Pressing this key cycles through the layouts assigned to keyboard's LayoutRing property. The key's default appearance is determined by the properties of the *next* layout in the LayoutRing cycle, following this priority:

1.  If the next layout has a non-null / empty Image property, that image is displayed.
2.  If there is no Image assigned to the layout, but the Label property is set, that text is displayed as key's Content.
3.  If neither Image nor Label is set, the key will display the Unicode keyboard symbol (U+2328) as a fallback.

You can change these rules by setting a custom Xaml data template for the LayoutRingKey type.

System.Object
    MindFusion.UI.Wpf.Key
        MindFusion.UI.Wpf.LayoutRingKey

LayoutRingKey Members
MindFusion.UI.Wpf Namespace