i3-external-monitor

Being an awesome minimalist tilling window manager, the minimalism part means that some things in i3—like dealing with external monitors—are left to the user. This is how I handle it. #vim #plugin #snippets [Source code]

The monitors.sh script assumes there is always one internal monitor (in a laptop this would be the integrated display), and a list of external displays (VGA, HDMI, etc), at most one of which might be connected. It wraps the relevant xrand commands and changes to i3’s config file, for the following scenarios:

Internal monitor only (-i argument): disables all external outputs (connected or otherwise), if any, leaving as active only the internal monitor (in laptops, I set this to the laptop’s own monitor, usually eDP1 or similar). Any windows placed on the external display will be moved to the internal one.
External monitor only (-e argument): disables the internal monitor, and uses only the external one. If there is more than one external monitor connected, it uses the first one in the list, as per xrand’s ordering.
Clone internal monitor to external one (-c argument): clones the internal display to the external one.
Presentation mode (-p argument): uses the two monitors, and requires another argument — one of –above, –below, –right-of or –left-of — which is the position of the external monitor relative to the internal one.

NOTA BENE: if you do an -e, and then a -p, settings will be configured properly, but all existing windows will be left showning on the external monitor.

Setup

I assume that you have i3 properly configured. The first step is to run xrandr without arguments, in order to get a listing of connection ports (something like VGA1, DP1, HDMI1, …). You must detect the name of the port where your internal monitor is connected, and replace the value of the IN shell variable (line 12 of monitors.sh script) with that detected value. For example:

IN="eDP1"

Next, add the following anywhere in i3’s main config file (~/.config/i3/config for me; I usually put the variables near the beginning):

# For monitor switching.
set $DEFAULT eDP1
set $OUTPUT NONE

Replace eDP1 with the same value used for the IN variable above.

NOTA BENE: never set both $DEFAULT and $OUTPUT to the same value! All kinds of gremlins will ensue otherwise, together with a lot of flickr, as i3 will keep setting the one and only existing display, to one configuration, then to the other, then back to the first, …

Roles of each variable. (This paragraph may be skipped on a first reading.) In presentation mode (-p), which is the only mode where there are two active monitors displaying different content, the $DEFAULT variable points to the internal monitor, and the $OUTPUT to the external one. This allows setting shortcuts for moving whole workspaces from one output to the other, and also to have different configurations for the status bar/tray icons in each screen (see the section “Extras”, below). In all other scenarios $OUTPUT is set to the dummy value NONE (causing i3 to ignore the respective config blocks), and $DEFAULT is set to either the internal monitor—when using only this internal monitor (-i), or when cloning (-c)—or to the external monitor, when only this (external) monitor is being used (-e).

The following shortcuts are not strictly necessary, but become rather handy:

# move workspace to default output...
bindsym $mod+m move workspace to output $DEFAULT
# move workspace to external output...
bindsym $mod+Shift+m move workspace to output $OUTPUT

And we are done! To setup an external monitor in presentation mode, say, do:

$ sh /path/to/monitors.sh -p --above

To return to just using the internal monitor (works even if you unplugged the external one, without disabling it first):

$ sh /path/to/monitors.sh -i

Enjoy!

Extras

Still for bash, you can enable completion by placing the following in .bashrc (change ~/.bash_completion.d/ to anything of your liking; don’t forget to create it if necessary):

if test -d ~/.bash_completion.d/; then
    for profile in ~/.bash_completion.d/*.sh; do
        test -r "$profile" && . "$profile"
    done
    unset profile
fi

Now dump the following in a file named monitors.sh in that directory (~/.bash_completion.d/ or whatever else you used):

_monitors()
{
    if [[ $COMP_CWORD -eq 1 ]]; then
        WORDS="-i -e -p -c -h"
    elif [[ $COMP_CWORD -eq 2 ]]; then
        WORDS="--above --below --left-of --right-of"
    fi
    local cur=${COMP_WORDS[COMP_CWORD]}
    COMPREPLY=( $(compgen -W "$WORDS" -- $cur) )
}
complete -F _monitors monitors ./monitors.sh

Now, after re-sourcing .bashrc, you will have completion, even when invoking the command as $ monitors, i.e. as a bash alias.

Finally, when in presentation mode, I like to show, in the external monitor, a bar with less information than what I use for my internal monitor (and no tray icons). To achieve this, we use an extra bar { } block, in i3’s config:

bar {
  output                $DEFAULT
  tray_output           $DEFAULT
  status_command        i3status -c ~/.config/i3/i3status.conf
  ... rest of your regular bar settings here...
}

bar {
  output                $OUTPUT
  tray_output           none
  status_command        i3status -c ~/.config/i3/i3status-external-output.conf
  ... rest of your (perhaps more restricted) bar settings here...
}

Here i3status.conf is the regular status bar config, and i3status-external-output.conf is the restricted one (basically the same, but with some items suppressed—e.g. network information, etc.).

Circa 2017. Got feedback? Great, email is your friend!