Version:            (using KDE 4.0.1)
OS:                Linux

In many applications, focus highlighting is instantaneous - that is, if the mouse moves over an icon, it becomes highlighted. If I am moving my mouse across a field of icons from icon A to icon B, this results in all the intervening icons being highlighted very briefly, producing the illusion of flickering. This is ugly. A possible improvement might be to make this focus-highlighting behavior velocity-based. That is, if the mouse is really flying over an icon, I probably DON'T want to focus on it. Only when the mouse comes to rest do I really want to focus. I'm not sure how easy it is to determine the instantaneous velocity of the pointer, but assuming it's trivial, I can think of two reasonably good ways to reduce flickering: (1) fade in highlights based on velocity, so that icons between A and B would only be partially highlighted before they are de-highlighted. This seems needlessly CPU intensive. Or (2) focus highlighting moves only when the mouse is below some velocity threshold (as determined by some simple user testing). That way, if I am moving the mouse smoothly at low velocity, the highglighting will also move smoothly, whereas if I jerk the mouse from icon A to icon B, it will jump without causing flickering in the intervening icons.