Re: Color tweaks (edition engraver)

[David Nalesnik]

On Mon, May 4, 2015 at 10:04 PM, David Nalesnik <address@hidden> wrote:

Hi Kieren,

On Sat, May 2, 2015 at 6:29 PM, Kieren MacMillan <address@hidden> wrote:

Hi David,

> > Out of curiosity, do you get results with color-tweaks2.ly (attached somewhere above)?
> Same thing: the EE-added tweak gets executed, but doesn’t appear in the log output.
> So it doesn't get colored?

Sorry… let me be more clear. I \include-d the edition-engraver, and compiled twice: once with an \editionMod to move the [initial] Clef, and once without. The first time, the Clef moved (as expected) and was coloured (as hoped); the second time, the Clef was neither moved nor coloured (both as expected).

HOWEVER, the console output was identical in both cases: the tweak was not recorded in the output (as I thought it should have been?). 

OK, then the modifying actual grobs approach is proving to be more useful on several counts.

And it works with that editionEngraver example.

 

The attached file contains some improvements over color-tweaks2.ly.  The main difference is that it uses a simple Scheme engraver which must be \consists-ed.

\voiceTwo and the like will result in colored objects (stems for example), but I don't think there's any help for that.  Call it a feature :)

oops, forgot the custom color settings.

Anyway, this should do the trick.  Let me know how it works out.

Best,

David

%%%%%%%%%%%%%%%%%%%%%%%%%%

 

override-color = #darkred

tweak-color = #blue

%tweak-color = #override-color

#(define (remove-first symbol alist)

   "Remove the first key-value pair of association list @var{alist}

whose key matches @var{symbol}."

   (let loop ((alist alist) (result '()))

     (cond

      ((null? alist) result)

      ((eq? (caar alist) symbol)

       (append result (cdr alist)))

      (else (loop (cdr alist)

              (append result (list (car alist))))))))

#(define (grob::has-default-prop grob prop)

   "Check all-grob-descriptions to see if symbol @var{grob} has

a default setting for symbol @var{prop}.  Either return the

setting or @code{#f}."

   (let ((description (assoc-get grob all-grob-descriptions)))

     (if description

         (assoc-get 'stencil description))))

#(define (mark-tweak grob)

   "Color @var{grob} if it has been tweaked.  The color to use is stored

in the global variables @var{override-color} and @var{tweak-color}."

   (let* ((default (assoc-get (grob::name grob) all-grob-descriptions)) 

          (props (ly:grob-basic-properties grob))

          ;; Our procedure has been added to the head of grob's basic

          ;; properties.  Let's not count it as a tweak!

          (props

           (remove

            (lambda (p)

              (and (procedure? (cdr p))

                   (eq? (procedure-name (cdr p)) 'mark-tweak)))

            props))

          ;; We're using after-line-breaking to set color of stencil, but

          ;; let's preserve its last setting

          (after-line-return (assoc-get 'after-line-breaking props))

          ;; Clef.glyph doesn't appear in all-grob-descriptions, but it

          ;; is set at some point automatically.  Don't mark it unless

          ;; it genuinely is a user override.  There may be other

          ;; such grobs.

          (props

           (if (eq? (grob::name grob) 'Clef)

               (reverse (remove-first 'glyph (reverse props)))

               props))

          (diff (lset-difference eq? props default)))

     ;; Tweaks will not appear in the "basic properties" alist of our grob, but

     ;; we can find them through the music event which led to the grob.  This

     ;; is available through the stream-event which caused our grob.

     (if (null? diff)

         (let* ((cause (event-cause grob))

                (tweaks (and cause

                             (ly:music-property

                              (ly:event-property cause 'music-cause)

                              'tweaks))))

           (if (pair? tweaks)

               (set! (ly:grob-property grob 'color) tweak-color)))

         (set! (ly:grob-property grob 'color) override-color))

     

     ;; Return any default setting of after-line-breaking.

     after-line-return))

colorTweaksEngraver =

#(lambda (context)

   (make-engraver 

    (acknowledgers

     ((grob-interface engraver grob source-engraver)

      (if (grob::has-default-prop grob 'stencil)

          (set! (ly:grob-property grob 'after-line-breaking)

                (mark-tweak grob)))))))

[...your music...]

\layout {

  \context {

    \Score

    \consists \colorTweaksEngraver

  }

}