weird tabs behaviour - is this a bug?

[squizzz]

Hi,

Aren't these little arrows in the upper right corner, just above editor area, get active way before wxFlatNotebook runs out of space to show any more tabs (+ leftmost tab gets hidden, which is a little bit annoying) ? It happens here with just ~60% of space used by tabs.
Can anyone else confirm this?

Steps to reproduce (latest nightly):
- just close all tabs
- then (Projects tree) doubleclick on source files to open them