There is a regression in this release:
When I switch my application to fullscreen the contents of the window do not keep their aspect ratio. They are scaled to fill the whole screen.
My system: iMac early 2009, OS X v10.11.6
Affected application is Previous: https://sourceforge.net/projects/previous/
This problem already existed in earlier version but IIRC it was fixed in 2.0.18.