s2arrows

Interception plugin for mapping s+hjkl keys to arrow keys.

What is it?

This is a plugin to migrate the second most useful feature of Karabiner for MacOSX to Linux. With this plugin enabled, s acts as a modifier key. While s is pressed, the h j k l keys act as arrow keys, following the VI key bindings.

It also makes the s + f combination as a different modifier that maps the h, j, k and l keys to Home, Page Down, Page Up and End respectively. This is very convenient for laptops since you will not be needing the fn combination anymore. And in general, it means your right hand will have to move even less often.

Why?

It's so nice in VIM that you don't have to lift your right hand to move to the arrow keys. It would be great if you could do the same in all applications. In fact, once you get used to this, it's very hard to go back.

Dependencies

• Interception Tools

Building

git clone [email protected]:kbairak/s2arrows
cd s2arrows
mkdir build
cd build
cmake ..
make
sudo make install

Enabling

udevmon

s2arrows is an Interception Tools plugin. A suggested udevmon job configuration (/etc/udevmon.yaml) is:

- JOB: "intercept -g $DEVNODE | s2arrows | uinput -d $DEVNODE"
  DEVICE:
    EVENTS:
      EV_KEY: [KEY_S, KEY_H, KEY_J, KEY_K, KEY_K, KEY_LEFT, KEY_DOWN,
               KEY_UP, KEY_RIGHT]

If you already have an Interception Tools plugin running, like, I don't know, caps2esc, you should pipe the two commands to each other and append the keys to the list instead:

- JOB: "intercept -g $DEVNODE | caps2esc | s2arrows | uinput -d $DEVNODE"
  DEVICE:
    EVENTS:
      EV_KEY: [KEY_CAPSLOCK, KEY_ESC, KEY_S, KEY_H, KEY_J, KEY_K, KEY_K,
               KEY_LEFT, KEY_DOWN, KEY_UP, KEY_RIGHT]

systemd

A suggested systemd service to run udevmon can be setup by creating the following file (/etc/systemd/udevmon.service):

[Unit]
Description=udevmon
After=systemd-user-sessions.service

[Service]
ExecStart=/usr/bin/nice -n -20 usr/local/bin/udevmon -c /etc/udevmon.yaml

[Install]
WantedBy=multi-user.target

Then, you can enable and start the service like any other:

sudo systemctl enable udevmon.service
sudo systemctl start udevmon.service

Caveats

The main problem with using this plugin is that the s key might be interpreted as a modifier, when in fact you actually want to press s. This can happen when you type something like ssh some_host very fast. The sh part from the sentence might be interpreted as a press of the left arrow key and the end result may appear as some_hosts. The same problem used to happen with Karabiner too. Over time, you will get used to letting an extra millisecond pass after every s key press.

Another caveat is that with this plugin enabled, you lose the ability to hold the s key down and have the character repeat itself. From my experience, this has never been a problem for me.

License