Hi, On Fri, Mar 20, 2015 at 7:14 AM, Paul Morris <p...@paulwmorris.com> wrote:
> There's a snippet in the lsr for accessing grobs "laterally" from another > grob's callback: > http://lsr.di.unimi.it/LSR/Item?id=621 > > ...like accessing the stem grob from a note head grob. There's also one > on showing "grob ancestry" that's helpful for this kind of thing. > > This is a helpful snippet. If you look at the various interface pages, under "Internal Properties" in the Internals Reference, you'll find other grobs (single grobs or multiple grobs stored in a "grob-array") that your grob stores pointers to, meaning that you have easy access to the other object(s). The grob NoteHead has "rhythmic-head-interface" (see bottom of page at http://lilypond.org/doc/v2.19/Documentation/internals/notehead). Under the Internals page for that interface http://lilypond.org/doc/v2.19/Documentation/internals/rhythmic_002dhead_002dinterface we find: Internal properties: dot (graphical (layout) object) A reference to a Dots object. stem (graphical (layout) object) A pointer to a Stem object. With ly:grob-object, we can get at either a Dot or a Stem. So, with your function you could write: #(define alt-notehead (lambda (grob) (let ((stem (ly:grob-object grob 'stem))) (if (ly:grob? stem) ;; perhaps unnecessary, but let's be safe (if (eq? (ly:grob-property stem 'direction) DOWN) (grob-interpret-markup grob stil) (grob-interpret-markup grob newstil)))))) Finding the path from one object to another is usually just a matter of trial-and-error, following this path, following that path, until you reach the pot of gold. HTH, David
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