If your mouse is moving an enchanted item, the debug pie will have a weird purple box around it. It goes away if you have a potion effect, however.
Steps to reproduce
- Open debug pie (Shift+F3)
- Open your creative inventory.
- Click on an enchanted book to move it around. (Don't click it into another inventory slot, though.) --> Notice the purple box around the debug pie.
Discovered while testing and related to