I have just installed SFML 2.1, and it did not work.
I tried the most minimalist example, just displaying a window, and the same bug appeared. But after a few tests and after playing with displaying the size on a Event::Resized, I think I know where it comes from and SFML is probably not the problem !
I am using Gnome 3 as Desktop Manager, and I have been toying with extensions. One of them removes the black top bar and lets it reappear when the cursor goes on top. After disabling it, it became clear : the top bar is approximately 30px as well as title bars of windows. So it is about 60 extra pixels. Given that I want a drawable window height of 720 and that I have at most 768 due to my resolution, I only get 708 of drawable height. I suppose SFML, in this case, decides to resize the window in order to fit the available height (and not keeping the ratio, but this is not the problem) and the available width as well.
So maybe the tweak that I am using to remove the top bar is not a) well implemented b) not supported by SFML, so that SFML "thinks" that only 708 pixels are available and decides to resize.
The last thing I do not understand is why then when it takes the decision to resize, the height occupies the whole height - that is the space normally taken by top bar. It is like it thinks that the top bar is there, so decides to resize, and at the resize no longer thinks the top bar is displayed...
But now that I understood what was going wrong, I'll try to figure a software solution out
