Having numerous windows opened in the same time on the desktop, makes giving focus an action to be considered for optimizations.
Ubuntu offers, by default, the traditional way of dealing with windows by letting the user to give focus to a window by clicking on it, meaning, users can easily bring a window in an active/focused state via just 1-click.
There are users who prefer the focus-follow-mouse approach (the reasons can vary from speed, simplicity, consistency with other OSs' methods, etc), meaning a window becomes focused by just hovering the mouse pointer over it, thus eliminating the need to click on it.
The focus-follows-mouse can be easily enabled via Unsettings, a light utility that deals with numerous Unity configuration options:
- first, install Unsettings (Oneiric, Precise)
sudo add-apt-repository ppa:diesch/testing
sudo apt-get update
sudo apt-get install unsettings
- then, navigate to
Unsettings-->Windows-->uncheck Click to focus-->Apply settings
The above behavior is usable on both Unity and Unity 2D but applied per-session (applied under Unity, applied under Unity 2D from the same interface).