Assign workspaces on i3 to multiple displays

Question

I've switched on using i3 on my Linux laptop. I'm usually using only the laptop's internal monitor (display eDP1), but when I'm at work I tend to connect a secondary monitor to my computer's HDMI port (display HDMI2). So far, I've made this work fine by adding these commands to my i3 config file:

# use workspaces on different monitors
workspace "1: P1" output eDP1
workspace "2: P2" output eDP1
workspace "3: P3" output eDP1
workspace "4: P4" output eDP1
workspace "5: P5" output eDP1
workspace "6: S1" output HDMI2 
workspace "7: S2" output HDMI2
workspace "8: S3" output HDMI2
workspace "9: S4" output HDMI2
workspace "10: S5" output HDMI2

# add HDMI monitor when connected
exec --no-startup-id xrandr --output HDMI2 --right-of eDP1
bindsym $mod+m exec --no-startup-id xrandr --output HDMI2 --auto --right-of eDP1

In other words, when I connect my HDMI display I just press Mod+M to get i3 to detect it, place it right of my primary display, and delegate 5 named workspaces (6-10) to it.

Here's the problem: At home, I have another monitor that I can connect with VGA (display DP2). I can run the xrandr command above to place this display to the right of my primary display as well, but I can't get the workspaces to be assigned to this display by default, unless I replace the rules I already have for my HDMI monitor. I would like both these workspaces to work the same no matter which monitor I use, so this is not an option.

TL;DR Is there a way to assign workspaces to two different displays, depending on which display is connected (assuming they never will be connected at the same time)?

Answer 1

You can't assign multiple outputs to single workspace, see: https://github.com/i3/i3/issues/555

So the only way is to change i3 config dynamically. You could assign to hotkey script that will be doing 2 things: changing monitor outputs with xrandr and moving workspaces with i3-msg:

xrandr --output DP2 --auto --right-of eDP1
i3-msg "workspace 6, move workspace to output DP2"
...
i3-msg "workspace 10, move workspace to output DP2"

With above script you will move 6-10 workspaces to DP2 and end up staying on workspace 10.

Update 2019: Multiple outputs assignment was implemented starting from v4.16, see https://i3wm.org/docs/userguide.html#workspace_screen. Now you could use them like that:

workspace "6: S1" output HDMI2 VGA

The first available output will then be used.

Answer 2

According to the user's guide, syntax:

workspace 1 output eDP1
...
workspace 6 output HDMI2 VGA

should work.

Or you may define primary output on your machines, if not set (xrandr --output <output> --primary), and use this syntax:

workspace 1 output primary
...
workspace 6 output secondary