Detecting interface open

[Edda]

Hello there.

How to detect if 'any' of the interface layer is popped open ? I.e. inventory or team window or any other window including the 'esc' menu. Do I have to check for every one of it ? And which event(s) is that related to ?

I would like to fire an event if any UI window is open to hide my AddOn.

And by the way, is there a function to hide/show a control 'smoothly' - that is to have it fade to transparent or pop visible elegantly like you could do in JQuery ? Is this integrated or requires to code a function for that ?

A nice day to you - thanks for any feedback.

*edit* I forgot to ask : I want to detect if the player sheathed/unsheathed his/her weapon (~combat mode) to hide/unhide my UI. I checked the doc but didn't find anything so far.