Peculiar issue with something I copied from advanced tweaks

[Kevin Patrick Barry]

Dear LilyPond users,

I need help with a strange problem I have encountered.  I wanted to edit the control points of a phrasing slur that has a line break.  I found a page about this in the lilypond manual, from which I adapted the following code:

#(define (my-callback grob)

(let* (

;; have we been split?

(orig (ly:grob-original grob))

;; if yes, get the split pieces (our siblings)

(siblings (if (ly:grob? orig)

(ly:spanner-broken-into orig)

'())))

(if (and (>= (length siblings) 2)

(eq? (car (last-pair siblings)) grob))

(ly:grob-set-property! grob 'control-points '((8.5 . 5) (11 . 7.5) (68 . 7) (70.33 . 2.75))))))

When I added an \override PhrasingSlur #'after-line-breaking = #my-callback everything looked OK in Frescobaldi (2.08, running on Ubuntu 13.04), but when I engrave the file from the command line it engraves it without the override (the phrasing slur appears as it did before). I made sure to save changes. Even if I copy the command line from Frescobaldi it will not engrave correctly. Both Frescobaldi and the command line state that they are using 2.16.2 (which is the only version installed anyway).

I haven't been able to reproduce the issue in a tiny example, but I have noticed that the override I used (I don't understand the scheme code) is very temperamental. For example I can only get it to work when the Bar number engraver is removed. In another test I was able to break it simply by adding the Horizontal bracket engraver to the voice context: I use lots of style files in my work (and the horizontal bracket engraver is included in them) and when preparing a stand-alone version of the file to attach I removed the \include and added the engraver explicity which immediately caused the override to stop working.

If anyone has the patience to look into this I have attached a file which reproduces the problem (I'm sorry I couldn't pare it down; there must be some weird interactions that I don't understand going on). I had to leave the horizontal bracket engraver out.

I appreciate any help,

Kevin

test.ly
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