If you were bothered by a missing command or key in the terminal-app keyboard, rest at ease - we've got you covered. This time you will see how it is possible to easily define custom JavaScript Object Notation / JSON lightweight data-interchange format layouts. We would like to thank Filippo Scognamiglio [1] for the tutorial bellow.

In this post we are going to walk you through the construction of a simple VIM profile. 

For starters we create the custom layouts directory:

mkdir ~/.config/com.ubuntu.terminal/Layouts/

All the JSON files inside it will be parsed when the application starts, so let’s create an empty file with your favorite editor (we are guessing it might be vim at this point).

vim ~/.config/com.ubuntu.terminal/Layouts/vim.json

The root object contains some pretty basic items like the name, the short_name which is shown on the selector, and the language (which will be used in the future).

All of the actual controls will be stored in the “buttons” array. Every button object is comprised of a main_action (triggered by click) and an other_actions (triggered by click and drag in a sub-menu). There are currently two types of actions: a “key” action which simulates a keystroke (with optional modifiers), and a “string” action which sends a whole string to the terminal. Each action will also have a text property, which is shown to the user.

Let’s start by emulating a very useful vim control: Escape. There won’t be any additional actions; the type will be “key” and we have arbitrarily decided to display “ESC” to the user. Our final button will be as follows:

The list of keys that can be used is taken from here: http://doc.qt.io/qt-5/qt.html#Key-enum . Please remember to only use the name after the prefix “Key_”, so the name “Qt::Key_Escape” becomes just “Escape”. Modifiers can be specified with the “mod” attribute, and the valid values are: Control, Alt and Shift.

Now let’s move on to the close and save commands. In vim we generally type the strings “:q”, “:q!”, “:wq” to close the file dropping or storing the changes. Since the correlation is strong we decided to put them in the same semantic button with “:q” as the main action and the other two as secondary actions. This time we want to send a string instead of a single keystroke so type will be set to “string”.

The complete sample vim profile can be found here: https://drive.google.com/file/d/0B2KuANIptmZhWlQzdnVGLV9CZ00/view?usp=sharing .

That’s it. If your custom profile doesn’t load, then you probably have a syntactical or semantic error in your json file. Check the standard output to see what’s wrong.

We strongly encourage you to play with this feature and share your achievements with us, and we are always eager to see new profiles or patches to the default ones.