Re: On the masking of undisplayable characters

[Eli Zaretskii]

> Date: Mon, 6 Jul 2015 20:57:08 +0100
> From: Artur Malabarba <address@hidden>
> Cc: emacs-devel <address@hidden>
> 
> > What characters are you talking about, specifically?
> 
> Round quotes were displayed as hard quotes. The reason this happened on my pc
> was a bug, but I understand that for systems that really can't display them
> this is what will happen. 
> 
> I didn't check whether this applies to any other characters. I was just
> surprised to find out the file was not being displayed as-is without so much 
> as
> a notice.

It should happen only with quotes, and presumably only in
documentation-related buffers.  The rationale is that we cannot afford
showing illegible documentation to users just because their terminal
is incapable of displaying these important characters.

I suggested to limit this to windows showing *Help* buffers, but it
was decided to wait until someone complains.

> > It's hard to respond without knowing the details. Most of the uses of
> > display tables I know of are there for ages, so adding some kind of
> > message about that now would seem inappropriate. (And when exactly do
> > we display that message? when the character is first displayed?)
> 
> When visiting the file and when the character is typed for the first time,
> would be an option.

Not really: the display engine doesn't examine any of those
characters, until they are on or very near to the visible portion of
the buffer.

> > the glyphless-char-display feature,
> 
> I don't know which characters are affected by this.

Those that cannot be displayed by any fonts.