godot/doc/classes/PopupPanel.xml

<?xml version="1.0" encoding="UTF-8" ?>
<class name="PopupPanel" inherits="Popup" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="../class.xsd">
	<brief_description>
		A popup with a panel background.
	</brief_description>
	<description>
		A popup with a configurable panel background. Any child controls added to this node will be stretched to fit the panel's size (similar to how [PanelContainer] works). If you are making windows, see [Window].
	</description>
	<tutorials>
	</tutorials>
	<theme_items>
		<theme_item name="panel" data_type="style" type="StyleBox">
			[StyleBox] for the background panel.
		</theme_item>
	</theme_items>
</class>