how to get windows id of tagged "windows"

Hi!

I've wanted to do this for quite some time: I want to sent some keys
(like Page_Up/_Down) to unfocused windows and have found a program to
do it: xvkbd (X virtual keyboard) can send any keysym to any of your
windows. Naturally I'd like to integrate it with ion. My question is:
how to get the XID of a tagged window - so you can tag a window you
want to send your keys to ? 

I've read some of the documentation but could not make much use out of
it (i.e. I know it is the WRegion which is tagged - but how to get from
there to the WClientWin ?).

Thank you!


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