By John Deurbrouck Screen savers were invented to prevent unchanging images from burning into the phosphors on your monitor's screen. While newer monitors are not prone to that kind of damage, the screen saver with a password feature has turned out to be a handy way to secure your machine while you're away from it. The problem is getting the screen saver to kick in at the appropriate time. If you're working on sensitive material, you may not want to leave it visible to all passersby while you're away. But any time out short enough to be serviceable for security is hard to live with while you're working.
Some screen savers offer another control mechanism.
Pack, you can designate corners of the screen as hot and cold corners. When you put the mouse into the hot corner, the screen saver is invoked immediately. When you put the mouse into the cold corner, the screen saver is prevented from starting up. These mechanisms do work, but they're easy to invoke accidentally. SCInvoke presents a tiny dialog box that's almost entirely covered by a single button.