_t i;
+
 #ifdef XWAYLAND
 	wlr_xwayland_destroy(xwayland);
 #endif
 	wl_display_destroy_clients(dpy);
+
+	/* kill child processes */
+	for (i = 0; i < autostart_len; i++) {
+		if (0 < autostart_pids[i]) {
+			kill(autostart_pids[i], SIGTERM);
+			waitpid(autostart_pids[i], NULL, 0);
+		}
+	}
 	if (child_pid > 0) {
 		kill(child_pid, SIGTERM);
 		waitpid(child_pid, NULL, 0);
@@ -1962,6 +1997,7 @@ run(char *startup_cmd)
 		die("startup: backend_start");
 
 	/* Now that the socket exists and the backend is started, run the startup command */
+	autostartexec();
 	if (startup_cmd) {
 		int piperw[2];
 		if (pipe(piperw) < 0)
@@ -2134,15 +2170,7 @@ void
 setup(void)
 {
 	struct sigaction sa_term = {.sa_flags = SA_RESTART, .sa_handler = quitsignal};
-	struct sigaction sa_sigchld = {
+	struct sigaction sa_sigchld = { .sa_flags = SA_RESTART, .sa_handler = sigchld};
-#ifdef XWAYLAND
-		.sa_flags = SA_RESTART,
-		.sa_handler = sigchld,
-#else
-		.sa_flags = SA_NOCLDSTOP | SA_NOCLDWAIT | SA_RESTART,
-		.sa_handler = SIG_IGN,
-#endif
-	};
 	sigemptyset(&sa_term.sa_mask);
 	sigemptyset(&sa_sigchld.sa_mask);
 	/* The Wayland display is managed by libwayland. It handles accepting
@@ -2357,8 +2385,22 @@ sigchld(int unused)
 #ifdef XWAYLAND
 			&& (!xwayland || in.si_pid != xwayland->server->pid)
 #endif
-			)
+			) {
+		pid_t *p, *lim;
 		waitpid(in.si_pid, NULL, 0);
+		if (in.si_pid == child_pid)
+			child_pid = -1;
+		if (!(p = autostart_pids))
+			continue;
+		lim = &p[autostart_len];
+
+		for (; p < lim; p++) {
+			if (*p == in.si_pid) {
+				*p = -1;
+				break;
+			}
+		}
+	}
 }
 
 void