Topic: How did they make this reactor work? - Reverse Engineering

[gumbtg]

Please watch the attached Gif
Does anyone have any idea how they made the following behavior?

Context:
Entity is a block of a custom type
When you grab the grip of block, it stretches another line within the block
The block has not dynamic parameters. Only attributes.
This behavior was created by a 3rd part plug-in known as DesignMaster

What's interesting is that within Block Editor there are no grip or strecth parameters. Only Attributes. Which tells me they are possibly adding a reactor to the block? Do you agree? I dont even know how you have all these grips for a block without point parameters.

When I investigate the reactors within the dwg, I do find one that I believe to be the owner of the block in question.

Just kinda curious if anyone has any idea how one would design this functionality. Im impressed. Thanks!
I have attached the drawing below
I have attached the lisp routine I used to investigate the reactors within the drawing and for the block

[Lee Mac]

The object in question is not a block reference, but rather a custom entity created using ObjectARX (which is rendered as a proxy object when viewed in an application in which the add-on in question is not installed); as such, this is far beyond the realms of the LISP API (though, it could be loosely imitated in LISP through the use of VL Reactors).