src/hbcore/resources/themes/style/hbdefault/rules/widgets/hbnavigationbutton/hbnavigationbutton.widgetml
<hbwidget version="0.1" type="HbNavigationButton">
<layout name="navigationbuttonlayout" type="mesh">
<meshitem src="background" srcEdge="TOP" dst="" dstEdge="TOP" />
<meshitem src="background" srcEdge="BOTTOM" dst="" dstEdge="BOTTOM" />
<meshitem src="background" srcEdge="LEFT" dst="" dstEdge="LEFT" />
<meshitem src="background" srcEdge="RIGHT" dst="" dstEdge="RIGHT" />
<meshitem src="icon" srcEdge="CENTERV" dst="" dstEdge="CENTERV" />
<meshitem src="icon" srcEdge="CENTERH" dst="" dstEdge="CENTERH" />
<meshitem src="text" srcEdge="CENTERV" dst="" dstEdge="CENTERV" />
<meshitem src="text" srcEdge="CENTERH" dst="" dstEdge="CENTERH" />
<meshitem src="toucharea" srcEdge="TOP" dst="" dstEdge="TOP" />
<meshitem src="toucharea" srcEdge="LEFT" dst="" dstEdge="LEFT" />
<meshitem src="toucharea" srcEdge="RIGHT" dst="" dstEdge="RIGHT" />
</layout>
</hbwidget>