Trackpad workarounds: using function keys as mouse buttons (Shallow Thoughts)

Akkana's Musings on Open Source Computing and Technology, Science, and Nature.

Sun, 26 Jul 2015

Trackpad workarounds: using function keys as mouse buttons

I've had no end of trouble with my Asus 1015E's trackpad. A discussion of laptops on a mailing list -- in particular, someone's concerns that the nifty-looking Dell XPS 13, which is available preloaded with Linux, has had reviewers say that the trackpad doesn't work well -- reminded me that I'd never posted my final solution.

The Asus's trackpad has two problems. First, it's super sensitive to taps, so if any part of my hand gets anywhere near the trackpad while I'm typing, suddenly it sees a mouse click at some random point on the screen, and instead of typing into an emacs window suddenly I find I'm typing into a live IRC client. Or, worse, instead of typing my password into a password field, I'm typing it into IRC. That wouldn't have been so bad on the old style of trackpad, where I could just turn off taps altogether and use the hardware buttons; this is one of those new-style trackpads that doesn't have any actual buttons.

Second, two-finger taps don't work. Three-finger taps work just fine, but two-finger taps: well, I found when I wanted a right-click (which is what two-fingers was set up to do), I had to go TAP, TAP, TAP, TAP maybe ten or fifteen times before one of them would finally take. But by the time the menu came up, of course, I'd done another tap and that canceled the menu and I had to start over. Infuriating!

I struggled for many months with synclient's settings for tap sensitivity and right and left click emulation. I tried enabling syndaemon, which is supposed to disable clicks as long as you're typing then enable them again afterward, and spent months playing with its settings, but in order to get it to work at all, I had to set the timeout so long that there was an infuriating wait after I stopped typing before I could do anything.

I was on the verge of giving up on the Asus and going back to my Dell Latitude 2120, which had an excellent trackpad (with buttons) and the world's greatest 10" laptop keyboard. (What the Dell doesn't have is battery life, and I really hated to give up the Asus's light weight and 8-hour battery life.) As a final, desperate option, I decided to disable taps completely.

Disable taps? Then how do you do a mouse click?

I theorized, with all Linux's flexibility, there must be some way to get function keys to work like mouse buttons. And indeed there is. The easiest way seemed to be to use xmodmap (strange to find xmodmap being the simplest anything, but there you go). It turns out that a simple line like

  xmodmap -e "keysym F1 = Pointer_Button1"
is most of what you need. But to make it work, you need to enable "mouse keys":
  xkbset m

But for reasons unknown, mouse keys will expire after some set timeout unless you explicitly tell it not to. Do that like this:

  xkbset exp =m

Once that's all set up, you can disable single-finger taps with synclient:

  synclient TapButton1=0
Of course, you can disable 2-finger and 3-finger taps by setting them to 0 as well. I don't generally find them a problem (they don't work reliably, but they don't fire on their own either), so I left them enabled.

I tried it and it worked beautifully for left click. Since I was still having trouble with that two-finger tap for right click, I put that on a function key too, and added middle click while I was at it. I don't use function keys much, so devoting three function keys to mouse buttons wasn't really a problem.

In fact, it worked so well that I decided it would be handy to have an additional set of mouse keys over on the other side of the keyboard, to make it easy to do mouse clicks with either hand. So I defined F1, F2 and F3 as one set of mouse buttons, and F10, F11 and F12 as another.

And yes, this all probably sounds nutty as heck. But it really is a nice laptop aside from the trackpad from hell; and although I thought Fn-key mouse buttons would be highly inconvenient, it took surprisingly little time to get used to them.

So this is what I ended up putting in .config/openbox/autostart file. I wrap it in a test for hostname, since I like to be able to use the same configuration file on multiple machines, but I don't need this hack on any machine but the Asus.

if [ $(hostname) == iridum ]; then
  synclient TapButton1=0 TapButton2=3 TapButton3=2 HorizEdgeScroll=1

  xmodmap -e "keysym F1 = Pointer_Button1"
  xmodmap -e "keysym F2 = Pointer_Button2"
  xmodmap -e "keysym F3 = Pointer_Button3"

  xmodmap -e "keysym F10 = Pointer_Button1"
  xmodmap -e "keysym F11 = Pointer_Button2"
  xmodmap -e "keysym F12 = Pointer_Button3"

  xkbset m
  xkbset exp =m
  synclient TapButton1=1 TapButton2=3 TapButton3=2 HorizEdgeScroll=1

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[ 20:54 Jul 26, 2015    More linux | permalink to this entry | comments ]
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