Re: SVG export - how might you add classes for all graphical objects?

[David Kastrup]

Aaron Hill <lilypond@hillvisions.com> writes:

> On 2021-06-29 9:43 am, Jean Abou Samra wrote:
>> However, this problem can be solved by writing
>> an engraver (those are the powerful tools that
>> \applyOutput uses under the hood).
>> \version "2.22.0"
>> \layout {
>>   \context {
>>     \Score
>>     \consists
>>       #(lambda (context)
>>          (make-engraver
>>            (acknowledgers
>>              ((grob-interface engraver grob source-engraver)
>>                 (set! (ly:grob-property grob 'output-attributes)
>>                       `((class . ,(grob::name grob))))))))
>>   }
>> }
>> <<
>>   { c d e f }
>>   \\
>>   { g a b c' }
>>>> 
>
> NOTE: You might want this engraver to *append* to the class attribute,
> so you can still specify classes on an individual basis:
>
> %%%%
> \version "2.22.0"
>
> SvgAddClassName =
> #(lambda (ctxt)
>   (define (add-class-name grob)
>    (let* ((attribs (ly:grob-property grob 'output-attributes '()))
>           (class (ly:assoc-get 'class attribs '()))
>           (name (grob::name grob)))
>     (set! class (if (null? class) name (format #f "~a ~a" class name)))
>     (set! attribs (assoc-set! attribs 'class class))
>     (ly:grob-set-property! grob 'output-attributes attribs)))
>   (make-engraver
>    (acknowledgers
>     ((grob-interface engraver grob source)
>      (add-class-name grob)))))

That assoc-set! looks like a stinker.  Doesn't it mess with shared data
structures?

>
> \layout { \context { \Score \consists \SvgAddClassName } }
>
> { \tweak output-attributes #'((class . foo)) b'4 }
> %%%%
>
>
> -- Aaron Hill
>
>

-- 
David Kastrup