[MP] Implement "watched" properties (reliable/on change).

modules/multiplayer/doc_classes/MultiplayerSynchronizer.xml

@@ -51,14 +51,17 @@
 		</method>
 	</methods>
 	<members>
+		<member name="delta_interval" type="float" setter="set_delta_interval" getter="get_delta_interval" default="0.0">
+			Time interval between delta synchronizations. When set to [code]0.0[/code] (the default), delta synchronizations happen every network process frame.
+		</member>
 		<member name="public_visibility" type="bool" setter="set_visibility_public" getter="is_visibility_public" default="true">
 			Whether synchronization should be visible to all peers by default. See [method set_visibility_for] and [method add_visibility_filter] for ways of configuring fine-grained visibility options.
 		</member>
 		<member name="replication_config" type="SceneReplicationConfig" setter="set_replication_config" getter="get_replication_config">
 			Resource containing which properties to synchronize.
 		</member>
 		<member name="replication_interval" type="float" setter="set_replication_interval" getter="get_replication_interval" default="0.0">
-			Time interval between synchronizes. When set to [code]0.0[/code] (the default), synchronizes happen every network process frame.
+			Time interval between synchronizations. When set to [code]0.0[/code] (the default), synchronizations happen every network process frame.
 		</member>
 		<member name="root_path" type="NodePath" setter="set_root_path" getter="get_root_path" default="NodePath(&quot;..&quot;)">
 			Node path that replicated properties are relative to.
@@ -69,9 +72,14 @@
 		</member>
 	</members>
 	<signals>
+		<signal name="delta_synchronized">
+			<description>
+				Emitted when a new delta synchronization state is received by this synchronizer after the properties have been updated.
+			</description>
+		</signal>
 		<signal name="synchronized">
 			<description>
-				Emitted when a new synchronization state is received by this synchronizer after the variables have been updated.
+				Emitted when a new synchronization state is received by this synchronizer after the properties have been updated.
 			</description>
 		</signal>
 		<signal name="visibility_changed">

modules/multiplayer/doc_classes/SceneMultiplayer.xml

@@ -70,6 +70,12 @@
 		<member name="auth_timeout" type="float" setter="set_auth_timeout" getter="get_auth_timeout" default="3.0">
 			If set to a value greater than [code]0.0[/code], the maximum amount of time peers can stay in the authenticating state, after which the authentication will automatically fail. See the [signal peer_authenticating] and [signal peer_authentication_failed] signals.
 		</member>
+		<member name="max_delta_packet_size" type="int" setter="set_max_delta_packet_size" getter="get_max_delta_packet_size" default="65535">
+			Maximum size of each delta packet. Higher values increase the chance of receiving full updates in a single frame, but also the chance of causing networking congestion (higher latency, disconnections). See [MultiplayerSynchronizer].
+		</member>
+		<member name="max_sync_packet_size" type="int" setter="set_max_sync_packet_size" getter="get_max_sync_packet_size" default="1350">
+			Maximum size of each synchronization packet. Higher values increase the chance of receiving full updates in a single frame, but also the chance of packet loss. See [MultiplayerSynchronizer].
+		</member>
 		<member name="refuse_new_connections" type="bool" setter="set_refuse_new_connections" getter="is_refusing_new_connections" default="false">
 			If [code]true[/code], the MultiplayerAPI's [member MultiplayerAPI.multiplayer_peer] refuses new incoming connections.
 		</member>

modules/multiplayer/doc_classes/SceneReplicationConfig.xml

@@ -50,6 +50,13 @@
 				Returns whether the property identified by the given [param path] is configured to be synchronized on process.
 			</description>
 		</method>
+		<method name="property_get_watch">
+			<return type="bool" />
+			<param index="0" name="path" type="NodePath" />
+			<description>
+				Returns whether the property identified by the given [code]path[/code] is configured to be reliably synchronized when changes are detected on process.
+			</description>
+		</method>
 		<method name="property_set_spawn">
 			<return type="void" />
 			<param index="0" name="path" type="NodePath" />
@@ -66,6 +73,14 @@
 				Sets whether the property identified by the given [param path] is configured to be synchronized on process.
 			</description>
 		</method>
+		<method name="property_set_watch">
+			<return type="void" />
+			<param index="0" name="path" type="NodePath" />
+			<param index="1" name="enabled" type="bool" />
+			<description>
+				Sets whether the property identified by the given [code]path[/code] is configured to be reliably synchronized when changes are detected on process.
+			</description>
+		</method>
 		<method name="remove_property">
 			<return type="void" />
 			<param index="0" name="path" type="NodePath" />

modules/multiplayer/editor/replication_editor.cpp

@@ -226,7 +226,7 @@ ReplicationEditor::ReplicationEditor() {
 
 	tree = memnew(Tree);
 	tree->set_hide_root(true);
-	tree->set_columns(4);
+	tree->set_columns(5);
 	tree->set_column_titles_visible(true);
 	tree->set_column_title(0, TTR("Properties"));
 	tree->set_column_expand(0, true);
@@ -235,8 +235,11 @@ ReplicationEditor::ReplicationEditor() {
 	tree->set_column_custom_minimum_width(1, 100);
 	tree->set_column_title(2, TTR("Sync"));
 	tree->set_column_custom_minimum_width(2, 100);
+	tree->set_column_title(3, TTR("Watch"));
+	tree->set_column_custom_minimum_width(3, 100);
 	tree->set_column_expand(2, false);
 	tree->set_column_expand(3, false);
+	tree->set_column_expand(4, false);
 	tree->create_item();
 	tree->connect("button_clicked", callable_mp(this, &ReplicationEditor::_tree_button_pressed));
 	tree->connect("item_edited", callable_mp(this, &ReplicationEditor::_tree_item_edited));
@@ -353,17 +356,30 @@ void ReplicationEditor::_tree_item_edited() {
 		return;
 	}
 	int column = tree->get_edited_column();
-	ERR_FAIL_COND(column < 1 || column > 2);
+	ERR_FAIL_COND(column < 1 || column > 3);
 	const NodePath prop = ti->get_metadata(0);
 	EditorUndoRedoManager *undo_redo = EditorUndoRedoManager::get_singleton();
 	bool value = ti->is_checked(column);
+
+	// We have a hard limit of 64 watchable properties per synchronizer.
+	if (column == 3 && value && config->get_watch_properties().size() > 64) {
+		error_dialog->set_text(TTR("Each MultiplayerSynchronizer can have no more than 64 watched properties."));
+		error_dialog->popup_centered();
+		ti->set_checked(column, false);
+		return;
+	}
 	String method;
 	if (column == 1) {
 		undo_redo->create_action(TTR("Set spawn property"));
 		method = "property_set_spawn";
-	} else {
+	} else if (column == 2) {
 		undo_redo->create_action(TTR("Set sync property"));
 		method = "property_set_sync";
+	} else if (column == 3) {
+		undo_redo->create_action(TTR("Set watch property"));
+		method = "property_set_watch";
+	} else {
+		ERR_FAIL();
 	}
 	undo_redo->add_do_method(config.ptr(), method, prop, value);
 	undo_redo->add_undo_method(config.ptr(), method, prop, !value);
@@ -395,12 +411,14 @@ void ReplicationEditor::_dialog_closed(bool p_confirmed) {
 		int idx = config->property_get_index(prop);
 		bool spawn = config->property_get_spawn(prop);
 		bool sync = config->property_get_sync(prop);
+		bool watch = config->property_get_watch(prop);
 		EditorUndoRedoManager *undo_redo = EditorUndoRedoManager::get_singleton();
 		undo_redo->create_action(TTR("Remove Property"));
 		undo_redo->add_do_method(config.ptr(), "remove_property", prop);
 		undo_redo->add_undo_method(config.ptr(), "add_property", prop, idx);
 		undo_redo->add_undo_method(config.ptr(), "property_set_spawn", prop, spawn);
 		undo_redo->add_undo_method(config.ptr(), "property_set_sync", prop, sync);
+		undo_redo->add_undo_method(config.ptr(), "property_set_watch", prop, watch);
 		undo_redo->add_do_method(this, "_update_config");
 		undo_redo->add_undo_method(this, "_update_config");
 		undo_redo->commit_action();
@@ -436,7 +454,7 @@ void ReplicationEditor::_update_config() {
 	}
 	for (int i = 0; i < props.size(); i++) {
 		const NodePath path = props[i];
-		_add_property(path, config->property_get_spawn(path), config->property_get_sync(path));
+		_add_property(path, config->property_get_spawn(path), config->property_get_sync(path), config->property_get_watch(path));
 	}
 }
 
@@ -460,13 +478,14 @@ Ref<Texture2D> ReplicationEditor::_get_class_icon(const Node *p_node) {
 	return get_theme_icon(p_node->get_class(), "EditorIcons");
 }
 
-void ReplicationEditor::_add_property(const NodePath &p_property, bool p_spawn, bool p_sync) {
+void ReplicationEditor::_add_property(const NodePath &p_property, bool p_spawn, bool p_sync, bool p_watch) {
 	String prop = String(p_property);
 	TreeItem *item = tree->create_item();
 	item->set_selectable(0, false);
 	item->set_selectable(1, false);
 	item->set_selectable(2, false);
 	item->set_selectable(3, false);
+	item->set_selectable(4, false);
 	item->set_text(0, prop);
 	item->set_metadata(0, prop);
 	Node *root_node = current && !current->get_root_path().is_empty() ? current->get_node(current->get_root_path()) : nullptr;
@@ -482,7 +501,7 @@ void ReplicationEditor::_add_property(const NodePath &p_property, bool p_spawn,
 		icon = _get_class_icon(node);
 	}
 	item->set_icon(0, icon);
-	item->add_button(3, get_theme_icon(SNAME("Remove"), SNAME("EditorIcons")));
+	item->add_button(4, get_theme_icon(SNAME("Remove"), SNAME("EditorIcons")));
 	item->set_text_alignment(1, HORIZONTAL_ALIGNMENT_CENTER);
 	item->set_cell_mode(1, TreeItem::CELL_MODE_CHECK);
 	item->set_checked(1, p_spawn);
@@ -491,4 +510,8 @@ void ReplicationEditor::_add_property(const NodePath &p_property, bool p_spawn,
 	item->set_cell_mode(2, TreeItem::CELL_MODE_CHECK);
 	item->set_checked(2, p_sync);
 	item->set_editable(2, true);
+	item->set_text_alignment(3, HORIZONTAL_ALIGNMENT_CENTER);
+	item->set_cell_mode(3, TreeItem::CELL_MODE_CHECK);
+	item->set_checked(3, p_watch);
+	item->set_editable(3, true);
 }

modules/multiplayer/editor/replication_editor.h

@@ -76,7 +76,7 @@ class ReplicationEditor : public VBoxContainer {
 	void _update_checked(const NodePath &p_prop, int p_column, bool p_checked);
 	void _update_config();
 	void _dialog_closed(bool p_confirmed);
-	void _add_property(const NodePath &p_property, bool p_spawn = true, bool p_sync = true);
+	void _add_property(const NodePath &p_property, bool p_spawn = true, bool p_sync = true, bool p_watch = false);
 
 	void _pick_node_filter_text_changed(const String &p_newtext);
 	void _pick_node_select_recursive(TreeItem *p_item, const String &p_filter, Vector<Node *> &p_select_candidates);

modules/multiplayer/multiplayer_synchronizer.cpp

@@ -105,7 +105,7 @@ Node *MultiplayerSynchronizer::get_root_node() {
 
 void MultiplayerSynchronizer::reset() {
 	net_id = 0;
-	last_sync_msec = 0;
+	last_sync_usec = 0;
 	last_inbound_sync = 0;
 }
 
@@ -117,16 +117,17 @@ void MultiplayerSynchronizer::set_net_id(uint32_t p_net_id) {
 	net_id = p_net_id;
 }
 
-bool MultiplayerSynchronizer::update_outbound_sync_time(uint64_t p_msec) {
-	if (last_sync_msec == p_msec) {
-		// last_sync_msec has been updated on this frame.
+bool MultiplayerSynchronizer::update_outbound_sync_time(uint64_t p_usec) {
+	if (last_sync_usec == p_usec) {
+		// last_sync_usec has been updated in this frame.
 		return true;
 	}
-	if (p_msec >= last_sync_msec + interval_msec) {
-		last_sync_msec = p_msec;
-		return true;
+	if (p_usec < last_sync_usec + sync_interval_usec) {
+		// Too soon, should skip this synchronization frame.
+		return false;
 	}
-	return false;
+	last_sync_usec = p_usec;
+	return true;
 }
 
 bool MultiplayerSynchronizer::update_inbound_sync_time(uint16_t p_network_time) {
@@ -243,6 +244,9 @@ void MultiplayerSynchronizer::_bind_methods() {
 	ClassDB::bind_method(D_METHOD("set_replication_interval", "milliseconds"), &MultiplayerSynchronizer::set_replication_interval);
 	ClassDB::bind_method(D_METHOD("get_replication_interval"), &MultiplayerSynchronizer::get_replication_interval);
 
+	ClassDB::bind_method(D_METHOD("set_delta_interval", "milliseconds"), &MultiplayerSynchronizer::set_delta_interval);
+	ClassDB::bind_method(D_METHOD("get_delta_interval"), &MultiplayerSynchronizer::get_delta_interval);
+
 	ClassDB::bind_method(D_METHOD("set_replication_config", "config"), &MultiplayerSynchronizer::set_replication_config);
 	ClassDB::bind_method(D_METHOD("get_replication_config"), &MultiplayerSynchronizer::get_replication_config);
 
@@ -260,6 +264,7 @@ void MultiplayerSynchronizer::_bind_methods() {
 
 	ADD_PROPERTY(PropertyInfo(Variant::NODE_PATH, "root_path"), "set_root_path", "get_root_path");
 	ADD_PROPERTY(PropertyInfo(Variant::FLOAT, "replication_interval", PROPERTY_HINT_RANGE, "0,5,0.001,suffix:s"), "set_replication_interval", "get_replication_interval");
+	ADD_PROPERTY(PropertyInfo(Variant::FLOAT, "delta_interval", PROPERTY_HINT_RANGE, "0,5,0.001,suffix:s"), "set_delta_interval", "get_delta_interval");
 	ADD_PROPERTY(PropertyInfo(Variant::OBJECT, "replication_config", PROPERTY_HINT_RESOURCE_TYPE, "SceneReplicationConfig", PROPERTY_USAGE_NO_EDITOR), "set_replication_config", "get_replication_config");
 	ADD_PROPERTY(PropertyInfo(Variant::INT, "visibility_update_mode", PROPERTY_HINT_ENUM, "Idle,Physics,None"), "set_visibility_update_mode", "get_visibility_update_mode");
 	ADD_PROPERTY(PropertyInfo(Variant::BOOL, "public_visibility"), "set_visibility_public", "is_visibility_public");
@@ -269,6 +274,7 @@ void MultiplayerSynchronizer::_bind_methods() {
 	BIND_ENUM_CONSTANT(VISIBILITY_PROCESS_NONE);
 
 	ADD_SIGNAL(MethodInfo("synchronized"));
+	ADD_SIGNAL(MethodInfo("delta_synchronized"));
 	ADD_SIGNAL(MethodInfo("visibility_changed", PropertyInfo(Variant::INT, "for_peer")));
 }
 
@@ -300,11 +306,20 @@ void MultiplayerSynchronizer::_notification(int p_what) {
 
 void MultiplayerSynchronizer::set_replication_interval(double p_interval) {
 	ERR_FAIL_COND_MSG(p_interval < 0, "Interval must be greater or equal to 0 (where 0 means default)");
-	interval_msec = uint64_t(p_interval * 1000);
+	sync_interval_usec = uint64_t(p_interval * 1000 * 1000);
 }
 
 double MultiplayerSynchronizer::get_replication_interval() const {
-	return double(interval_msec) / 1000.0;
+	return double(sync_interval_usec) / 1000.0 / 1000.0;
+}
+
+void MultiplayerSynchronizer::set_delta_interval(double p_interval) {
+	ERR_FAIL_COND_MSG(p_interval < 0, "Interval must be greater or equal to 0 (where 0 means default)");
+	delta_interval_usec = uint64_t(p_interval * 1000 * 1000);
+}
+
+double MultiplayerSynchronizer::get_delta_interval() const {
+	return double(delta_interval_usec) / 1000.0 / 1000.0;
 }
 
 void MultiplayerSynchronizer::set_replication_config(Ref<SceneReplicationConfig> p_config) {
@@ -349,6 +364,84 @@ void MultiplayerSynchronizer::set_multiplayer_authority(int p_peer_id, bool p_re
 	get_multiplayer()->object_configuration_add(node, this);
 }
 
+Error MultiplayerSynchronizer::_watch_changes(uint64_t p_usec) {
+	ERR_FAIL_COND_V(replication_config.is_null(), FAILED);
+	const List<NodePath> props = replication_config->get_watch_properties();
+	if (props.size() != watchers.size()) {
+		watchers.resize(props.size());
+	}
+	if (props.size() == 0) {
+		return OK;
+	}
+	Node *node = get_root_node();
+	ERR_FAIL_COND_V(!node, FAILED);
+	int idx = -1;
+	Watcher *ptr = watchers.ptrw();
+	for (const NodePath &prop : props) {
+		idx++;
+		bool valid = false;
+		const Object *obj = _get_prop_target(node, prop);
+		ERR_CONTINUE_MSG(!obj, vformat("Node not found for property '%s'.", prop));
+		Variant v = obj->get(prop.get_concatenated_subnames(), &valid);
+		ERR_CONTINUE_MSG(!valid, vformat("Property '%s' not found.", prop));
+		Watcher &w = ptr[idx];
+		if (w.prop != prop) {
+			w.prop = prop;
+			w.value = v.duplicate(true);
+			w.last_change_usec = p_usec;
+		} else if (!w.value.hash_compare(v)) {
+			w.value = v.duplicate(true);
+			w.last_change_usec = p_usec;
+		}
+	}
+	return OK;
+}
+
+List<Variant> MultiplayerSynchronizer::get_delta_state(uint64_t p_cur_usec, uint64_t p_last_usec, uint64_t &r_indexes) {
+	r_indexes = 0;
+	List<Variant> out;
+
+	if (last_watch_usec == p_cur_usec) {
+		// We already watched for changes in this frame.
+
+	} else if (p_cur_usec < p_last_usec + delta_interval_usec) {
+		// Too soon skip delta synchronization.
+		return out;
+
+	} else {
+		// Watch for changes.
+		Error err = _watch_changes(p_cur_usec);
+		ERR_FAIL_COND_V(err != OK, out);
+		last_watch_usec = p_cur_usec;
+	}
+
+	const Watcher *ptr = watchers.size() ? watchers.ptr() : nullptr;
+	for (int i = 0; i < watchers.size(); i++) {
+		const Watcher &w = ptr[i];
+		if (w.last_change_usec <= p_last_usec) {
+			continue;
+		}
+		out.push_back(w.value);
+		r_indexes |= 1ULL << i;
+	}
+	return out;
+}
+
+List<NodePath> MultiplayerSynchronizer::get_delta_properties(uint64_t p_indexes) {
+	List<NodePath> out;
+	ERR_FAIL_COND_V(replication_config.is_null(), out);
+	const List<NodePath> watch_props = replication_config->get_watch_properties();
+	int idx = 0;
+	for (const NodePath &prop : watch_props) {
+		if ((p_indexes & (1ULL << idx)) == 0) {
+			continue;
+		}
+		out.push_back(prop);
+		idx++;
+	}
+	return out;
+}
+
 MultiplayerSynchronizer::MultiplayerSynchronizer() {
 	// Publicly visible by default.
 	peer_visibility.insert(0);