Re: Suggest installing more fonts?

[Gregory Heytings via "Emacs development discussions." <emacs-devel@gnu.org>]

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>>> I know.  I was just pointing out that there are several problems 
>>> (missing fonts is one of them, but not the only one), so before trying 
>>> to solve "the problem", we should be clear about which one it is and 
>>> try and figure out whether it's indeed the most common.
>>
>> A user has (usually) no idea of these "several problems", and knows 
>> even less how to fix them.  For such users the problem is simply "Emacs 
>> displays gibberish".  That is "the problem" IMO.  Everything else are 
>> technicalities that very few know/understand/have the patience to deal 
>> with.
>>
>> So IMO for these users it would be much better to display characters 
>> with a low-resolution font, together with a warning (and perhaps a 
>> pointer to a short guide) (as a help-echo and/or in the echo area), 
>> instead of a tofu.
>
> Then the problem will become "Emacs uses an ugly font where other apps 
> don't", and we are none the wiser.
>

_All_ apps have that problem, it is _not_ an Emacs-specific problem.  I 
provided two examples with apps that have a lot more available manpower 
than Emacs (Chromium and VS Code) in which that problem also exists. 
What _all_ apps do in that case is to display a tofu.

>
> IMO, we should try fixing whatever problems are there (and AFAIU there's 
> more than one) without using ugly fonts.  For example, problems with 
> displaying Emoji are due to some missing infrastructure (see a separate 
> discussion about that), and once we add that, the result will be much 
> better than anything you could get with Unifont.
>

It's a very complex problem, which is why it exists in all apps.  I don't 
know a single app in which that problem does not exist.

FWIW, here is my solution for Emojis (on Debian, after installing the 
fonts-noto-color-emoji package):

fc-match --format='%{charset}\n' NotoColorEmoji | tr ' ' '\n' | grep '^[^-][^-][^-][^-]' | grep -v '^200d$' | sed 's/^/#x/;s/-/ . #x/;s/^\(#[^#]*#[^#]*\)/!(\1)/;s/^\(.*\)$/(set-fontset-font "fontset-default" \1 "NotoColorEmoji")/' | tr '!' "'"

This creates 154 calls to "set-fontset-font", and as a result 
https://unicode.org/Public/UNIDATA/emoji/emoji-data.txt is displayed 
nicely by Emacs.  I'm sure you will tell me that you don't like that 
solution ;-)  But I doubt it is possible to do really better, because 
Emojis are scattered across the whole Unicode code space.

>
> IOW, using Unifont is simply a kind of admission of defeat: we don't 
> really know why Emacs doesn't find a good font, so we take the easy path 
> of providing _some_ font that will always work, albeit show ugly glyphs. 
> I see no need to declare defeat, as we have facilities in Emacs to solve 
> these problems in a better way, once we understand them.  We should 
> therefore try to understand the problems better, and once understood, 
> solve them properly.
>

The meaning of my proposal was, in fact, the exact opposite of an 
admission of defeat, it was to make Emacs better in that respect than all 
other apps.  Displaying a tofu is an admission of defeat, and it's what 
all other apps do.  They say to the user: "I don't know how to display 
that character, so I just give up without giving you any clue." 
Displaying a bitmap glyph with a warning message is doing something 
better: the users see the characters and get an indication on what they 
could do to see them better.

Another example: I have no fonts to display tamil characters on my 
computer.  Which means every app, including Emacs, displays tamil 
characters as a sequence of tofus.  I attach three pictures of the same 
short tamil text displayed by Emacs, one with its current behavior 
(tamil-no-font.png), one if it used Unifont as a fallback 
(tamil-unifont.png), and one if a proper tamil font (the Debian package 
fonts-lohit-taml) is installed (tamil-good-font.png).  I do agree (of 
course) that tamil-good-font.png is better than tamil-unifont.png, but I 
really can't understand how tamil-no-font.png could be considered better 
than tamil-unifont.png.

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