object: add freeing signal

core/core_string_names.h

@@ -84,6 +84,7 @@ public:
 	const StringName bind = StaticCString::create("bind");
 	const StringName notification = StaticCString::create("notification");
 	const StringName property_list_changed = StaticCString::create("property_list_changed");
+	const StringName freeing = StaticCString::create("freeing");
 };
 
 #define CoreStringName(m_name) CoreStringNames::get_singleton()->m_name

core/object/object.cpp

@@ -228,6 +228,9 @@ Object::Connection::Connection(const Variant &p_variant) {
 bool Object::_predelete() {
 	_predelete_ok = 1;
 	notification(NOTIFICATION_PREDELETE, true);
+	if (_emit_free && _predelete_ok) {
+		emit_signal(CoreStringName(freeing)); // Emit signal early so cancel_free can still occur.
+	}
 	if (_predelete_ok) {
 		_class_name_ptr = nullptr; // Must restore, so constructors/destructors have proper class name access at each stage.
 		notification(NOTIFICATION_PREDELETE_CLEANUP, true);
@@ -1765,12 +1768,14 @@ void Object::_bind_methods() {
 	ClassDB::bind_method(D_METHOD("set_translation_domain", "domain"), &Object::set_translation_domain);
 
 	ClassDB::bind_method(D_METHOD("is_queued_for_deletion"), &Object::is_queued_for_deletion);
+	ClassDB::bind_method(D_METHOD("set_emit_freeing", "enable"), &Object::set_emit_freeing);
 	ClassDB::bind_method(D_METHOD("cancel_free"), &Object::cancel_free);
 
 	ClassDB::add_virtual_method("Object", MethodInfo("free"), false);
 
 	ADD_SIGNAL(MethodInfo("script_changed"));
 	ADD_SIGNAL(MethodInfo("property_list_changed"));
+	ADD_SIGNAL(MethodInfo("freeing"));
 
 #define BIND_OBJ_CORE_METHOD(m_method) \
 	::ClassDB::add_virtual_method(get_class_static(), m_method, true, Vector<String>(), true);
@@ -1930,6 +1935,10 @@ bool Object::is_queued_for_deletion() const {
 	return _is_queued_for_deletion;
 }
 
+void Object::set_emit_freeing(bool p_emit) {
+	_emit_free = p_emit;
+}
+
 #ifdef TOOLS_ENABLED
 void Object::set_edited(bool p_edited) {
 	_edited = p_edited;

core/object/object.h

@@ -628,6 +628,7 @@ private:
 	SafeRefCount _lock_index;
 #endif
 	bool _block_signals = false;
+	bool _emit_free = false;
 	int _predelete_ok = 0;
 	ObjectID _instance_id;
 	bool _predelete();
@@ -998,6 +999,7 @@ public:
 
 	_ALWAYS_INLINE_ bool is_ref_counted() const { return type_is_reference; }
 
+	void set_emit_freeing(bool p_emit);
 	void cancel_free();
 
 	Object();

doc/classes/Object.xml

@@ -1036,6 +1036,13 @@
 				[b]Note:[/b] In C#, [param property] must be in snake_case when referring to built-in Godot properties. Prefer using the names exposed in the [code]PropertyName[/code] class to avoid allocating a new [StringName] on each call.
 			</description>
 		</method>
+		<method name="set_emit_freeing">
+			<return type="void" />
+			<param index="0" name="enable" type="bool" />
+			<description>
+				If set to [code]true[/code], the object will emit [signal freeing] upon cleanup.
+			</description>
+		</method>
 		<method name="set_indexed">
 			<return type="void" />
 			<param index="0" name="property_path" type="NodePath" />
@@ -1126,6 +1133,12 @@
 		</method>
 	</methods>
 	<signals>
+		<signal name="freeing">
+			<description>
+				Emitted when the object is about to be freed. Only emitted after [method set_emit_freeing] is called.
+				This signal is emitted [i]after[/i] the related [constant NOTIFICATION_PREDELETE] notification.
+			</description>
+		</signal>
 		<signal name="property_list_changed">
 			<description>
 				Emitted when [method notify_property_list_changed] is called.