Anyway to get this working in Xojo?
Seems pretty cool.
This has been discussed at length (89 posts) in https://forum.xojo.com/16453-window-transparency-vibrancy and several members have come up with solutions.
Sam Rowlands has shared precious techniques to create Yosemite style transluscency in Xdev :
https://gumroad.com/l/DXbT
Michel was faster than me… ja Sam is our Translucy-Guru 
if you plan to go to Mac App Store, you should not use any CGS call, I think.
Has anyone done it and been approved?
Sam Rowlands. His method may not be the one you link to, though.
Hmm that other thread seems to be a better direction. Didnt show up in my search because I wasnt searching for vibrancy learned something new
As Christian suggests “CGSSetWindowBackgroundBlurRadius” will not be approved, it’s a private Apple API, which they check for.
However if you like that kind of thing, Yosemite uses it a lot and Apple made public APIs for it. The xDev article I wrote will get you up and running.
I would recommend that you take some time to experiment with your usage of ‘Vibrancy’ as it can be over done, or underdone. Also depending on the primary function of your application, you may not want to use it or offer users a way to disable it.
We have an app under development right now and the testers are mixed if they like Vibrancy or not in the main interface. Some are even reporting that the app is more stable when we’re not using Vibrancy.