Re: id's for svg elements

[Bric]

On 10/26/2013 04:15 AM, Mike Solomon wrote:
> On Oct 26, 2013, at 10:51 AM, Bric <address@hidden> wrote:
>
> > can someone help scope out the task of adding semantically sound unique 
> > identifiers to the svg elements?
> >
> > Such that the id bears info on, at least, the staff, (maybe bar), and 
> > note/chord index (consecutive integer index, for instance)
> >
> > the "output-svg.scm" script has various routines to build the svg 
> > elements/tags/attributes, and these are implemented by other scm scripts (e.g., 
> > "round-filled-box")...
> >
> > Before I spend hours (days?) trying to figure out the precise subroutine 
> > chain/tree , perhaps someone can lead me directly to the top-level code that 
> > feeds lilypond info into these scripts? And whereby one can feed staff/movement 
> > info, along with note index down to the final svg output?
> >
> > And is this a realistic goal, I wonder?  I think even just identifying CLASS information in the 
> > "id=..." attribute might help. Just to set the stem "rect" apart from the staff line 
> > "rect", for instance, would already be an improvement; but, of course, I prefer even more 
> > specifics, as I described above.
> >
> > thanks.
> There is a grob property that is called "id" that is called far downstream 
> (right when the backends are getting the last information about the grobs before drawing 
> them).  That means that, if you create a callback for this property, you can feed it all 
> sorts of info.  The resulting SVG object will be wrapped in a group with this id.
>
> For example…
>
> \version "2.17.30"
>
> #(define (note-number grob)
>    (string-concatenate
>      (list
>        "NoteHead/"
>        (number->string
>          (ly:pitch-semitones
>            (ly:event-property (ly:grob-property grob 'cause) 'pitch))))))
>
> \relative c' {
>    \override NoteHead.id = #note-number
>    a
> }
>
> Then
>
> lilypond -dbackend=svg yourfilename.ly
>
> Then open the SVG and look for id="NoteHead/-3"
>
> Cheers,
> MS
Hi! I see it. And I can see that you're doing some sort of awesome magic 
here, but it remains a total mystery... looking at the code, and looking 
at the result, alike.

(what's a "grob property"?  I guess it's time to hit the fine manual...)

I can see that your code above generates this in the resulting *.svg file:

<g id="NoteHead/-3">
<path transform="translate(24.1197, 21.1727) scale(0.0040, -0.0040)" 
d="M217 139c57 0 112 -31 112 -94c0 -72 -55 -121 -102 -149c-35 -21 -74 
-35 -115 -35c-57 0 -112 31 -112 94c0 72 55 121 102 149c35 21 74 35 115 
35z" fill="currentColor"/>
</g>

but I have no idea why this is so, and why there's a group with only one 
member in it.  I presume you are suggesting to group the notehead, the 
stem, and maybe accidentals, and what not, under the same group and 
group id?


thanks!

(PS: how is it that you have 2.17.30, when the latest version is 2.17.29 
?  http://download.linuxaudio.org/lilypond/source/v2.17/ )