Tuesday, July 01, 2003

Looking Outside the Screen

Why is our view of the screen on a desktop so static? Since the dawn of the metaphor, we've been looking at a fixed-size window that implicitly contains all of the space. In Unix, there are lots of various windows managers that support "multiple" desktops, so you can page around to completely different views. This would be a huge step forward from Windows, but it's still basically the same metaphor.

I think we can make other improvements without even leaving the desktop metaphor. For example, why can't we zoom? Again, there are freeware apps that can do this sort of thing (and I think MacOS comes with something like it). But I'm not just talking about a magnifying glass; I want to zoom in on documents. And, if I can zoom in, I should be able to zoom out. And if I can zoom out, then why is there an arbitrary limit to the apparant size of my screen?

However, this introduces complications. Now, when I'm looking at my screen, I'm really seeing just a subset of the available "desktop." My screen is, in fact, a window (or more accurately a viewport). However, I don't want to have to scroll back and forth, up and down, to find my apps or icons. I need a better way to visualize the entire field. In fact, this is just one instance of a larger problem. Think about the problems you have using MapBlast or other online maps: either you're zoomed out and can see the points of interest but not the street you're on, or you're zoomed in enough to navigate locally but have lost sight of landmarks.

Researchers at (surprise) PARC have come up with one very cool way to indicate nearby but offscreen destinations. A system called Halo draws a circle around the destination, with a radius sized exactly so it just barely intersects your visual field. You can tell the direction of the destination by judging the center of the circle, and you can judge the distance by the shallowness of the arc. A very shallow arc means a large radius and thus the destination is far away; a sharper curve means a smaller radius and a closer destination. It's very non-intrusive because by design, the arcs only overlap a few pixels on the edge of the screen (see http://citeseer.nj.nec.com/561859.html).

As more and more of what we do is through smaller keyholes into larger fields, we need more elegant tricks like this to help us find our way.