Type-ahead filtering in drill-down menus

[humdinger]

It'd be nice to have the "type-ahead/filter-ahead" feature of Tracker windows in Tracker's context-menu-drill-down-navigation. I'm not sure the "type-ahead" is too nice in this context, as it'd involve jumping the user's mouse pointer; never a good idea. Instead of re-using the "type-ahead/filter-ahead" Tracker setting, it may be more prudent to just always do "filter-ahead".
As with filtering in Tracker windows, it'd be nice to use some kind of indicator that the contents is filtered. I'd say a slightly tinted background.