bug#29837: UTF-16 char display problems and the macOS "character palette"

[Eli Zaretskii <eliz@gnu.org>]

> Date: Sun, 24 Dec 2017 16:00:53 +0000
> From: Alan Third <alan@idiocy.org>
> 
> It’s easy enough to bring it up (patch attached) but some special
> characters are put into Emacs incorrectly. I think the problem is that
> we have multi code‐point UTF‐16 characters, and when they are ‘typed’
> into Emacs they are entered as individual 16 bit code‐points and are
> therefore displayed as a series of blank spaces.
> 
> An example is '🢫' (RIGHTWARDS FRONT-TILTED SHADOWED WHITE ARROW). If I
> enter it using C‐x 8 RET, it appears correctly, but if I use the
> character palette it shows up as two blank spaces. Describe-char
> reveals these to be HIGH SURROGATE-D83E and LOW SURROGATE-DCAB, in
> that order.

You need to tell Emacs that keyboard input is in UTF-16.  Did you try
"C-x RET k"?

> (Another minor irritation is that some characters (like pointing
> hands) seem to insert the desired character then follow up with
> VARIATION SELECTOR-15. I assume this is supposed to tell us what
> colour we want the hand? If so should it be displayed?)

Emacs doesn't yet support variation selectors.  Patches to add that
are welcome (I guess it will need some change in our interface with
font back-ends?).