i3-gaps is a fork of the i3 window manager that is kept up to date with upstream i3, and adds the feature of allowing you to have visible and configurable gaps between windows. This feature is just eye candy, and may or may not actually aid the user by providing some visible space between windows (at the expense of some screen real estate) to make clearer the distinction between adjacent windows. What cannot be argued though, is that i3-gaps just looks better. Seriously though, it is just regular i3 but with re-sizable gaps between windows that can be turned on or off.

Debian does not have i3-gaps in their repos, just plain i3. If you are running debian, and already have i3 from the debian repos installed, and you want to use i3-gaps, I recommend uninstalling the version from the debian repos before proceeding. The reason you want to do this is that the i3-gaps binary is actually named i3, just like the non-gapped i3 from which it is forked.

I don’t know why the forked version has the same name, but that’s OK. You either want the gap option, or you don’t. If you want them bad enough, just uninstall the i3 from the repo before proceeding.

sudo apt purge i3

Before we go any further, and in the spirit of full disclosure, I installed i3 in /usr/ instead of /usr/local/.
I know, I know…the instructions that follow though will assume that you want to install i3-gaps in /usr/local/.

So, here is how to build from source and install i3-gaps on debian:

First install the dependencies:

apt install meson dh-autoreconf libxcb-keysyms1-dev libpango1.0-dev libxcb-util0-dev xcb libxcb1-dev libxcb-icccm4-dev libyajl-dev libev-dev libxcb-xkb-dev libxcb-cursor-dev libxkbcommon-dev libxcb-xinerama0-dev libxkbcommon-x11-dev libstartup-notification0-dev libxcb-randr0-dev libxcb-xrm0 libxcb-xrm-dev libxcb-shape0 libxcb-shape0-dev

Then cd to the directory where you want to download the i3-gaps source code and the run the following commands in the order shown.

git clone https://github.com/Airbladder/i3. git i3-gaps
cd i3-gaps
mkdir -p build && cd build
meson --prefix /usr/local
sudo ninja install

The meson –prefix option allows you to pick where you want to install i3-gaps. In the above example, everything will be installed in sub-directories of the /usr/local/ directory.

As I mentioned before, this binary will not be called i3-gaps, but it will be called i3.

If you are like me, and don’t use a display manager, just edit your .xinitrc file and comment out your current window manager and add the following line:

exec i3

If you are running a display manager you should be able to pick i3 from the login screen. Remember it will be called i3, not i3-gaps.

Once installed, you will need to edit your config file (~/.config/i3/config) to enable the gaps feature, since the config file that comes with i3-gaps is the same one as the default non-gapped i3 from the repo. All you need to add is in the README.md at the i3-gaps github page. Note that the i3-gaps documentation states that window titlebars need to be disabled in order for the gaps feature to work. I think that recommendation may be out of date, as I have run gaps with window titlebars enabled; but YMMV. I have since grown to love windows without titlebars though, and keep my titlebars disabled..

Here is the pertinent part of my config file, and how I have the gaps configured:

# gaps
# disable window titlebars
for_window [class="^.*"] border pixel 0

gaps inner 6
gaps outer 2

bindsym $mod+Shift+g gaps inner all set 6; gaps outer all set 2
bindsym $mod+Shift+n gaps inner all set 0; gaps outer all set 0

# Only enable gaps on a workspace when there is at least one container
smart_gaps on

# Activate smart borders (always)
#smart_borders on

# Activate smart borders (only when there are effectively no gaps)
#smart_borders no_gaps

# Hide edge borders only if there is one window with no gaps
hide_edge_borders smart_no_gaps

# What follows here is optional and defines a mode that allows you to resize the gaps on the fly.
# Press $mod1+Shift+g to enter the gap mode. Choose o or i for modifying outer/inner gaps. 
# Press one of + / - (in-/decrement for current workspace) or 0 (remove gaps for current workspace).
# If you also press Shift with these keys, the change will be global for all workspaces.
set $mode_gaps Gaps: (o) outer, (i) inner
set $mode_gaps_outer Outer Gaps: +|-|0 (local), Shift + +|-|0 (global)
set $mode_gaps_inner Inner Gaps: +|-|0 (local), Shift + +|-|0 (global)
bindsym $mod1+Shift+g mode "$mode_gaps"

mode "$mode_gaps" {
        bindsym o      mode "$mode_gaps_outer"
        bindsym i      mode "$mode_gaps_inner"
        bindsym Return mode "default"
        bindsym Escape mode "default"

mode "$mode_gaps_inner" {
        bindsym plus  gaps inner current plus 5
        bindsym minus gaps inner current minus 5
        bindsym 0     gaps inner current set 0

        bindsym Shift+plus  gaps inner all plus 5
        bindsym Shift+minus gaps inner all minus 5
        bindsym Shift+0     gaps inner all set 0

        bindsym Return mode "default"
        bindsym Escape mode "default"
mode "$mode_gaps_outer" {
        bindsym plus  gaps outer current plus 5
        bindsym minus gaps outer current minus 5
        bindsym 0     gaps outer current set 0

        bindsym Shift+plus  gaps outer all plus 5
        bindsym Shift+minus gaps outer all minus 5
        bindsym Shift+0     gaps outer all set 0

        bindsym Return mode "default"
        bindsym Escape mode "default"

If you like i3, you’ll love i3-gaps; even if you don’t love gaps, you can just turn them off and it will be just like regular i3. That is a win-win-win scenario.