Create Clickable Window for Linux

I want to click through the window. The window I click, but the click goes to the window below it.

I found these two solutions for windows:

How to click through PyQt windows
I have a form that can "click on" ie. hide clicks in the window below. How can I undo changes after an event?

But I want it to work on Linux. I am looking into xlib mechanisms, but cannot figure out how the window stack works. Actually I can get all windows from XQueryTree()

and find the ones under my window. But I don't know, the witch is above.