The Custom source lets you enter a command that runs on the Mac. This is a paid feature. See What's free, what's paid. For the basics of adding a control, see Build your first deck.
Set a custom command
- On the Mac, open the menu-bar popover and choose
Edit decks…. - Add a control, or select one you already have.
- In the action picker, choose the
Customsource. - Enter the command to run on the Mac.
- Set a label and an icon, then save.
How it stays safe
When you save a custom command, Treadle gives it a generated id. The iPad only ever receives that id, never the command text. Pressing the control tells the Mac to run the action with that id. This is the same rule as every other action: the iPad sends a name, not a command. See the concepts page.
When to use a custom command
Reach for a custom command only when neither a built-in action nor a Shortcut will do. A Shortcut is often the simpler choice and is free.
If it does nothing
Check that the command runs on its own in a terminal on the Mac, that any helper tool it needs is installed, and that Treadle has the permissions the command relies on. See A button does nothing when I press it.