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

[Richard Stallman]

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  > How did that ligature get written to the screen?  Was it present
  > literally in some text that Emacs displayed?

It was in the buffer.  That is why I was able to examine it with C-u C-x =.
I suppose it was present in text that I visited in Emacs.

  >   So let's please leave the literal fi
  > display alone, because it will take us far away from the original
  > issue.

Thank you for clearly describing these two cases.
I did not know that the ligature case people were discussing
was limited to composition of characters -- that it was different
from the case of displaying a ligature character actually in the buffer.
What people said was sketchy and I had to try to fill in what
was not said.

  >   When several characters are supposed to
  > be composed on a text-mode display, Emacs simply writes them to the
  > terminal one after another, and expects the terminal to display them
  > as a ligature.  The only difference between what Emacs does in this
  > case and what it does when no character composition is expected is
  > that in the former case Emacs expects the terminal to produce just one
  > glyph that takes just one column on display.

In that case, I think I it would be good to be able to tell Emacs,
when using a text-only terminal, not to try to compose ligatures.
Not to expect that sequence to display as one column.  Is that possible?

-- 
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)