Wandering Thoughts archives


Dealing with Fitts' Law on widescreen displays

One of the usual sayings derived from Fitts' Law is that four of the five easiest locations to reach with the mouse are the four corners of the screen, because they require very little precision (the edges trap the mouse and guide it into the corner). Over the years I've made some modifications to my desktop environment to make better use of this principle. The most important one is how I use the top left corner; I have my taskbar equivalent arranged so that when an iconified terminal window gets output, I can just zoom my mouse to that corner and click in order to reveal the terminal window.

Zooming to a corner is a fast operation in most setups; it works fine on a single monitor, even a single widescreen monitor, and on a normal dual-monitor setup such as my work desktop. But recently (for reasons beyond the scope of this blog) my work setup got updated to dual widescreen monitors, which revealed two problems with my application of Fitts' Law in this environment.

The first problem is that the sheer number of side to side pixels in a pair of 1920x1200 LCD panels seems to be a bit too many to easily zoom a mouse across. My mouse pointer generally winds up in the middle of the right hand display; getting it to the top left corner of the left display was no longer anything like a little flick of the wrist. The second problem is that the top left corner was sufficiently physically far off to the side that it was no longer an easy casual action to glance at it to see if there was anything with new output that I needed to deiconify; I was less glancing off a bit and more peering off into the distance.

(I had my old dual displays relatively flat against each other, but I think that I probably need to move the new displays into a much more pronounced V shape.)

My current solution to this issue exploits Fitts' Law once again. The often-overlooked fifth easy to reach location is 'where the mouse is right now', or failing that 'some large area very near where the mouse is'. So I've created a new mouse button binding for my window manager; if the mouse is over the root window, hitting the left button with Shift+Control now de-iconifies the (alphabetically) first terminal window. My mouse is frequently parked over the root window and when it's not there's generally an exposed patch of the root window close to it.

(Technically the binding toggles the window's iconified state, which means that I can flip the first window back and forth from iconified to not. This is a great way to fidget.)

To deal with the 'too far to look' issue and to make things in my terminal windows taskbar easier to reach in general, I've repositioned it so that it's at the top left corner of my second (right) display; this puts it more or less in the center of my overall workspace and makes it easier to both reach and look at. I don't think this move away from a screen corner is a loss for Fitts' Law because everything except the first window already had to be targeted carefully.

Of course, now I just have to train myself out of a many years habit of reflexively looking and going to the top left of the left display. This shouldn't take too long, right?

(What I'd really like to do is duplicate my taskbar equivalent in the top left of both displays. Unfortunately this isn't possible right now with my window manager.)

PS: I experimented briefly with increasing the mouse acceleration (which would make everything effectively closer) but didn't like the effects it had on my ability to target things with the mouse in general; I kept overshooting and missing stuff. Possibly I would have acclimatized with time and I just gave up too soon.

sysadmin/WidescreensAndFittsLaw written at 21:13:37; Add Comment

Thinking about spam rejection and abuse addresses

Somewhat recently we got a spate of spam messages to our abuse address, which set me to thinking about the mostly theoretical issue of how to treat email to it.

(It's a mostly theoretical issue for us because the volume of spam and other email to our abuse address is very low in general, so we're not at all likely to change anything about it.)

On the one hand, visible spam rejection of email to abuse addresses is one of the things that really gets on people's nerves; it's famous for rejecting real spam complaints because, of course, they contain spam. Your spam, that people are trying to complain about.

On the other hand, email to abuse is going to go through our spam scoring system and get tagged if the system thinks it's spam. Pretty much everyone here either discards spam-tagged email outright or filters it to a separate folder. My mail filtering deliberately excludes email to abuse (among a few other things), but I don't know if anyone else either bothered or even thought of it; it's not necessarily something that comes to mind when you're setting up personal email filtering.

And finally, I can't think of any actual real email to our abuse address that we've gotten in the last five years or so (since I moved to here). It's all been spam. So as a practical matter, any filtering or rejection that we do on abuse email is unlikely to affect real complaints, because we don't get real complaints (hopefully because our users and machines don't generate spam, as opposed to people just not complaining about it).

(The other aspect of email to our abuse address is that I suspect most people are going to complaint to the central university-wide abuse address instead of abuse at our specific subdomain. The central people will then get in touch with us through our internal contact address, not our abuse address.)

This is of course a specific instance of the general spam rejection versus spam filtering dilemma. If you reject email people at least know; if you filter, there's at least a theoretical chance that you'll recover from filtering mistakes. The stakes are higher for the abuse address because it is one of the addresses that has a very high chance of false positives (non-spam classified as spam).

The most pragmatic thing to do in a situation like this is to apply spam-filtering to your abuse address. This blackholes real spam to keep it from bothering people while carefully not saying anything to real senders who had their messages misclassified. But this pragmatism sort of bothers me because it's lying to real senders just to pacify them (their email is being ignored either way but you're deliberately doing it silently so they don't know). It would be more honest to use spam rejection on the abuse address, and it might do some good to reduce the level of spam. If legitimate email to your abuse address really is vanishingly rare, it also shouldn't affect very many people.

So what's the right answer? I have no idea.

(My current approach of exempting the abuse address from my personal filtering would not be viable if it got a lot of spam. At that point I would probably remove the exemption and let spam-tagged email to the abuse address get quietly filtered away, mostly because it's easier than trying to persuade everyone that maybe we should do spam rejection for email to abuse.)

spam/AbuseRejection written at 02:24:38; Add Comment

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