White bars on either side of text in fullscreen?

I’m not sure if this is a bug or a feature that I have yet to figure out. I’ve done some searching and haven’t found anything about it, but apologies if I missed a thread.

I am running Scrivener v 3.2.1 on MAC OS X v 10.7.4 (not Mountain Lion).

I have the editor text background blue-ish and the editor page background brown-ish. Everything works fine in windowed mode. But when I enter fullscreen (NOT compose, I mean Apple’s fullscreen mode), if I wrap the text I see blue pages and a brown background. But if I leave the editor ‘unwrapped’ I see the text over a blue background in the middle and white bars on either side.

What’s going on here? (I can post sceen shots if need be.)

Thanks!

You can turn this off by deselecting “Fixed width” in the Editor pane of the preferences - it’s to prevent super-wide text on large screens.
All the best,
Keith

Thanks!