Holy Light

Holy Light by Samy Dindane is a plugin for Macs that changes the background variable based on the amount of ambient light recorded by Mac's light sensor.

The sensor is interrogated using a binary program, the source of which can be found here: holylight-checker.mm. The program works by connecting to Apple’s LMU I/O service (AppleLMUController), and then grabbing the current brightness value. If the value is less than a threshold (1000000) then the background is switched to dark.

The 'background' value can be set manually with :set background=light and :set background=dark (:help 'background', abbreviation: bg). Vim tries to pick colours that will look good on a dark/light background.