Re: ignoring control characters in character width

[Eli Zaretskii]

> Date: Tue, 5 Sep 2023 20:19:40 +0200
> From: Patrice Dumas <pertusus@free.fr>
> Cc: bug-texinfo@gnu.org
> 
> On Tue, Sep 05, 2023 at 09:09:18PM +0300, Eli Zaretskii wrote:
> > > Date: Tue, 5 Sep 2023 20:01:53 +0200
> > > From: Patrice Dumas <pertusus@free.fr>
> > > 
> > > Currently, when counting the width of a line of character, we count
> > > control characters that are also spaces as having a width of 1.  I think
> > > that it is not good, as control characters either should not have a
> > > width, for end of line, form feed, carriage return, or have a width that
> > > is not well defined for vertical and horizontal tab.  I suggest to
> > > consider all the control characters as having a width of 0.  This will
> > > be consistent with libunistring u8_strwidth, which I intend to use in C
> > > code equivalent to perl code.
> > 
> > Please define "control characters" for this purpose.  Some of them are
> > definitely not zero-width, for example, TAB.
> 
> Characters whose unicode codepoints in decimal are in the range 0 to 31,
> and also 127 (Delete).  This includes the horizontal tab.  It
> corresponds to the [:cntrl:] character class.

Then I guess I still don't understand: how is TAB a zero-width
character?

> > Also, depending on how control characters are displayed, their width
> > could be even 4, for example if they are displayed as \nnn octal
> > escapes.
> 
> It is in a context where they are displayed as encoded bytes.

So what is the context of this discussion, if it is not display of
bytes?  I really don't understand, could you elaborate?

Control characters can also be displayed as ^C, for example, in which
case they take 2 columns.