Screen savers have been around for a long time. The original function of screen savers was to reduce burn-in of the phosphors on Cathode Ray Tube (CRT) screens by providing text or images that moved around on the screen.
Burn-in is caused when a CRT displays the same text in the same locations hour after hour for months and years at a time. This causes the rare-earth phosphors to degrade and become less luminous which can make it difficult to read the display. You can see this if you look at an old display in a supermarket or government offices in particular, where the computers and displays that are there are older than dirt.
Figure 30: Screen Savers can generate hours of mindless entertainment, and have little to do with “saving” anything these days.
Screen savers have evolved into a complex form of visual entertainment that can take not only a significant amount of CPU time to animate but also an inordinate amount of your time to choose and configure. The Screen Saver page of the Control Center allows you to select a screen saver and configure it if there are configurable options.
My personal choice is usually the blank screen, because it saves energy. The calculations required to generate the screen saver images and the energy required to display them on the screen take some energy. But I sometimes use other screen savers as the mood strikes me. They can be fun.
You can use a non-blank screen saver, but still save some energy. Use a static background image rather than a moving one which would take CPU cycles to calculate the image.
New screen savers can be downloaded directly from the KDE website at www.kde.org.
Screen savers can be used to enhance the security of your computer. When you use the Lock icon (Chapter 1) to lock your computer, whatever screen saver you have chosen is activated. However, if you step away from your desk without locking the desktop, KDE can automatically start the screen saver and lock your desktop after a specified period of time. In fact, most places I have worked have a policy that the screen saver must start and lock your desktop automatically after a specified period; usually ten to twenty minutes.
You can configure these options in the Settings box at the bottom of the Screen Saver page of the Control Center. Click on the Start Automatically check box and set the desired — or mandated — delay time and then click on the Require Password to Stop box and set the delay time for that.
Say you set twenty minutes for the screen saver to start automatically, and sixty seconds for the screen saver to lock the desktop. After twenty minutes of mouse and keyboard inactivity the screen saver will start. After another sixty seconds of inactivity the desktop will lock. You can still use the mouse or keyboard to turn off the screen saver and return to your active desktop for that last sixty seconds.
You can use these two settings in an office environment where you may get called away from your desk and where there is a corporate policy pertaining to locking up your computer when you are away from your desk. Many companies require employees to lock up their computers when they are way from their desks. The usual policy is that the screen saver should be set to lock the desktop after twenty minutes.
This feature can also be useful if you have children and want to remove their ability to play while you are away from the computer. Trust me, I have experienced the loss of documents to inquisitive little fingers.