Ayatana Indicator showing power state

 This Ayatana Indicator displays current power management information and
 gives the user a way to access power management preferences.
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 The Ayatana Indicator provides a generic, multi-desktop-env aware
 approach of accessing power information and management features.
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 Ayatana Indicators are only available on desktop environments that
 provide a renderer for system indicators (such as MATE, Xfce, Lomiri,
 etc.).