RE: Redisplay hook

[Drew Adams]

> >> Additionally, since Emacs is driving, I can record plenty of
> >> per-frame data, such as which key is being pressed with each frame.
> >> Here's an example, which was fairly easy to assemble using this new
> >> hook and a bit of ImageMagick:
> >> http://web.mit.edu/cpitcla/www/emacs-screencast-annot.gif (it may
> >> take a bit of time to load). What do you think of the result?
> >
> > This is great and I would love to see this as a package and see it
> > explained in more detail..  A simple way to capture Emacs
> > screencasts, potentially with an audio overlay, would lead to many
> > more demonstrations of Emacs packages leading to broader
> > understanding and usage.
> 
> Thanks Bob :) Here's a quick outline of how it's done; hopefully we can
> implement the necessary hook, and then I'll make an ELPA package out of it.
> 
> Essentially, my code adds two hooks:
> - A pre-command-hook, to update a variable tracking (this-command-keys-
>   vector)
> - A post-display-hook, to capture screenshots.

Not at all related to the redisplay feature (hooks) being discussed,
but FWIW here is another key-showing approach.

By default it shows also the commands keys are bound to, but this is
controlled by option `showkey-key-only-flag'.  You can show keys using
a tooltip (`showkey-tooltip-mode') or log them in a separate frame
(`showkey-log-mode').

https://www.emacswiki.org/emacs/download/showkey.el