Setting to let mouse events pass through GUI application

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http://askubuntu.com – I am using compiz to make an app transparent. I would like to be able to click through the app as well. Q: There are any settings in the GUI (Compiz) or via CLI to be able to set up an application (based on it's class like in Compiz) to not capture mouse events and just pass through it, or even better to enable capturing the mouse when a key combination is pressed (ex: left ALT + left Ctrl + mouse click) ? Use case: I am watching a conference online (let's say Google I/O), I am setting the opacity of the video app via Compiz (CCSM) to be very transparent, and only increase it's opacity when (HowTos)