Location Bar like Widget

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Hi

For my application, I need a GTK Widget not unlike the location bars in mozilla,
nautilus, ...

More specifically, it should allow to:
* change its list of items dynamically while the combo is expanded.
* send events for keystrokes,clicks and mouseover/out for items, so i can
highlight them.
* display an optional icon in front of every item
* have parts of the item text in bold and other parts in italics

I think I will have to write the widget myself. So my questions:

Does a similar thing already exists somewhere so that I can use
it as a starting point ?

If not, I will use the standart GTK combo as starting point. How can I change
its item list while its expanded?

Thanks,
Thomas