So, while I was testing following your guidelines I had issues recreating my frame drop. Then I realized that I was comparing the compiled SFML 2.3 to the pre-compiled package of ubuntu Trusty which is... 2.1.
I tested with the source code of the 2.1 and then the issue is back (but not in 2.2) so it's an issue that has already been solved...
As for the warning, that is what happens when events go unhandled. I think it should be obvious why you are seeing it after your modifications.
Yes sure, it's obvious ^^ I was just trying to know if there was other part of the system that are relaying on what happens in the code that prints the warning because I had trouble understanding it
. But I guess that it's just a warning and I can ignore it if there is no other issue with inputs.
So in the end... I think I just found an already known bug
, nothing new there and I'll now go with building the 2.3 myself instead of using the 2.1 package of Ubuntu