Years ago when setting up i3 on my FreeBSD laptop, I used ImageMagick’s import(1) to take screenshots of my X windows and save them for the future (my screenshot collection goes back to 2009; like a photo collection but of my online identity, but that’s another topic for another day).

Using import(1), there is no way to cancel an intiatied screenshot selection: you must screenshot something for the selection to close. So what if I ended up not wanting to screenshot anything after starting a screenshot? I couldn’t just bind the Escape key on my keyboard to kill import, since I use the Escape key for many other things like readline.

The problem at hand is therefore: since the Escape key is already used by programs other than import(1), how can we exclusively bind the Escape key to execute a specific command (kill) when a screenshot is being taken using import(1)?

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i3’s “binding modes” seems to be the solution here. As the manual states:

You can have multiple sets of bindings by using different binding modes. When you switch to another binding mode, all bindings from the current mode are released and only the bindings defined in the new mode are valid for as long as you stay in that binding mode.

To achieve our objective, we therefore:

1. Bind the Mod4+Shift+4 key combination to both switching the a new mode named “screenshot” – and execute a script screenshot.sh.
2. Inside the “screenshot” mode, bind the Escape key to go back to the “default” mode and kill /usr/local/bin/import.
3. Create a screenshot.sh script which calls /usr/local/bin/import to take the actual screenshot.

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The i3 config of this solution looks as such:

bindsym Mod4+Shift+4 --release mode "screenshot" ; exec ~/scripts/screenshot.sh
mode "screenshot" {
  bindsym Escape --release mode "default" ; exec kill $(pgrep -f /usr/local/bin/import)
}

and the screenshot.sh looks like:

#!/bin/sh

DATE=`date +%Y-%m-%d:%H:%M:%S`
/usr/local/bin/import ~/Pictures/Screenshots/Screenshot-"${DATE}".png && \
  ln -fs ~/Pictures/Screenshots/Screenshot-"${DATE}".png /tmp/latest-screenshot.png
exit_code=$?

i3-msg mode "default"
exit $exit_code

i3-msg mode "default" in the script ensures that when a screenshot is taken, i3 moves back to the “default” mode. The mode "default" in the bindsym Escape of the screenshot mode is not really necessary, but it is added for redundancy.

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These days, I use scrot(1) for screenshots, which comes with inbuilt functionality to exit the screenshot selection when any key is pressed:

bindsym Mod4+Shift+4 --release exec scrot -s /home/user/Pictures/Screenshots/Screenshot-%Y-%m-%d:%H:%M:%S.png -e 'ln -fs "$f" /tmp/latest-screenshot.png'

However, I still use i3 modes to set up program-specific keybinds as outlined in this post elsewhere.