Thanks to Jeff Atwood at Coding Horror I recently discovered the good old Fitt’s law. To make a long story short, it says that the larger the component is, the easier it is to click on it. The area near to screen edges is the most valuable, because from mouse cursor’s point of view it is infinite. See Particletree for a great visualization of this concept.

I knew that intuitively. It seems that UI creators have taken it into account for years, putting tiny title and task bars on top or bottom and all the most important icons in corners. I haven’t realized how important it is until I started using a mediocre dual head configuration. After all, computer is a part of me and I don’t see it until something goes wrong.

Consider this setup:

The larger display is a desktop monitor with higher screen resolution. The smaller one is my laptop. Since I am right-handed and I use laptop keyboard, it needs to be on the left. Apparently in Ubuntu the “left” monitor is always the one that gets the desktop, with task bar, shortcuts and so on. I don’t know how other operating systems deal with it, but in Ubuntu you always need to have a rectangular desktop. It means your mouse can move to the brown area, right above what you see as the top edge of the screen.

Now using a quick launch or tray on the smaller screen is quite an ordeal. Even if the displays were of the same size, or the OS dealt with it without the “brown area”, you still would have issues with window title bar icons or scrollbars.

With Fitt’s law at least I am able to name this issue.