macOS screen dimmer spoon

A Lua "spoon" script for Hammerspoon to dim MacBook Pro's internal screen and any external DDC-compatible monitors to a preset luminosity (10% by default) after a preset period of inactivity (5 minutes by default) has elapsed.

NOTE: This new version has been rewritten to use Lunar Pro CLI utility, lunar. As a result, this script now supports all DDC-capable monitors. Some additional features have also been implemented, as outlined below.

• The gamma mode ("subzero") is supported via Lunar's capability. dimLevel values 1-100 correspond to the hardware-based brightness, whereas values -1 through -100 correspond to the gamma shader values.
• The optional internalDisplayGainLevel sets the MacBook Pro's internal display to a different dimness level from the external monitor(s). You can define a positive or negative value. However, a positive value is usually used because the internal display tends to appear darker than external monitors at the same dimLevel.
• Optional displayPriorities can be defined to change the default order in which the displays are dimmed and restored. The sequence happens quickly, but you may nevertheless want your primary monitor dimmed/restored first.
• Automatic handling of connected/disconnected monitors without having to reload the spoon.

I use this script when I don't want to use the screen saver and/or screen sleep, but I also don't want to keep the screen at normal brightness when I don't actively use the system. The original brightness is restored upon the first user interaction (keyboard/mouse/trackpad). The script handles brightness restoration correctly after the screen saver, lock screen, and screen sleep.

Installation

First, make sure you have Lunar Pro installed and then select from its toolbar menu: Advanced Features → Install CLI integration. This will install the lunar CLI utility at ~/.local/bin/lunar

If you don't want to use Lunar Pro's CLI utility, switch to the m1ddc-based branch (after cloning the repository as outlined below, change to the ScreenDimmer.spoon directory and execute git checkout --track origin/m1ddc-based. This branch works with m1ddc, a FOSS utility (install with brew install m1ddc). Note: The old m1ddc-based version works fine but has fewer features and doesn't support as many DDC-capable monitors (see README.md in that branch for further details).

Make sure you have Hammerspoon installed, then clone this repository in the Spoons directory:

cd ~/.hammerspoon
mkdir Spoons
cd Spoons
git clone https://github.com/vwal/ScreenDimmer.spoon.git

The ScreenDimmer will appear as ScreenDimmer.spoon directory (as Hammerspoon requires).

Call/initialize ScreenDimmer from ~/.hammerspoon/init.lua as shown below:

-- Load ScreenDimmer Spoon
local dimmer = hs.loadSpoon("ScreenDimmer")

-- Configure the Spoon
dimmer:configure({
    idleTimeout = 300,  -- 5 minutes in seconds, adjust as needed
    dimLevel = -75,     -- negative values use "subzero", i.e. gamma shader
    logging = false,    -- set to `true` for debug logging
    lunarPath = "~/.local/bin/lunar", -- optional variable to set the location of the `lunar`
                                      -- CLI command if it's at a non-standard location
    internalDisplayGainLevel = 50,    -- optional variable to dim the internal display to
                                      -- a different level than what is set with `dimLevel`.
                                      -- In this example to -25.
    displayPriorities = {  -- example optional monitor priorities to alter the default
                           -- order of brightness adjustment; get your monitor names
                           -- with `lunar displays`
        ["Built-in"] = 1,
        ["BenQ PD3225U"] = 2,
        ["LG Ultra HD"] = 3
    }
}):start()

-- Bind hotkey
dimmer:bindHotkeys({
    toggle = { {"shift", "cmd", "alt", "ctrl"}, "D" },  -- Enable/disable the dimmer
    dim = { {"shift", "cmd", "alt"}, "D" }              -- Immediate dim toggle
})

Above, I've set a hyperkey+D to toggle the dimmer on/off and ⇧⎇⌘+D to dim the screen(s) immediately (note: you can define both, either or no hotkeys). If no hotkeys are defined when calling ScreenDimmer, none are set internally.

Tested with macOS Sequoia and Hammerspoon 1.0.0. Provided without guarantees (= use at your own risk).

MIT license.