Hi Samoht,
Thank you for looking at that panel. If I could do it again, I would do it differently.
Those particular functions don’t use the ‘source’ parameter. It is just generated as a template when you attach a function to a modulator in Ctrlr called when the modulator value changes.
Where I do use it is in a function selector_change in the panel C-PLG-150-AN ctrlr.org/c-plg150-an although I’ve forgotten why 🙁 Something to do with changing the arguments to a class constructor there. That panel is quite complex, at least for me, so simpler panels like the ‘Roland JD-990 Bulk Dump utility’ are probably much easier to sift through!