Stuart's Blog

Last month, Guru Labs taught a custom on-site class at BYU. Happily, this gave me a chance to visit former co-workers. Doing so was not only enjoyable, but also educational. While I was there, Jack Harris shared a trick with me. He'd discovered that that the Distort screensaver could be configured to display regularily updated information while keeping the monitoring system protected.

The Distort screensaver takes a picture of your current desktop then displays it slightly modified, or "distorted". Just start one of more monitorig tasks, then start the locked screensaver, and you've got a password protected, regularily updated monitoring station. The following is my opinion of how best to configure it.

Screenshots were taken using xscreensaver-demo to configure the X screensaver. On Fedora Core 3, it can be found under Applications > Preferences > Screensaver. On Ubuntu, it can be found under System > Preferences > Screensaver. Unfortunately, I couldn't find an easy way to get this same effect in KDE on SUSE.

Start by making sure that Distort is the only screensaver used. Cycling after one minute will cause Distort to refresh its picture of the desktop, thereby displaying any updates from the monitoring tasks. Locking the screen after zero minutes will make sure that the system is password protected as soon as the screensaver starts. Note, however, that this does not prevent any anyone from switching to another virtual terminal by pressing Alt+Ctrl+Fn.

Under the "Advanced" tab, make sure that the screensaver has permission to take a picture of the desktop. I recommend a one second "fade to black when blanking" to avoid an annoying flash each time Distort switches to a new picture of the desktop.

Clicking on the "Settings" button of the "Display Modes" tab opens a window that allows configuration of the Distort screensaver. Change the setting to whatever you prefer. I personally found a single small, fast moving magnification to be the least distracting.

Posted by at 7:44 PM | Permalink

I'm currently learning TeX. It is suprisingly difficult to find a good introduction to the basics of TeX. Perhaps because its creator, Donald Knuth, already wrote the definitive work: The TeXbook. His writing style is quite readable and often enjoyable.

Besides creating TeX, Knuth is also the author of The Art of Computer Programming, a series of books American Scientist ranked along side Einstein's work on relativity and Mandelbrot's work on fractals. The man doesn't seem to know how to go only half way on a project.

I think that a couple of quotes from The TeXbook, discussing how TeX handles dimensions while laying out a document, illustrate my point nicely:

TEX represents all dimensions internally as an integer multiple of the tiny units called sp. Since the wavelength of visible light is approximately 100 sp, rounding errors of a few sp make no difference to the eye…The TeXbook by Donald E. Knuth

The units have been defined here so that precise conversion to sp is efficient on a wide variety of machines. In order to achieve this, TEX's "pt" has been made slightly larger than the official printer's point, which was defined to equal exactly .013837 in by the American Typefounders Association in 1886 [cf. National Bureau of Standards Circular 570 (1956)]. In fact, one classical point is exactly .99999999 pt, so the "error" is essentially one part in 10⁸ . This is more than two orders of magnitude less than the amount by which the inch itself changed during 1959…The TeXbook by Donald E. Knuth

If that isn't hard core, I don't know what is. I think I have a new hero.

Posted by at 9:29 AM | Permalink