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frugal technology, simple living and guerrilla large-appliance repair
Wed, 21 Nov 2012

Is touchpad sensitivity to blame for erratic behavior?

I'm still trying to get to the bottom of the erratic cursor movement when the Alps touchpad in my Lenovo G555 laptop is in tap-to-click mode.

Having found that this happens only rarely in GNOME, I've tried to find the differences between touchpad configuration in GNOME 3 and Xfce (version 4.8 is what I'm running in Debian Wheezy).

Running a diff on the files has produced a few differences, but nothing that affects sensitivity.

So I've been delving into the many settings of Synaptics and Alps touchpads -- all accessible through interfaces meant for Synaptics touchpads, by the way.

In most modern Linux distributions, you can control the touchpad through the synclient utility. While man synclient helps in figuring this out, you need to look at man synaptics much more closely. That's where the keys to the touchpad-controlling kindgdom really lie. They tell the truth, but that's where they are.

One thing I did was write a couple of scripts that turn tap-to-click on and off. I don't think these needed to be in /usr/local/bin, but I put them there anyway. They did need to be executable. In Xfce I made program launchers on the desktop that call both of these scripts so I could turn them off and on, using the touchpad's tap-to-click when I want and turning it off when it's annoying me.

There are usually system utilities that can help you do this, but they're usually a few menu clicks away, and Xfce in Debian Wheezy -- at least the way I have it set up -- doesn't offer to toggle this behavior for me. And the scripts with launchers are faster anyway.

I'll go into detail about all of this in the near future when I have all of the settings more set.

For now I'm experimenting with touchpad sensitivity. There are a few parameters that seem to control this, and I began by focusing on FingerHigh.

I raised the number to reduce the sensitivity of taps on the touchpad, meaning it takes a harder tap to actually register a tap.

Here is how I set it in the terminal: $ synclient FingerHigh=35

I think the default value was something like 12. When I got to 40, tapping pretty much stopped working. So I'm working with FingerHigh=35 for now.

Another parameter I've been experimenting with is PalmDetect, which is supposed to ... detect your palm.

Once I get the scripts in better shape, I will both publish them on this site and in a publically available repository.

This kind of command-line tinkering and extremely simple scripting is not at all complicated. It's the kind of hacking anybody can do.

Touchpad sensitivity is a problem I've seen not just in the Lenovo G555 but in Windows 7 as well as in Linux, and the lack of control that users in Windows have over behavior of the hardware is a terrible situation.