File with name window.xml is default configuration file for theme background images. Also can be other xml files with same format for different windows.

<skinset name="Default" image="window.png">
	<widget type="Window" xpos="68" ypos="75">
		<option name="padding" value="5" /> 

		<!-- Top Row -->
		<part type="top-left-corner" xpos="0" ypos="0" width="4" height="4" />
		<part type="top-edge" xpos="4" ypos="0" width="32" height="4" />
		<part type="top-right-corner" xpos="36" ypos="0" width="4" height="4" />

		<!-- Middle Row -->
		<part type="left-edge" xpos="0" ypos="4" width="4" height="216" />
		<part type="bg-quad" xpos="4" ypos="4" width="32" height="216" />
		<part type="right-edge" xpos="36" ypos="4" width="4" height="216" />

		<!-- Bottom Row -->
		<part type="bottom-left-corner" xpos="0" ypos="220" width="4" height="4" />
		<part type="bottom-edge" xpos="4" ypos="220" width="32" height="4" />
		<part type="bottom-right-corner" xpos="36" ypos="220" width="4" height="4" />
	</widget>
</skinset>

<skinset name="Default" image="window.png">

Here is set image for background. In this example it’s window.png

<widget type="Window" xpos="68" ypos="75">

This tag start window widget. xpos and ypos optional, if missed it equip 0. xpos and ypos used for global offset for any positions.

<option name="padding" value="5" />

This tag set padding in pixels. Tag optional.

<part type="top-left-corner" xpos="0" ypos="0" width="4" height="4" />

Set image for top left window corner

<part type="top-edge" xpos="4" ypos="0" width="32" height="4" />

Set image for top border.

<part type="top-right-corner" xpos="36" ypos="0" width="4" height="4" />

Set image for top right corner.

<part type="left-edge" xpos="0" ypos="4" width="4" height="216" />

Set image for left border.

<part type="bg-quad" xpos="4" ypos="4" width="32" height="216" />

Set image for center background.

<part type="right-edge" xpos="36" ypos="4" width="4" height="216" />

Set image for right border.

<part type="bottom-left-corner" xpos="0" ypos="220" width="4" height="4" />

Set image for bottom left corner

<part type="bottom-edge" xpos="4" ypos="220" width="32" height="4" />

Set image for bottom border

<part type="bottom-right-corner" xpos="36" ypos="220" width="4" height="4" />

Set image for bottom right corner.

themes, windows, themes files