Re: highlighting non-ASCII characters

[Ted Zlatanov]

On Tue, 23 Mar 2010 20:45:48 -0400 Stefan Monnier <address@hidden> wrote: 

SM> What I'm saying is that there are two issues: non-ASCII chars in general
SM> (which I personally don't want to display in any special manner:
SM> they're just as normal as ASCII chars), and then there are "chars that
SM> are out of place or that may not be what they look like", such as the
SM> weird "K" in the other message's "OK" (which to me, is similar to the
SM> NBSP char in that it is meant to be displayed in the same way as some
SM> other char, so we want to call the attention of the user to the
SM> difference).
...
SM> I don't insist on using escape-glyph for those chars, indeed (I don't
SM> really care which face is used for them).  What I care about is figuring
SM> out how to define programmatically "chars that are out of place or that
SM> may not be what they look like".

How about this:

show-nonascii-characters: t, 'majority-paragraph, majority-line, 
                          'minority-line, 'minority-paragraph, 
                          'suspicious, a function, or nil (default) 

show-nonascii-characters-face: customizable from a list of presets,
escape-glyph, or a custom face

The rules:

t = always

majority-paragraph = highlight when they are 0-90% of the paragraph

majority-line = ditto for the line

minority-line = highlight when they are 0-20% of the line

minority-paragraph = ditto for the paragraph

suspicious = 3-5 characters per visual line

function = passed a list of regions of non-ASCII characters

nil = the default, don't highlight

I'm sure we'll tune this but as someone who writes non-ASCII characters
a lot, this would make sense.  I'd personally use t but I can see how
that could be annoying.  I think you're in favor of 'suspicious.

The idea is to make this easy to set up and available in any mode or
globally.  It's easy for an experienced user to set up something
atrocious, but good choices for the colors and the rules are, I think,
the tricky and valuable part.

Ted