Comment 2 for bug 1272929

@alan, I've added the `viewbox` parameter to the Nominatim call, which gives preferences to results inside the current map view. But if there is no result inside the bbox, results outside are retrieved.
The tricky part is that there are some ponderations involved in Nominatim scoring results, so it may appear that a result outside the bbox appears as more relevent than another one inside, maybe because it's a bigger city, or the name is the exact search string, etc.

Can you take two minutes and test on trunk and tell me how you feel it?

The fact is that I'm afraid that I've not many options to make this better since we rely on Nominatim.