Re: Suggest installing more fonts?

[Eli Zaretskii]

> From: Stefan Monnier <monnier@iro.umontreal.ca>
> Cc: larsi@gnus.org,  emacs-devel@gnu.org
> Date: Fri, 16 Oct 2020 15:37:40 -0400
> 
> >> - Does the problem only affect Emacs and not other applications?
> >>   If so why?
> > AFAIK, "most other applications", at least those I could investigate,
> > come with fixed lists of fonts to use for each script.  These lists
> > are maintained for each OS and are adjusted as the OS version and the
> > fonts change.  This method has its advantages and also its
> > disadvantages; I think both are quite clear.
> 
> But then it means that "installing more fonts" is not really the solution
> that the user needs to follow, right?

I'm not sure how you reached this conclusion.  Are you talking about
Emacs or are you talking about other applications?

If an application expects to see some font that is not installed, the
user should go out and install it, otherwise the characters will not
be shown.  Happened to me with applications other than Emacs a few
times.

The main difference between what Emacs does and what the other
applications do is that the other applications specify proprietary
fonts usually available on the target system, while we don't.  the
disadvantage of what we do is that Emacs might find a font that is not
the best one for supporting a given block of Unicode codepoints.

> >> - Do users immediately run to search the internet for answers without
> >>   even trying to interact any further with their Emacs instance to
> >>   investigate the problem first?
> >> - If they do interact with Emacs, what do they do?  Do they move the
> >>   mouse over the tofu?  Do they look for some help some other way?
> > The rational thing to do is to use "C-u C-x =", see the script of the
> > problematic character(s), and then find and install some font that
> > covers those characters.
> 
> But from what you said above it's not just a question of installing
> fonts (since what you wrote before suggests that the same problem
> doesn't affect other applications on the same system).

See above.

> Also I suspect that this requires non-trivial knowledge:
> - `C-u C-x =`, which most beginning Emacs users won't know.
> - The notion of "script" and how to find it out.
> - How to know which font covers which script.
> - Potentially how to tell Emacs which font to use for which script.

Which is why we are having this conversation.

The idea behind what Emacs does is that the system is already
configured to display the script that the user wants to use in Emacs.
Where this is not true -- and I'm not sure I have a clear picture of
why this could happen -- what we do is insufficient.

Btw, one problem I think makes this issue more severe than it has to
be is that there are many fontset customizations floating out there
which people copy into their init files without understanding what
they do, and those customizations are either dangerous or plain
incorrect, and get users into trouble wrt fonts.  Another related
problem is that people install all kinds of fonts that could claim
support for some script, but in fact don't have a decent support for
it.  These two issues probably call for a "M-x fontset-analyze"
command, if we have anyone aboard capable of writing it.