Inspired by Mitchell Charity’s printable paper rulers and Steve Pomeroy’s CSS ruler, I wrote a little python script to generate an on-screen ruler for the OLPC XO-1. The XO-1 screens are super high resolution (200dpi) and are each identical. This makes for a very accurate ruler. It’s one of a few project I’ve done or am working on that tries to take advantage of the physical qualities (and physical consistencies) of the XOs. Also, a ruler is just a really useful thing for a school child — or anyone else for that matter.
Of course, different screens have different pixel sizes so the ruler for the XO won’t work on another screen. This made some of my friends jealous. To appease them, I spent a couple hours and hacked up a little web frontend to my ruler generator which allows anyone to create custom on-screen rulers and to save them and share them with others who might have the same screen. I’ve called it YouRule. Please check it out or download the source and send me improvements.