Re: Can watermarking Unicode text using invisible differences sneak through Emacs, or can Emacs detect it?

[Richard Stallman]

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  > > I think there are only around 20 diacritics.

  > You are thinking of some subset, I think.  The real number is more
  > like 80,

I am amazed.  Where can I see a list that shows more of them?

  >   That's a great simplification from a table
  > > of hundreds of elements, set up by hand.

  > Setting by hand was already done, and we have it in latin1-disp.el so

Do you mean, the table that presents a-with-breve-and-tilde as `a)?'?
I don't think that works well.

  > > I don't follow you here.  In particular, what does "complete
  > > equivalent" mean?

  > For example, "o?'" instead of "o" + "?" + "'" (to emulate ?\ṍ).

I don't understand the difference between "o?'" and "o" + "?" + "'".
They look like two ways of describing the same sequence of three characters.
Though ? would never make me think of tilde unless you told me.

                                                                     With
  > the former, you see the entire string that will be shown; with the
  > latter, you need to imagine it

I can't follow that, since you're talking about two things that look
identical to me.

  >   What would you do with the likes of ?\ǿ (which we currently
  > represent as "o/'")?  Its base character, ø, doesn't have a
  > decomposition in Unicode.

For my terminal, I'd like it to send ø literally since my terminal
can display that.  `ø'' would be a good way to display it.
But on a terminal that can't display ø, `o/'' would be a good choice.

  > > Not on a Linux console, I think.  When I have f and i in the buffer,
  > > Emacs does not convert them into a ligature.  The only time it has to
  > > try to deal with a ligature is when there is a Unicode ligature
  > > code point in the buffer.

  > Once again, on a TTY frame Emacs does NOT produce the ligatures nor
  > combine base characters with the diacritics.

You have told me this several times, and I believe you.  But how does
it relate to the case I am talking about?  I don't see a relationship.

I was looking at a buffer containing a ligature character.  It must
have come from a message or file that I looked at in that buffer.  I
suppose Emacs did not _produce_ it, but it was in my buffer and I had
to use C-u C-x = to see what it was.


-- 
Dr Richard Stallman (https://stallman.org)
Chief GNUisance of the GNU Project (https://gnu.org)
Founder, Free Software Foundation (https://fsf.org)
Internet Hall-of-Famer (https://internethalloffame.org)