Jukebox (English) has an interview with the organizers of Eurockeennes, and they talk a bit about how they got The Cure booked for the show and how long they'll play:
"Again this year, there are big headliners like The Cure or Jack White. How did you manage to get them?
Kem: For The Cure , we have booked his coming to the end of the last festival. Two years ago, we had already asked the group to come for the 2011 edition. They said that there were no dates scheduled for 2011 but in 2012 a tour would be in the program. They were asked to keep our offer for the 2012 edition. It was therefore in competition with all the festivals in Europe. But the history of the festival, their first coming in 1995, which was a huge success, programming, who would play before and after them, the entrance fee, drinks ... they have decided to come to Belfort.
JP: We are especially honored by the fact that it was Robert Smith who chose to come. He announced a huge concert nearly 2:30, which is not really normal for a festival. It is expected a very strong moment that will mark this edition but also the history of Eurockéennes." (Thanks David)