bug#57072: [BUG] update-glyphless-char-display and variation selectors

[Eli Zaretskii]

merge 57073 57072
thanks

> From: Axel Svensson <svenssonaxel@gmail.com>
> Date: Tue, 9 Aug 2022 10:38:30 +0200
> 
> IIUC the documentation to glyphless-char-display-control, any of the 
> character groups can be assigned any
> of the display methods.

But not every glyphless character has an acronym, so this is not a
bug.  You are suggesting an enhancement (which is fine).

> First bug + patch:
> Using update-glyphless-char-display to choose to display variation-selectors 
> as acronyms does not work
> since these codepoints are missing from char-acronym-table.
> The attached patch attempts to fix this and succeeds for U+FE00..U+FE0E but 
> fails for U+FE0F.

Why are the acronyms you propose so long?  Why not use "VS01".."VS16"
instead?  Shorter acronyms are an advantage, since they will be
displayed in a more legible way.

> Second bug:
> It seems that U+FE0F will not at all respect glyphless-char-display, instead 
> always showing as an empty
> box.
> This I have not solved.

Please show a recipe for that starting from "emacs -Q".

Thanks.