bug#45184: 26.1; Private Unicode plains 15 and 16 seem not supported

[Janusz S. Bień]

On Fri, Dec 11 2020 at 22:10 +02, Eli Zaretskii wrote:
> severity 45184 wishlist

This is a bug report, not a feature request.

> thanks
>
>> From: jsbien@mimuw.edu.pl (Janusz S. Bień)
>> Date: Fri, 11 Dec 2020 18:55:51 +0100
>> 
>> I intend to use plains 15 and/or 16 for the historical variant of Polish
>> letters. An appropriate font is understand preparation, but not yet
>> available publicty.
>> 
>> When the font was installed in ./loca/share/fonts, a QT program found it
>> and displayed the characters correctly. Emacs, to the contrary, for
>> 
>> character: 󰀀 (displayed as 󰀀) (codepoint 983040, #o3600000, #xf0000)
>> 
>> reports "no font available".
>
> That's because Emacs has no idea that you are using SPUA planes for
> Polish.

The fact that I want to use the characters for Polish is irrelevant.

> You need to tell Emacs about that by augmenting your fontset.

The PUA from the Basic Multulingual Plane are used by me for years and
do not require doing anything with the fontset. For example, LATIN SMALL
LETTER LONG S WITH FLOURISH (coming from the Medieval Unicode Font
Initiative) is displayed without problem and the appropriate font is
found automatically:

            character:  (displayed as ) (codepoint 59575, #o164267, #xe8b7)
    xft:-psbk-Junicode-normal-normal-normal-*-15-*-*-*-*-0-iso10646-1 (#x94C)

The same should happen for the characters from plains 15 and 16. However
now even the explicit selection of the appropriate font doesn't help.

> (And even after you do that, there could be problems, because Emacs
> doesn't treat PUA ranges of Unicode codepoints as characters.)

Really? What do you exactly mean? My experience contradicts this
statement.

I think the Emacs code just for some reason limits the range of the
Unicode characters, and the limitation should be removed.

Regards

Janusz

-- 
             ,   
Janusz S. Bien
emeryt (emeritus)
https://sites.google.com/view/jsbien