Re: utf8 char display in buffer

[Lennart Borgman]

On Sat, Jun 13, 2009 at 3:36 AM, Miles Bader<address@hidden> wrote:
> Lennart Borgman <address@hidden> writes:
>> Ken, I think this is a good idea so I have sent this along to Emacs devel.
>>
>>> Yet emacs puts a little box in the place of a character it cannot find
>>> (or, per your explanation) possibly confused about.  The fact remains
>>> that the little box is not a correct rendering of the code.  It is an
>>> error... at least it is for me, because that's not what I typed in.  So
>>> it is an error.  As an error, there should be a corresponding error
>>> message, hopefully one (or more) which would help diagnose the problem.
>
> An "error message" _when_?  Whether a character is displayable or not
> isn't known until display time, and error messages for display issues
> are generally a very bad idea.  For some display errors, the display
> code will put messages in the *Messages* buffer (though they aren't
> displayed to the user), but even that must be done with careful
> consideration; currently they typically indicate that something
> seriously screwy is going on (and a non-displayable character, however
> annoying, isn't "seriously screwy").
>
> If an "error message" were displayed, what would it say?  The only thing
> I can think of is "no font could be found to display character FOO", but
> that fact is already obvious from the little box.  Given no extra
> detail, is a message even useful?
>
> Maybe some sort of _once-only_ pop-up buffer note to the user saying
> "little boxes indicate characters for which a font could not found; see
> info manual section X.Y for details on blah blah"?  I suppose that could
> help some people, but such a thing, even if once-only, would probably be
> pretty annoying to non-complete-noob users, so ...

Yes, I know you have to be careful with error messages in a case like
this, but giving some type of information (like the one you suggested)
the first time in an emacs session when such a little box is shown was
what I had in mind.