Re: Suggest installing more fonts?

[Gregory Heytings]

> > Another thought on this: to avoid "looking unprofessional", a help-echo 
> > property could be added on these characters, saying something like 
> > "Warning: no font installed for this character".  So the user would see 
> > an ugly (but often recognizable) character, and at the same time would 
> > be warned that they need to do something to see it better.
>
> Yes, Lars suggested that as well.  But we have to be careful: too many 
> such properties or overlays will slow down redisplay.  Also, we'd need 
> to see how to do this technically, since characters that have no fonts 
> are discovered during redisplay.  Perhaps some jit-lock registered 
> function could detect them after redisplay, and put the properties on 
> some of them (which ones?).

I think I see what you mean: characters that have no fonts are discovered 
during redisplay, and at that moment it's too late to add text properties, 
which are not supposed to change anymore.  It might be possible to add a 
special help-echo like property that would be added at the moment these 
characters are discovered, for example in produce_glyphless_glyph().

I don't think there would be "too many" such properties, it seems safe to 
assume that in general such characters follow each other and form a 
"block", and a single text property would be enough for one such block.