Re: master 15afa72460b: Fix 'script-representative-chars' for the 'han' script

[Po Lu <luangruo@yahoo.com>]

Eli Zaretskii <eliz@gnu.org> writes:

> Note that I said "if you remove those characters".
>
> If you did note that, then does it mean when U+2F75 needs to be
> installed and the current font for han doesn't support it, Emacs will
> never try to look for _another_ font which supports han characters?
> Or will it try, but always fail?

How do you mean?  During Emacs's search for a suitable font, it is yet
to decide what is the "current font for han."

>> > IOW, I'm interested to know what happens on GNU/Linux if more than one
>> > font is available that together cover both the "usual" han characters
>> > and those additional ones which you think we should remove from
>> > script-representative-chars, but neither of these fonts supports all
>> > of those characters.  Can Emacs solve this by itself on GNU/Linux, or
>> > does it need "help" from the user's customization of the fontset?
>> 
>> Probably the latter, unless `han' is divided into scripts for
>> characters, obsolete characters, radicals, and the like.
>
> That is again quite disappointing, since I always thought font
> backends based on Fontconfig can do a better job, because (AFAIR)
> Fontconfig caches the font information and makes it available for
> programs that search fonts covering specific characters.

Fontconfig is capable of this, but not telepathy.  If Emacs submits
multiple requests for such and such a list of characters, ftfont cannot
telepathically deduce that in the one instance it should only consider
those characters which are in common usage, while in the other radicals
or obsolete characters.

> What you describe happens on MS-Windows, but there we don't have a way
> to test whether a font supports a character without actually loading
> the font (the 'has_char' backends method always fails).