Appearance Watcher for macOS

This is a simple utility that allows you to run a custom script whenever the appearance in macOS changes.

For example, I like to update my kitty theme and change my tmux background:

#!/bin/zsh
export PATH="/Applications/kitty.app/Contents/MacOS:/usr/local/bin:$PATH"

APPEARANCE_MODE="$1"

if [ "$APPEARANCE_MODE" = "dark" ]; then
  KITTY_THEME="Catppuccin-Mocha"
  TMUX_BG="color236"
fi

if [ "$APPEARANCE_MODE" = "light" ]; then
  KITTY_THEME="Catppuccin-Latte"
  TMUX_BG="color253"
fi

if [ -n "$KITTY_THEME" ]; then
  kitty +kitten themes --reload-in=all "$KITTY_THEME"
fi

if [ -n "$TMUX_BG" ]; then
  # Fails if tmux isn't running, that's OK
  tmux set -g window-style "bg=$TMUX_BG" || true
fi

However, I know everyone's setup is different, and maybe I'll want to change my script at some point without having to fire up Xcode (I'm not well-versed in the Apple development ecosystem, so using Xcode is very foreign to me and I'd rather just edit a shell script from Neovim 🙂) If you've found this project, hopefully you'll appreciate this flexibility as well.

Installation

First, write up a script you'd like to execute every time the system appearance changes, and save it to ~/Documents/Appearance Watcher/handle_appearance_change.sh.

Script Tips

• The parameter passed to your script will be either light, dark, or unknown
• You'll probably need to make sure to update PATH in your script if you're calling up any executables
• You may want to run this application in debug mode in Xcode to see if it's barfing on your script

Next, build this project and install it on your machine.

1. Open it in Xcode
2. Select Product -> Build for -> Running, let it build
3. Select Product -> Archive
4. Click Distribute App
5. Select Custom and click Next
6. Select Copy and click Next
7. Save it wherever you want, click Export
8. Move the exported Appearance Watcher.app file over to your /Applications dir
9. Open the app and let it run. If all has gone well an eyeglasses icon will show up in your menu bar.

Optionally, and most likely, you'll want to set it up to start automatically

1. Navigate to macOS System Settings -> General -> Login Items & Extensions
2. In the Open at Login section, click the "+" icon to add a new application
3. Select Appearance Watcher.app and click Open