const sf::RenderWindow& getWindow() const
{
return mWindow;
}
That function won't allow you to actually edit the window instance since it's returning a constant reference to mWindow. If you want to edit the window when you get the reference to it, then:
sf::RenderWindow& getWindow() const
{
return mWindow;
}
The const at the end of function name means you won't be able to edit mWindow within the getWindow() function, which is fine because all you're doing is "return mWindow;". There are deeper meanings to what const does but I will advise you to look up C++ Const Correctness (http://www.cprogramming.com/tutorial/const_correctness.html), if you want a better understanding of how it works.
Hope this helps.