New feature for game developers coming to Jaunty
Without relative mouse movements, a game like an FPS has to guess which way the mouse is moving by regularly comparing the current position of the pointer with where it used to be, periodically warping the mouse to the center of the screen. This has several drawbacks: it's a kludge to implement, mouse accelleration gets really weird, and if the cursor is moving fast enough it might escape the window or hit the edge of the screen. You hear a spy sweeping up to backstab you, race your mouse to make a quick 180, and instead stop 3 times along the way. If you're a twitch gamer, the whole experience can be more jerky than you'd find at a 7-11 counter.
We've been working around this for years in Wine, and the result has been user frustration. Fortunately, the X.org guys have heard our feature request: relative mouse moevements are being included in the XInput2 design, and XInput2 is on the feature goals list fo 7.5.
This is an example of another great thing: time-based releases. We know X.org makes releases in February, we know Gnome makes releases in March, and we know Ubuntu will release in April. When Wine or some new game needs relative mouse movements for our next release we can depend on that feature, freeze around the same time as Gnome, and quickly get a stable piece of software out to the masses. When a project like Wine releases at just the right moment, we minimize the amount of time that users are stuck with an out of date version.
If I rub the right shoulders hard enough, Wine will be making its 1.2 release around March, just in time for Jaunty. Alexandre Julliard (the project lead), expressed ambivalence about the idea during Wineconf, but I think I can convince the team with some effort. Ubuntu (and any other distro releasing at the same time, like Fedora) would benefit greatly from Wine 1.2 in the next release :)