Preserve asleep disabled outputs in output config

mapnotify() stores the client's scene tree in client_surface(c)->data;
checkidleinhibitor() later reads it back as a wlr_scene_tree and calls
wlr_scene_node_coords() on it. unmapnotify() frees the scene tree with
wlr_scene_node_destroy() but leaves surface->data dangling, so the next
arrange() -> checkidleinhibitor() dereferences freed memory and crashes
(SIGSEGV) whenever an idle inhibitor outlives the unmap.

Reset the pointer to NULL on unmap so the existing !tree guard handles it.

README.md

@@ -1,7 +1,7 @@
 # dwl - dwm for Wayland
 
-Join us on our [Discord server]
-Or Matrix: [#dwl-official:matrix.org]
+Join us on our [Discord server]  
+Or Matrix: [#dwl-official:matrix.org]  
 Or on our IRC channel: [#dwl on Libera Chat]
 
 dwl is a compact, hackable compositor for [Wayland] based on [wlroots]. It is
@@ -24,12 +24,14 @@ with each release on the [release] page
 
 ### Development branch [main]
 Active development progresses on the `main` branch. The `main` branch is built
-against a late (and often changing) git commit of wlroots. While the adventurous
-are welcome to use `main`, it is a rocky road. Using `main` requires that the
-user be willing to chase git commits of wlroots. Testing development pull
-requests may involve merging unmerged pull requests in [wlroots]' git repository
-and/or git commits of wayland.
-  
+against the latest release of [wlroots]. PRs should target this branch unless they
+depend on functionality that is not in the current release of `wlroots`.
+
+### Preview branch [wlroots-next]
+The `wlroots-next` branch is built against the git version of [wlroots], which
+is unstable and changes frequently. PRs requiring functionality from the git
+version of `wlroots` should target this branch.
+
 ### Building dwl
 dwl has the following dependencies:
 - libinput
@@ -203,6 +205,7 @@ inspiration, and to the various contributors to the project, including:
 [dwl-patches]: https://codeberg.org/dwl/dwl-patches
 [list of useful resources on our wiki]: https://codeberg.org/dwl/dwl/wiki/Home#migrating-from-x
 [main]: https://codeberg.org/dwl/dwl/src/branch/main
+[wlroots-next]: https://codeberg.org/dwl/dwl/src/branch/wlroots-next
 [release]: https://codeberg.org/dwl/dwl/releases
 [runit]: http://smarden.org/runit/faq.html#userservices
 [s6]: https://skarnet.org/software/s6/
@@ -210,4 +213,4 @@ inspiration, and to the various contributors to the project, including:
 [wiki]: https://codeberg.org/dwl/dwl/wiki/Home#compatible-status-bars
 [Discord server]: https://discord.gg/jJxZnrGPWN
 [Wayland]: https://wayland.freedesktop.org/
-[#dwl-official:matrix.org]: https://matrix.to/#/#dwl-official:matrix.org
+[#dwl-official:matrix.org]: https://matrix.to/#/#dwl-official:matrix.org

dwl.c

@@ -586,7 +586,7 @@ arrangelayers(Monitor *m)
 		arrange(m);
 	}
 
-	/* Arrange non-exlusive surfaces from top->bottom */
+	/* Arrange non-exclusive surfaces from top->bottom */
 	for (i = 3; i >= 0; i--)
 		arrangelayer(m, &m->layers[i], &usable_area, 0);
 
@@ -1242,6 +1242,7 @@ void
 destroydecoration(struct wl_listener *listener, void *data)
 {
 	Client *c = wl_container_of(listener, c, destroy_decoration);
+	c->decoration = NULL;
 
 	wl_list_remove(&c->destroy_decoration.link);
 	wl_list_remove(&c->set_decoration_mode.link);
@@ -1347,6 +1348,10 @@ destroynotify(struct wl_listener *listener, void *data)
 		wl_list_remove(&c->map.link);
 		wl_list_remove(&c->unmap.link);
 		wl_list_remove(&c->maximize.link);
+		if (c->decoration) {
+			wl_list_remove(&c->set_decoration_mode.link);
+			wl_list_remove(&c->destroy_decoration.link);
+		}
 	}
 	free(c);
 }
@@ -2134,7 +2139,7 @@ powermgrsetmode(struct wl_listener *listener, void *data)
 	if (!m)
 		return;
 
-	m->gamma_lut_changed = 1; /* Reapply gamma LUT when re-enabling the ouput */
+	m->gamma_lut_changed = 1; /* Reapply gamma LUT when re-enabling the output */
 	wlr_output_state_set_enabled(&state, event->mode);
 	wlr_output_commit_state(m->wlr_output, &state);
 
@@ -2456,7 +2461,7 @@ setup(void)
 	wlr_log_init(log_level, NULL);
 
 	/* The Wayland display is managed by libwayland. It handles accepting
-	 * clients from the Unix socket, manging Wayland globals, and so on. */
+	 * clients from the Unix socket, managing Wayland globals, and so on. */
 	dpy = wl_display_create();
 	event_loop = wl_display_get_event_loop(dpy);
 
@@ -2834,6 +2839,7 @@ unmapnotify(struct wl_listener *listener, void *data)
 	}
 
 	wlr_scene_node_destroy(&c->scene->node);
+	client_surface(c)->data = NULL;
 	printstatus();
 	motionnotify(0, NULL, 0, 0, 0, 0);
 }
@@ -2856,10 +2862,13 @@ updatemons(struct wl_listener *listener, void *data)
 
 	/* First remove from the layout the disabled monitors */
 	wl_list_for_each(m, &mons, link) {
-		if (m->wlr_output->enabled || m->asleep)
+		if (m->wlr_output->enabled)
 			continue;
 		config_head = wlr_output_configuration_head_v1_create(config, m->wlr_output);
 		config_head->state.enabled = 0;
+		if (m->asleep)
+			continue;
+
 		/* Remove this output from the layout to avoid cursor enter inside it */
 		wlr_output_layout_remove(output_layout, m->wlr_output);
 		closemon(m);