+2  A: 

What I know is the action bar icons appear next to the minimize/maximize icons if they can fit, and appear below them if not. I did not experience the phenomenon you describe, but it's common practice to have only icons in view action bars. I recommend reading the Eclipse UI Guidelines.

thSoft
Plus, the behavior may vary between platforms and Eclipse versions (e.g. on OS X, SWT Cocoa and SWT Carbon will behave differently).
zvikico
So it is essentially not possible to determine how exactly the GUI will behave? I find that hard to believe.
Mauli
And plus... even if you have only icon and the icon is too big or there are too many icons, you will see them also in new line.
nanda
@nanda That's what I said exactly. :)
thSoft