be informed when Mouse Dragging Frame

Question

When a mouse drags a maximized frame, that frame will become a normal size (i.e., not maximized).
It seems that Emacs will receive a message when its frame is being dragged by a mouse.

I want to run a set of functions when a mouse starts dragging (mouse starts moving after its left button is down) the frame
and another set of functions when the mouse-1 button is released after dragging.

Is there any relevant hook?
If not, how to implement that?

---

Here's a similar thing: 16.1 How Programs Do Loading:

Variable: load-in-progress
This variable is non-nil if Emacs is in the process of loading a file, and it is nil otherwise.

Answer 1

Is there any relevant hook?

Yes, it is move-frame-functions.

Functions run after a frame was moved.