Question: mac layout change watcher

[alex-enchi]

Hi all

Do you know is there a good method to be notified on layout change on macos, aside of checking with interval for
defaults read ~/Library/Preferences/com.apple.HIToolbox.plist AppleSelectedInputSources

Ideally I want to set specific layer on when changing layout and interval does not sound like a best option

Best

[fdidron]

I'm not super familiar with macOS, but I think this will require some Swift / ObjectiveC code to subscribe to system's notifications.

Wouldn't it be easier to have a script (Apple script or any automation tool) that you invoke with a key shortcut that:

1. Sets or cycles the input method
2. Read the value of AppleSelectedInputSources
3. Sets the layout accordingly to the value with kontroll

[alex-enchi]

I thought about it as well, but it means that layout must be changed only through shortcut.
Recently I tried option with listening for file changes of that plist file, but apparently file is not updated right away.

[jcrawford]

@alex-enchi You can use AppleScript but you would have to use polling to determine if the value has changed. You could use the on change handler but this would only be fired when the value is changed by the user and not when the system changes the value.

A simple polling script would look something similar to this.

on run
  tell application "System Events"
    set previousInputSource to (get AppleSelectedInputSources)
  end tell

  -- Loop to continuously check for changes
  repeat
    tell application "System Events"
      set currentInputSource to (get AppleSelectedInputSources)
    end tell

    if currentInputSource is not equal to previousInputSource then
      -- Execute the shell script to interact with the keyboard
      do shell script "/path/to/your/update-layout.sh"
      
      -- Save the new source for future use
      set previousInputSource to currentInputSource
    end if

    delay 1  -- Check every second (adjust as needed)
  end repeat
end run

If your bash script is simply executing a kontroll command you could do all of the work in the apple script itself and not have to call the bash script. do shell script "kontroll set-layer --layer <INDEX>"

When it comes to making your applescript run continuously in the background launchd is your friend, you can see how it is done here: https://apple.stackexchange.com/q/192600