Question about a menubutton with a default action

Hi there!

I need some advice here... You know in Firefox, we have these doorhangers
that pop up when, for example, a site asks you if you want to save a
password. The button to save the password is actually a menu button with a
default action, and a downward pointing arrow to open a menu of more
options. That menu doesn't currently contain the default action. So the
mouse interaction is: Click on the left side, e. g. the button label,
performs the default action of saving the password. Clicking on the downard
pointing arrow will open the popup menu.

The current keyboard interaction is buggy at best. The access key doesn't
work correctly, and the button has two tab stops, one for the menu button
piece, one for the default action.

Now, I've read up on the default expected behavior for menubuttons
<http://www.w3.org/TR/wai-aria-practices/#menubutton>, but these don't
cover the case of a menu button that also has a default action. Nor is
there a different role available in IA2 or other platform APIs that I know
of that would cover this scenario in a way that the end user immediately
knows what's going on.

My first reaction to the question of how this interaction should be, was
this:


   1. Pressing the access key should focus the menubutton, but not activate
   anything.
   2. Space should activate the default action.
   3. Down Arrow should open the menu.

The problem here is that current best practices suggest that both space and
down arrow pop up the menu. And there is no good way to actually tell the
user that space would, in this case, do the default action and set focus
back on the page afterwards.

Any ideas or suggestion on how to best solve this would be appreciated. We
could do an ARIA description for this particular button that tells the
users on focus that space will submit the default action, and down arrow
opens the menu for more options. But the best way would be if we had a best
practices guide somewhere that would include this special scenario, or
settle on a good way forward for these in general.

Welcoming your comments!

Marco