Major clean up and reorganization

- Upgraded to Godot 4
- Just remembered the basic principles are based on a tile editor, and dramatically simplified from there. Derp.
- New state machine and license display add-ons.
- Re-licensed under the GPL because Micropolis' assets aren't under a separate one.

addons/simple-state/classes/debugger.gd

@@ -0,0 +1,139 @@
+@icon("../icons/state_machine_debugger.png")
+class_name StateMachineDebugger
+extends Tree
+
+
+## Displays an interactive state tree.
+# This source code is a mess, I'm trying to make it less so.
+
+
+@export
+## Root state machine to reference.
+var state_machine_root : State:
+	set(value):
+		state_machine_root = value
+		_setup_tree()
+
+@export
+## What color to make the item when a state is active.
+var active_color := Color.FOREST_GREEN
+
+@export
+## Forcefully switch states by double-clicking them.
+## Due to its nature, it has the potential to be destructive
+## and/ or not behave completely how one might expect.
+var allow_state_switching := false:
+	set(value):
+		allow_state_switching = value
+		if allow_state_switching:
+			item_activated.connect(_on_item_activated)
+		else:
+			item_activated.disconnect(_on_item_activated)
+
+
+@export_group("Signals", "signal_")
+@export
+## Show when a state emits a relevant signal.
+var signal_show := false:
+	set(value):
+		signal_show = value
+		
+		if state_machine_root == null:
+			return
+		
+		if signal_show:
+			connect_signals()
+		else:
+			disconnect_signals()
+
+@export
+## Which signals to connect to on each state, as long as they exist.
+var signal_connections : Array[StringName] = [
+	&"entered",
+	&"exited",
+	&"choose_new_substate_requested",
+	&"animation_finished",
+]
+
+@export
+## Delay before hiding signal.
+var signal_hide_delay := 1.0
+
+
+func _init() -> void:
+	columns = 2
+
+
+func change_state_by_path(path: NodePath) -> void:
+	if not state_machine_root.has_node(path):
+		return
+	var state := state_machine_root
+	for i in path.get_name_count():
+		var part := path.get_name(i)
+		state = await state.change_state_name(part)
+
+
+func connect_signals(state := state_machine_root) -> void:
+	if not state.has_meta(&"tree_item"):
+		return
+	for signal_name in signal_connections:
+		if state.has_signal(signal_name) and not \
+				state.is_connected(signal_name, _on_state_signal):
+			state.connect(signal_name, _on_state_signal.bind(signal_name, state.get_meta(&"tree_item")))
+	for child in(state.get_children() as Array[State]):
+		connect_signals(child)
+
+
+func disconnect_signals(state := state_machine_root) -> void:
+	for signal_name in signal_connections:
+		if state.has_signal(signal_name) and \
+				state.is_connected(signal_name, _on_state_signal):
+			state.disconnect(signal_name, _on_state_signal)
+	for child in (state.get_children() as Array[State]):
+		disconnect_signals(child)
+
+
+func _setup_tree(state := state_machine_root, parent_item: TreeItem = null) -> void:
+	if state == state_machine_root:
+		if get_root() != null:
+			disconnect_signals()
+		clear()
+		if state_machine_root == null:
+			return
+#		state.print_tree_pretty()
+	
+	# TODO: add icons
+	var item := create_item(parent_item)
+	item.set_text(0, state.name)
+	item.set_metadata(0, state)
+	state.set_meta(&"tree_item", item)
+	connect_signals(state)
+	
+	for child in (state.get_children() as Array[State]):
+		_setup_tree(child, item)
+
+
+func _on_item_activated() -> void:
+	change_state_by_path(state_machine_root.get_path_to(
+			get_selected().get_metadata(0) as State))
+
+
+func _on_state_signal(signal_name: StringName, state_item: TreeItem) -> void:
+	match signal_name:
+		&"entered":
+			for i in columns:
+				state_item.set_custom_color(i, active_color)
+		&"exited":
+			for i in columns:
+				state_item.clear_custom_color(i)
+	
+	if not signal_show:
+		return
+	
+	state_item.set_text(1, signal_name)
+	var timer := state_item.get_metadata(1) as SceneTreeTimer
+	if timer != null:
+		timer.timeout.disconnect(state_item.set_text)
+	timer = get_tree().create_timer(signal_hide_delay)
+	timer.timeout.connect(state_item.set_text.bind(1, ""))
+	state_item.set_metadata(1, timer)