onlyquitonempty: refactoring patch to only take client windows into

consideration when deciding whether or not to allow dwm to quit

As per the original patch
https://dwm.suckless.org/patches/onlyquitonempty/

it used XQueryTree to get a count of the number of windows open to
determine whether to allow the window manager to exit.

This meant that the empty quit count variable would have to take
into account background windows such as the bar, which has side
effects like plugging in another monitor could mean that you would
not longer be allowed to quit dwm until the monitor is removed.

Likewise a systray and each systray icon would give a +1 to the
number of windows in the system.

This is unintuitive to understand and convoluted to explain, hence
the refactoring here to use the more sane approach of only counting
the number of client windows that the window manager manages.

This is an old idea which was intentionally not added to
dwm-flexipatch due to the aim of staying true to the original patch
(as in if you were to patch that manually you would get the same
experience as you had when trying the patch out in dwm-flexipatch).

This is ref. discussion in #194.

config.def.h

@@ -100,7 +100,7 @@ static int fakefsindicatortype           = INDICATOR_PLUS;
 static int floatfakefsindicatortype      = INDICATOR_PLUS_AND_LARGER_SQUARE;
 #endif // FAKEFULLSCREEN_CLIENT_PATCH
 #if ONLYQUITONEMPTY_PATCH
-static const int quit_empty_window_count = 2;   /* only allow dwm to quit if no windows are open, value here represents number of deamons */
+static const int quit_empty_window_count = 0;   /* only allow dwm to quit if no (<= count) windows are open */
 #endif // ONLYQUITONEMPTY_PATCH
 #if BAR_EXTRASTATUS_PATCH
 static const char statussep              = ';'; /* separator between status bars */

dwm.c

@@ -2744,27 +2744,23 @@ quit(const Arg *arg)
 	#if COOL_AUTOSTART_PATCH
 	size_t i;
 	#endif // COOL_AUTOSTART_PATCH
+	#if RESTARTSIG_PATCH
+	restart = arg->i;
+	#endif // RESTARTSIG_PATCH
 	#if ONLYQUITONEMPTY_PATCH
-	unsigned int n;
-	Window *junk = malloc(1);
+	Monitor *m;
+	Client *c;
+	unsigned int n = 0;
 
-	XQueryTree(dpy, root, junk, junk, &junk, &n);
+	for (m = mons; m; m = m->next)
+		for (c = m->clients; c; c = c->next, n++);
 
-	if (n <= quit_empty_window_count)
-	{
-		#if RESTARTSIG_PATCH
-		restart = arg->i;
-		#endif // RESTARTSIG_PATCH
+	if (restart || n <= quit_empty_window_count)
 		running = 0;
-	}
 	else
-		printf("[dwm] not exiting (n=%d)\n", n);
+		fprintf(stderr, "[dwm] not exiting (n=%d)\n", n);
 
-	free(junk);
 	#else // !ONLYQUITONEMPTY_PATCH
-	#if RESTARTSIG_PATCH
-	restart = arg->i;
-	#endif // RESTARTSIG_PATCH
 	running = 0;
 	#endif // ONLYQUITONEMPTY_PATCH