Added a dynamic layout system where UI elements can be moved about on a tiled grid.

scripts/layout_library.gd

@@ -0,0 +1,30 @@
+extends PanelContainer
+
+signal element_requested(element_type: String)
+const CATALOG = preload("res://scripts/layout_catalog.gd")
+var _types: Array = []
+
+func _ready() -> void:
+	_types = CATALOG.ENTRIES.keys()
+	for element_type in _types:
+		$Margin/Body/List.add_item(CATALOG.ENTRIES[element_type].title)
+	$Margin/Body/List.item_selected.connect(_select)
+	$Margin/Body/List.item_activated.connect(func(_index: int) -> void: _request())
+	$Margin/Body/Add.pressed.connect(_request)
+	$Margin/Body/Header/Close.pressed.connect(hide)
+	$Margin/Body/List.select(0)
+	_select(0)
+
+func _select(index: int) -> void:
+	var entry: Dictionary = CATALOG.ENTRIES[_types[index]]
+	$Margin/Body/Description.text = entry.description
+	$Margin/Body/Size.text = "%d × %d cells · minimum %d × %d" % [entry.size.x, entry.size.y, entry.minimum.x, entry.minimum.y]
+	$Margin/Body/Status.text = ""
+
+func _request() -> void:
+	var indices: PackedInt32Array = $Margin/Body/List.get_selected_items()
+	if not indices.is_empty():
+		element_requested.emit(_types[indices[0]])
+
+func show_no_space() -> void:
+	$Margin/Body/Status.text = "No space available. Move, resize or remove a panel first."