This component manages the screen backlight. It has two modes auto-brightness and manual.
This interface will typically be used by the brightness UI but will support concurrent users.
In this mode the brightness polls the light sensor and sets the backlight as appropriate, darker as the sensor gets less light and brighter as it gets more.
In manual mode the backlight remains at a fixed brightness until the brightness component is told to set the backlight to another brightness or auto-brightness mode is turned on.
The brightness component always ensures that the screen backlight changes smoothly over short period of time. This means that the calling application can abruptly change the screen brightness without having to worry about making the user jump!
The FIDL interface fuchsia.settings.display is used by the settings component to tell it what to do. The settings component will use this interface to controll brightness.