RE: I'd like Emacs to display a big (but short) "pop up" text

[Drew Adams]

> I'd like to display a "pop up"/"tip", i.e., a short text (a few
> characters).  The thing is, I want it to be visible: large font,
> preferably centered on the screen.  My use case is demoing Emacs, and
> before showing the effects of e.g. C-x 2, I'd like to show
> a big-lettered "C-x 2" on the screen.  It would be nice to use something
> like the blocks in M-x tetris to build the letters, or anything else
> that would clearly show "C-x 2" or whatever keychord I'm showing.

I created ‘showkey.el’ for just this.  It shows keys and other events
as you use them.

You can tailor the behavior to ignore given event types for display.
There are 2 ways to show keys:

* ‘showkey-tooltip-mode’ – Show only the last key used, in a tooltip.
  Refreshed with each such event.

* ‘showkey-log-mode’ – Show a log of such events, in a separate frame.
  Refreshed with each new event.  On top of other frames, without
  stealing focus.

Description: https://www.emacswiki.org/emacs/ShowKey
Code: https://www.emacswiki.org/emacs/download/showkey.el (or MELPA)