On IRC DevilWithin just pointed out a bug in SFML with the Windows implementation.
If you're checking for the MouseMoved event and then press the ALT key, the MouseMoved event will not get triggered anymore until you either press any alpha-numberic, the ALT or the ESC key or you click somewhere.
The bug probably occurs because the ALT key normally gets directed to the menu which doesn't exist in SFML. Visually you can't see a difference but from the message queuing the Window somehow loses the 'focus'.
Here's a minimal complete example that will reproduce the problem:
#include <iostream>
#include <SFML/Graphics.hpp>
int main()
{
sf::RenderWindow window(sf::VideoMode(800, 600), "MouseMoved Bug");
while(window.isOpen())
{
sf::Event event;
while(window.pollEvent(event))
{
if(event.type == sf::Event::MouseMoved)
std::cout << event.mouseMove.x << "," << event.mouseMove.y << std::endl;
}
window.clear();
window.display();
}
}
On the console you'll see the mouse position received via the event. Now as soon as you press ALT the event won't get triggered and there will be no fruther updates on the console.
I'm not quite sure if this is really related or if the bug is triggered through something completly diffrent, but here's a link (http://stackoverflow.com/questions/9627379/how-to-disable-normal-behaviour-of-alt-key) to a code example that shows how to disable the ALT key interaction with window menu.