Copy Attributes copy visual transformation (e.g. location/rotation) problem with Child Of constraint
Open, Needs TriagePublic

Description

Blender Version
Broken: 2.79

Short description of error
I'm trying to use the "Copy Visual Location" and "Copy Visual Rotation" functions from the Copy Attributes addon to get around a problem in rigging a character.
(BlenderArtists post: https://blenderartists.org/forum/showthread.php?440992-IK-FK-setup-Bone-position-changes-when-dialing-between-Child-Of-constraints)

Normally, copying visual transformation works perfectly fine. But when the bone having the visual transformation applied to has a Child Of constraint, the result is always offset. Demo:

Example file attached.

Details

Type
Bug

You just have to press Set Inverse button of Constraint to obtain desired result.

Thanks for the quick reply, @ronan ducluzeau (zeauro).

While what you suggest is true, this is actually a part of a bigger system that will be animated where I can't be clicking on the "Set Inverse" button whenever (Refer to the BlenderArtist post: https://blenderartists.org/forum/showthread.php?440992-IK-FK-setup-Bone-position-changes-when-dialing-between-Child-Of-constraints)

Unless there's a way to keyframe "Set Inverse"..?

I re-read your thread on Blenderartist. And I don't think this case was anticipated when constraint was made.
The idea was to use influence slider as a posing tool and only insert visual keyframe to finally don't use constraint at all while playing the animation.
So from this perspective, it looks like a bad idea to add a driver to a second Child of constraint.

I am not so experienced in animation and rigging.
So, it would be better to wait from @Joshua Leung (aligorith) 's opinion.

Thanks, @ronan ducluzeau (zeauro), I appreciate the feedback.

Ultimately, my problem is what's in the forum thread, but one solution to it is if I could get what I reported here resolved.

If @Joshua Leung (aligorith) has a way to resolve this, or could suggest how to tackle the original problem, that'd be awesome.