Re: UTF-8 input [was Re: PATCH: zle_params.c]

[Peter Stephenson <pws@csr.com>]

Bart Schaefer wrote:
> On Jan 30,  1:07am, Peter Stephenson wrote:
> } Subject: Re: UTF-8 input [was Re: PATCH: zle_params.c]
> }
> } I thought of the following: self-insert could take a single character,
> } as at present, and then test if it was the initial part of a multibyte
> } character.  If it was, it could read the rest; we might need a timeout to
> } avoid an infinite hang on systems that didn't do multibyte input
> } properly
> 
> This would mean what, in terms of binding other functions to wide chars?
> That they'd behave like escape sequences do now?  I would think you'd
> want to decide whether the input is a wide char at a lower level than
> that.  Otherwise don't you have issues if what the user really means to
> bind to self-insert is a single-byte character that happens to have the
> high bit set?

Hmmm... you mean that on a system where mbrtowc() reports that a
single-byte character is incomplete, the user might nonetheless want to
insert a single-byte character onto the command line?  That's certainly
not something I'd thought of.  However, I'm not sure I see what this is
doing.  If mbrtowc() etc. are confused, which in this case they must be
(it's the only way the user's intention can disagree with what the
proposed mechanism is doing), how can we handle the later stages of
character processing successfully?  When outputting, do we ignore the
fact that wctomb() failed on this character (as it must), reset the
shift counter (for safety) and carry on?  In other words, are you
supposing this is some kind of fallback in case the locale isn't set
correctly, e.g. it's set to UTF-8 but on an xterm with character set
ISO-8859-1?

> It seems to me that some stage of the input process has to be "told"
> that the input stream is UTF-8 rather than e.g. iso-8859-something.  If
> it's the widget level that's going to handle that [*], I think it'd be
> most useful to create a self-insert-multibyte which does in fact wait
> indefinitely (or at least, longer than the normal escape-sequence key
> timeout) for the "rest" of a multibyte character after the first byte is
> seen, and feep if it doesn't get something recognizable as the rest.

That's perfectly workable, but the question above about self-insert
remains.

-- 
Peter Stephenson <pws@csr.com>                  Software Engineer
CSR PLC, Churchill House, Cambridge Business Park, Cowley Road
Cambridge, CB4 0WZ, UK                          Tel: +44 (0)1223 692070


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