Re: Can you determine why a grob is being typeset in scheme?

[Thomas Morley]

2015-04-21 0:21 GMT+02:00 Thomas Morley <address@hidden>:
> 2015-04-20 23:45 GMT+02:00 David Nalesnik <address@hidden>:
>> Hi Steven,
>>
>> On Mon, Apr 20, 2015 at 3:40 PM, Steven Weber <address@hidden> wrote:
>>>
>>> Since I always highlight clef changes in my music and I have access to a
>>> color printer, I thought it’d be more efficient to let Lilypond do the
>>> highlighting for me.  I wrote a handy function that places a filled-box
>>> behind the clef grob, and it works great, as long as I add it manually for
>>> every clef change.   What I really want is to add this to the Staff context
>>> so I never have to think about it again.  So I created an override function
>>> for the Staff.Clef.stencil which does the same thing as my manual function
>>> and again, it does highlight the clefs.  Unfortunately, it highlights every
>>> single clef (i.e., all the clefs at the beginning of the staves, not just
>>> the clef changes), which is overkill and defeats the purpose of highlighting
>>> things I need to pay attention to.
>>>
>>>
>>>
>>> Is there a way in scheme to say “is this grob being typeset because of an
>>> explicit command (\clef bass), or implicitly (because of a line break)”?
>>>
>>>
>>
>>
>> I can think of two ways to go about this.  Hopefully the first gives you
>> what you want, because the second will take some doing.
>>
>> Breakable items like clefs have directions attached depending on where they
>> are: -1 means end of line, 0 unbroken, and 1 beginning of line.  You can use
>> the function ly:item-break-dir like so:
>>
>> \version "2.19"
>>
>> #(define highlight
>>    (lambda (grob)
>>      (let ((ibd (ly:item-break-dir grob)))
>>        (if (= ibd 1) black green))))
>>
>> {
>>   \override Staff.Clef.color = #highlight
>>
>>   c' d' e' f'
>>   \clef bass
>>   c d e f
>>   \break
>>   c d e f
>>   \clef treble
>>   c' d' e' f'
>>   \break
>>   c' d' e' f'
>>   \clef bass
>>   \break
>>   c d e f
>> }
>>
>>
>> %%%
>>
>> One drawback here would be if you want to highlight both the cautionary clef
>> and the beginning-of-line clef at the end of the example...  To do that and
>> not catch other beginning-of-line clefs, we would have to use the other
>> method, which is to insert the override into the music expression.
>>
>> I'm going to drop out at this point :)   But, as a head start, compare the
>> results of running the following with the override left in or commented out:
>>
>> \displayMusic {
>>   c'
>>   %\override Staff.Clef.color = #highlight
>>   \clef bass
>>   c
>> }
>>
>> The extending manual discusses this sort of manipulation with respect to
>> music functions.  There are other useful commands like map-some-music which
>> crop up periodically on the lists.
>>
>> Hope this is useful--
>>
>> David
>
>
>
> Or maybe:
>
> \version "2.19.18"
>
> clef-color-engraver =
> #(lambda (context)
>  (let ((clef-props '()))
>
>   `((acknowledgers
>        (clef-interface
>         . ,(lambda (engraver grob source-engraver)
>              (let* ((clefGlyph (ly:context-property context 'clefGlyph))
>                     (clefPosition (ly:context-property context 'clefPosition))
>                     (clefTransposition
>                       (ly:context-property context 'clefTransposition 0))
>                     (new-clef-props
>                       (list clefGlyph clefPosition clefTransposition)))
>              ;(display (equal? clef-props new-clef-props))
>              (if (and (not (equal? clef-props new-clef-props))
>                       ;; to have the first clef colored as well
>                       ;; comment next line
>                       (not (null? clef-props))
>                       )
>                  (set! (ly:grob-property grob 'color) red))
>
>              (set! clef-props new-clef-props))))))))
>
> %%%%%%%%%%%%%%%
> %% EXAMPLE
> %%%%%%%%%%%%%%
>
> \layout {
>   \context {
>     \Staff
>     \consists #clef-color-engraver
>   }
> }
> <<
> {
>     \clef bass
>     R1
>     \break
>     R1
>
>     \clef alto
>     R1
>     \break
>     \clef "G"
>     R1
>     \clef "G_8"
>     R1
>     \break
>     R1
>     \break
>     R1
> }
>
> {
>     R1
>     \break
>     R1
>     R1
>     \break
>     \clef "mensural-c3"
>     R1
>     \clef "alto"
>     R1
>     \break
>     R1
>     \break
>     R1
> }
>>>
>
>
> Cheers,
>   Harm

Didn't know 'non-default myself :(

For the record, with this the engraver could be shortened to:

clef-color-engraver =
#(lambda (context)
 (let ((clef-props '()))

  `((acknowledgers
       (clef-interface
        . ,(lambda (engraver grob source-engraver)
             (if (boolean? (ly:grob-property grob 'non-default))
                 (set! (ly:grob-property grob 'color) red))))))))

Cheers,
  Harm