Personalize your keyboard layout

I adjusted my own keyboard layout and you should too. Here we will quickly see how/why to write a XKB layout file to extend ones keyboard layout.

System stuff

What is it?

That’s easy. The XKB (X keyboard extension) layout tells your system which character/symbol to print, when you press a key on your keyboard.

Why?

Most people that start going down this path and ask Which keyboard layout should I use? probably end up with one of the modern optimized layouts, like Neo (German only). The argument being, that the layout most of use like QWERTY (or QWERTZ, etc.) sucks and makes you type slower. Which is true. Those layouts were invented to be slow, in a time of typewriters, so that commonly used keys have a higher distance between each other and jam less often. Thus it shouldn’t be surprising that one can easily construct a layout which is way more efficient. I personally never felt though, that my typing speed was holding me back. I just do not write enough (or think fast enough) to require those kinds of speeds. Nevertheless I found my keyboard always to be severely underutilized. All those symbols reachable with Shift and AltGr, that I never need, could be symbol I do need.

The symbols I added that proved especially useful:

Greek letters (α, β, γ, …). I use them extensively in writing and programming. As Python is ok with most unicode symbols as variable names you can code more expressively:
```
π = np.pi
φ = np.random.randint(360)
x = μ + np.random.rand() * σ
```
which is especially useful in the kind of mathematical, research code I am writing often. (Of course, this is more for personal code, if your collaborators are not doing the same or are Greek).
Mathematical / logic notation. With ⇔, ∥, ·, ¬,∧, ∨ etc. it is quite easier to communicate math or logic with other people quickly.
Emoticons 🤷. Yes, it is 2019 and on my phone I can quickly add smileys to a message but chatting on the computer that is clearly a lacking possibility. As emoticons are Unicode standard we can add what we need 👍👍👍.
Bringing dead keys alive. Some keys in a standard keyboard layout are so-called dead keys. E.g the grave accent `. Now for me I need the grave way more commonly as a single symbol not as a accent (⇒ à), you might be the same.

Many of the symbols I use together with LaTeX macros so I can write mathematical text:

\σ_i = \÷{\exp{\φ_i}}{\Σ_j \exp{\φ_j}}

How?

We do not want to reinvent the wheel. We just want to replace symbols that we never use with symbols that could be useful. Therefore it is best to start with a pre-existing layout. For me that would be the German QWERTZ layout. You find all XKB layout definitions in /usr/share/X11/xkb/symbols.

Looking into any of those files (e.g. symbols/de) you will find blocks of the form:

default
xkb_symbols "basic" {

    include "latin(type4)"
    include "kpdl(comma)"
    include "level3(ralt_switch)"

    name[Group1]="German";

    …
};

The xkb layout definitions are hierarchical, we can include other definitions with an include statement and override only the parts that we need. The de layout is based on the type4 layout (which itself has latin as its base) in the file symbols/latin. Further included is level3(ralt_switch) which will make Alt the modifier with which the third layer is reached.

The inside of the block consists of lines like:

    key &lt;AE04&gt; { [ 4, dollar, onequarter, currency ] };

in the angle brackets we have the XKB key symbol we want to define followed by a list with the four levels: no modifier, Shift, RAlt, RAlt + Shift (for this German case).

Our own layout

We start by just importing the German basic layout (which imports all underlying imports):

default
xkb_symbols "basic" {
    include "de(basic)"

    name[Group1]="German Edited";

    …
};

If you want to have a different modifier than RAlt for level3 you have to import the definition from symbols/level3. Now we need the XKB symbol names for the keys we are interested in. For this you can run inside a terminal:

xev -event keyboard

xev is included in the x11-utils package.

xev gives you a little white window and if you press a key inside it, it will print information about the pressed key in the terminal. We are interested in the keycode. If I press my F key it will give me keycode 41. Sadly that is the keycode not the key-symbol. To find the key symbol you have to look in /usr/share/X11/xkb/keycodes/evdev. In there we find that the key symbol for key code 41 is <AC04>.

As quick rule for the rows of the keyboard: The number row is <AE##> (Key 1 ⇒ <AE01>), and the three letter rows are from top to bottom <AD##>, <AC##> and <AB##> (Key Q ⇒ <AD01>, Key A ⇒ <AC01>, Key Y/Z ⇒ <AB01> for QWRTY/Z). Inside the rows the numbers increase to the right.

Now we want to update our F key to have the Greek small and big Phi on the third and fourth layer so we write:

key &lt;AC04&gt; { [ f, F, Greek_phi, Greek_PHI] };

We write Greek_phi instead of φ. Except for the absolute basic numbers and Latin alphabet you cannot just write the symbols you want but have to use an identifier. A subset of Unicode symbols have defined names in X11. A list of those given names is in /usr/include/X11/keysymdef.h. You can use any name from this header file, ignoring the leading XK_. More realistically you can also look in other layout files from xkb/symbols. Besides the given names you may use any Unicode character. For 👍 that will give you U+1F44D which you can use in the form U1F44D inside the layout. You can also use the Unicodes instead of the given X11 names (losing some readability…).

Change all the keys you need, put them into the xkb_symbols block and save the file to somewhere, lets say deedit. Next you can install the file into the symbols directory:

sudo install -Dm644 deedit /usr/share/X11/xkb/symbols/deedit

It is probably a better idea to make a package out of your layout for which you can check your distros documentation (⇒ for Arch Linux: PKGBUILD, example).

Lastly, you change your current Keyboard layout and try it out:

setxkbmap deedit

If your happy with it and want to make it stick, append the previous line to your xinit.rc so that it is loaded on every boot.