presentation_workspace.sh

#!/bin/bash

# Names of the displays you want to use for presentation as well as mirroring of said presentation screen.
# They can be easily read from arandr, or listed using `xrandr --listmonitors`
PRESENTATION_DISPLAY="DP-1"
MIRROR_DISPLAY="DVI-I-1"

# These variables depend on how you arranged your screens using arandr/xrandr.
# To Verify/Correct them, open arandr, arrange your screens as you prefer, export the command
# and then read the "--pos" value for the desired mirror and presentation output/display.
MIRROR_ORIG_UPPER_LEFT="1920x1392"
PRESENTATION_UPPER_LEFT="0x0"

# Space-separated list of workspaces you bound to the presentation display/output
# using `workspace <num:name> output <display>`, as you are referring to them in the i3 config
PRESENTATION_WORKSPACES='11:TV'


TARGET_WORKSPACE=$1

# The below command automates extraction of the output resolution. However, it takes too long due to long xrandr response times.
# Therefore, reading the resolution once (using the command) and then manually writing it into this variable is probably preferrable.
# Alternatively, you could also setup your presentation display with --mode 1920x1080 using xrandr so the resultion I put below is correct from the get-go (assuming the display supports that high resolution).
# presentation_output_resolution=$(xrandr | grep "$PRESENTATION_DISPLAY" | cut -d' ' -f3 | cut -d'+' -f1)
presentation_output_resolution="1920x1080"


# Underlying Idea: Overlay mirror display onto presentation display and scale it as necessary whenever presentation workspace is chosen
RESTORE_COMMAND="xrandr --output $MIRROR_DISPLAY --pos $MIRROR_ORIG_UPPER_LEFT --scale 1"
MIRROR_COMMAND="xrandr --output $MIRROR_DISPLAY --pos $PRESENTATION_UPPER_LEFT --scale-from $presentation_output_resolution"

focused_workspace=$(i3-msg -t get_workspaces | python3 -c "import sys,json
for workspace in json.load(sys.stdin):
    if workspace['focused']:
        print(workspace['name'])
        break")


if [[ $TARGET_WORKSPACE == $focused_workspace ]]; then
    exit 0 # Don't do anything when targeting already focused workspace. Workspace back-and-forth wouldn't be possible, since we don't know whether this sends us back to a normal or a presentation workspace.
    # TODO: Idea: Read out workspace back_and_forth target, set this as the new target workspace and continue script with that
fi

[[ " $PRESENTATION_WORKSPACES " =~ .*\ $focused_workspace\ .* ]]
already_on_presentation=$? # exit status (i.e. here truth value) of previous command/conditional expression


if [[ " $PRESENTATION_WORKSPACES " =~ .*\ $TARGET_WORKSPACE\ .* ]]; then # Check if targeted workspace is a presentation workspace. Taken from https://stackoverflow.com/a/46564084
    if [[ $already_on_presentation == 1 ]]; then
        # We are coming from a normal workspace. Setup screen before switching to new workspace.
        eval $MIRROR_COMMAND
    fi
    i3-msg workspace $TARGET_WORKSPACE
else
    # We are targetting a normal workspace
    if [[ $already_on_presentation == 0 ]]; then
        eval $RESTORE_COMMAND
    fi
    i3-msg workspace $TARGET_WORKSPACE
fi