Here's the next part of our emoji project. In this video, we make the magic automatically happen. That is, when the user types an emoji in quotes - like 🐘, Emacs will automatically replace it with the emoji, 🐘.

Now, mind you, the way we're doing it isn't the best way. In fact, after I posted the previous video, Micky Peterson linked to an article he wrote on using input methods to insert emoji. Using input methods would be much cleaner but this series isn't necessarily about doing something the best way but rather exploring and playing with elisp in a way that hopefully will empower readers and viewers to build whatever they need.

The magic to making our version work is by using Emacs Hooks. You can think of hooks like events if you've done GUI or web programming. In a web interface you might make a button and set an event so that whenever the button is pressed some function is called or you make a text input field and set an event so that whenever the content of that input field changes, some function is called.

Hooks are like that and there are tons fo them.

In the video, I use this simple example:

  (defun redact ()
    (save-excursion
     (goto-char 0)
     (replace-string "secret" "REDACTED")))

  (add-hook 'before-save-hook #'redact)

The function simply replaces all occurrences of the string "secret" and changes it to "REDACTED." The before-save-hook runs associated functions before saving a file so in the above code sample, once the hook is added, whenever you save a file, the redact function will run and all occurrences of "secret" will be changed.

This is a silly example but a more useful one for this hook would be to run a code autoformatter.

To remove the hook we would use:

  (remove-hook 'before-save-function #'redact)

Note that the add-hook function also has options to decide if the hook is for the buffer or everywhere.

For the emoji project, we'll use the after-change-functions hook which lets us call a function whenever the buffer is changed.

The video goes into all the details.

Next up, we'll see how we can overlay an emoji over text instead of replacing.