Re: Character encoding / poor man's letterspacing

[Aaron Hill]

On 2019-03-11 9:56 am, Urs Liska wrote:
> Hi,
>
> I've written a poor-man's implementation of a simple \letterspaced
> markup command:
>
> #(define-markup-command
>   (letterspaced layout props text)(markup?)
>   (let*
>    ((chars (string->list text))
>     (dummy (ly:message "Chars: ~a" chars))
>     (spaced-text
>      (string-join
>       (map string chars) " ")))
>    (interpret-markup layout props
>      (markup spaced-text))))
>
> However, this scrambles umlauts and presumably other UTF-8 characters
> as you can see with
>
> {
>   s1 ^\markup \letterspaced "Täst"
> }
>
> =>Chars: (T � � s t)
>
> Obviously the characters are wrongly en/decoded along the way, which
> makes me think whether I have simply forgotten an encoding setting
> somewhere (although I have no idea where and how I should include
> that) or whether that whole routine is totally clumsy.

It is my understanding that proper Unicode support is not in Guile 1.8.  
As such, I believe string->list will not understand that multiple bytes 
could represent a single codepoint.  Also, in Guile characters values of 
the form #\nnn are limited to 256 possible values (#\000 to #\377).  If 
you try to specify a larger value, it just wraps around: (eq? #\012 
#\412)

You should be able to achieve what you want, but you'll have to examine 
the characters in the list by hand looking for UTF-8 sequences and only 
inserting spaces between actual characters.  Note that means that you 
would need to watch out for combining characters and other special 
things.

I do not have the time right now, but I can definitely take a stab at 
this later in the day if you would like.

-- Aaron Hill