Writing alternative File Widget Okay, so I looked inside of the Managed File element and the FileWidget code and I am pretty overwhelmed.  I don't think I need anything quite so complex, but it seems like there is so much that can be done with a file widget that I don't want to do things in a way that could cause problems in the future.

I have some javascript that will upload a file to a remote server and return a url, so I want to send that url to a custom controller and save it in Drupal.  Is writing a file widget the right way to go here?

Any guidelines on where to go to find a good example of a file widget, or an explanation of how it works?
I've found that at the moment, there is no example more helpful than the Plupload module.  It integrates with the Plupload_widget module and extends the FileWidget from core and also has a lot of comments that I wish core would have included, explaining what the core file widget does.