[Interest] "legacy" fullscreen behaviour on Mac?

[René J.V. Bertin]

Hello,

This has been bugging me for a while: is there a way to alter the full screen behaviour of Qt5 applications on multi-head Mac systems? I have a 2-screen set-up which is configured to span each space over both screens. For me that's the only sensible way to combine multiple physical screens with multiple virtual desktops ("spaces") but it has a very annoying effect on the native fullscreen mode. 
Fullscreen mode resizes an application to take up the whole screen it is on, but blacks out all other screens.

Qt4 applications don't do this.

How complicated would it be to reintroduce the "legacy" behaviour where other screens remain usable?

Thanks,

R.