You should be able to select an item in a combobox by typing it's name. This is
consistent with how comboboxes in webpages in most webbrowsers work.

Of course, I expect more and better from GNOME/Gtk+ folks, so I'd say the best
behavior would be that typing opens up the menu and then actively searches
inside of it. That way the user gets to see what's in the combobox as they type it.

I think it would be most usable if typing immediately started selecting, so that
the flow for a user went:
1.Tab (or Alt-mnemonic) to select the combo
2. types what they want to select
3. hit space or return to select it

However, if we're worried that typing changing the selection would be
confusing/surprising, then perhaps the typing would be available after opening
the combo, so that the flow became:

1. Tab or Alt-Mnemonic to select box.
2. Hit space to open menu
3. Type to select item
4. Hit space or return to select an item.

Note that I'd also consider the current solution for browsers an improvement on
the current behavior. This case goes as follows:
1. Tab to select combobox control
2. Type and watch the value change magically.
Of course this last case is a bit mysterious/confusing -- I think we can do better!


Other information:
Apologies if this is a dupe or if this has been discussed elsewhere -- I can't
imagine it hasn't come up, yet this has bothered me for ages and I couldn't find
a bug report for it. Also, I'd be happy to try to help implement this with some
hand-holding if there's an IRC channel I should hop on or something to get help
starting.