Smooth external monitor brightness control (assignable to keyboard shortcuts)

brightness.rb

#!/usr/bin/env ruby
# frozen_string_literal: true

mon = 'DP-1'     # Discover monitor name with: xrandr | grep " connected"
total_inc = 0.20 # Step Up/Down brightness by inc
steps = 10       # Total number of steps (for gradient)

# Avoid reentrance which would cause jerky behavior
exit 0 if Integer(`ps aux | grep "ruby #{__FILE__}" | wc -l`) > 3

# Get brightness level with decimal place
curr_brightness = Float(`xrandr --verbose --current | grep ^"#{mon}" -A5 | tail -n1`.split(':').last)

case ARGV.first&.downcase
when '+', 'up'
  factor = 1
when '-', 'down'
  factor = -1
end
target_brightness = (curr_brightness + (factor * total_inc)).clamp(0.1, 1.0) if factor

if target_brightness
  inc = ((target_brightness - curr_brightness) / steps).round(2)

  (1..steps).each do
    break if curr_brightness == target_brightness

    curr_brightness = (curr_brightness + inc).clamp(0.1, 1.0).round(2)
    # Set new brightness
    `xrandr --output "#{mon}" --brightness "#{curr_brightness}"`
  end
end

# Display current brightness
puts "Monitor #{mon} "
puts `xrandr --verbose --current | grep ^"#{mon}" -A5 | tail -n1`

Keyboard shortcut:

/home/pedro/.rbenv/shims/ruby /usr/local/bin/brightness.rb Down