Essentially I'm confused over when and how the options menu is shown with devices with and without menu buttons on Android devices 3.0 and above.
Focusing specifically on options menu, I know from reading that the options menu is inflated in onCreateOptionsMenu (whether via menu button or action bar) and the Google developer site states that 'items in your options menu appear on the screen depends on the version for which you've developed', i.e. bottom menu or action bar.
I've tried a few apps (e.g. gmail) on a Nexus 4 and Samsung phone, both with Jelly Bean. The Nexus has no menu button and gmail displays the options menu in an action bar. On the Samsung there is a menu button and there is no action bar, you have to press menu.
Is the options menu handled automatically by Android or is there some code going on within the app to determine if a menu button is present?
Also, what further confused me (i.e. contradicted this thought) is the Android developer site says if you use Theme.Holo you get an action bar, which kind of tells me it's not implicit how the action bar is displayed.
Thanks for any guidance.