I've been trying to create custom gizmos for a Python addon, which in the very long term will be quite important for future productions (one of the most highly requested features from my animators for the past 15 months has been better bone widgets).

While doing that though, I've run into a lot of missing or confusing descriptions for properties and functions for Gizmos and GizmoGroups. In this patch I've tried my best to fill out what I could, but I can't say I was very successful. There are a lot of things that would be a pretty significant time investment to figure out on my own, so I would love to get some help.

CC @Campbell Barton (campbellbarton) @Sebastian Parborg (zeddb)

Future:

• I don't know if a general technical overview of the custom gizmos design exists, but I think it would be really good to have.
• More python templates could be added, eg. for taking data from a real object and using that to draw it as a gizmo. I could do this.
• If we run into bugs while figuring these things out, it would be good if someone could take some time to clean those up as well.