basic ECS spawner

addons/gecs/lib/system_group.gd

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+## This is a node that automatically fills in the [member System.group] property
+## of any [System] that is a child of this node.
+## Allowing you to visually organize your systems in the scene tree
+## without having to manually set the group property on each [System].
+## Add this node to your scene tree and make [System]s children of it.
+## The name of the SystemGroup node will be set to [member System.group] for
+## all child [System]s.
+@tool
+@icon('res://addons/gecs/assets/system_folder.svg')
+class_name SystemGroup
+extends Node
+
+## Put the [System]s in the group based on the [member Node.name] of the [SystemGroup]
+@export var auto_group := true
+
+
+## called when the node enters the scene tree for the first time.
+func _enter_tree() -> void:
+	# Connect signals
+	if not child_entered_tree.is_connected(_on_child_entered_tree):
+		child_entered_tree.connect(_on_child_entered_tree)
+
+	# Set the group for all child systems
+	if auto_group:
+		for child in get_children():
+			if child is System:
+				child.group = name
+
+
+## Anytime  a child enters the tree, set its group if it's a System
+func _on_child_entered_tree(node: Node) -> void:
+	if auto_group:
+		if node is System:
+			node.group = name