Merge branch 'signal-emit-final' into 'master'

Draft: util/signal: Introduce wlr_signal_emit_final

See merge request wlroots/wlroots!5061

include/util/signal.h

@@ -0,0 +1,8 @@
+#ifndef UTIL_SIGNAL_H
+#define UTIL_SIGNAL_H
+
+#include <wayland-server-core.h>
+
+void wlr_signal_emit_final(struct wl_signal *signal, void *data);
+
+#endif

types/output/output.c

@@ -11,6 +11,7 @@
 #include "types/wlr_output.h"
 #include "util/env.h"
 #include "util/global.h"
+#include "util/signal.h"
 
 #define OUTPUT_VERSION 4
 
@@ -375,7 +376,7 @@ void wlr_output_init(struct wlr_output *output, struct wlr_backend *backend,
 }
 
 void wlr_output_finish(struct wlr_output *output) {
-	wl_signal_emit_mutable(&output->events.destroy, output);
+	wlr_signal_emit_final(&output->events.destroy, output);
 	wlr_addon_set_finish(&output->addons);
 
 	assert(wl_list_empty(&output->events.frame.listener_list));

util/meson.build

@@ -11,6 +11,7 @@ wlr_files += files(
 	'region.c',
 	'set.c',
 	'shm.c',
+	'signal.c',
 	'time.c',
 	'token.c',
 	'transform.c',

util/signal.c

@@ -0,0 +1,18 @@
+#include "util/signal.h"
+
+void wlr_signal_emit_final(struct wl_signal *signal, void *data) {
+
+	// We need to run all listeners one final time. To support all types of list mutations and to
+	// ensure that all listeners including those added during this execution is run, we run until
+	// the list is empty, removing listeners just before we run them. To not affect the behavior of
+	// the listener, we re-initialize the listener's link element.
+	while (signal->listener_list.next != &signal->listener_list) {
+		struct wl_list *pos = signal->listener_list.next;
+		struct wl_listener *l = wl_container_of(pos, l, link);
+
+		wl_list_remove(pos);
+		wl_list_init(pos);
+
+		l->notify(l, data);
+	}
+}