Dear David, Thank you for the quick response. Overriding control-points instead of after-line-breaking made it work, although I have no idea why. I just copied the scheme code from a page in the manual. The only part of it I understand is the word grob....
I must admit I didn't know that \shape could be used on broken slurs (I love that function and use it all the time - lilypond not-infrequently draws slurs in ways I don't like). That should save me some time in the future. Thank you for the 2.16 syntax (I have never used 2.17 so I don't know it anyway). Oh, and the music is Mendelssohn! Thanks again, Kevin On 27 April 2013 13:37, David Nalesnik <david.nales...@gmail.com> wrote: > Hi Kevin, > > > On Sat, Apr 27, 2013 at 6:54 AM, Kevin Patrick Barry <barr...@tcd.ie>wrote: > >> 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 can't address the inconsistencies you describe, though... > > You can get the function to work by overriding 'control-points instead of > 'after-line-breaking. > > So, you can keep your function as is and write: > > \override PhrasingSlur #'control-points = #my-callback > > However, if altering 'control-points with the above line, it would be > cleaner to have the callback return control points: > > #(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)) > '((8.5 . 5) (11 . 7.5) (68 . 7) (70.33 . 2.75))))) > > BTW, are you aware that \shape can be used to alter broken curves as well? > You might consider using it since it will reflect changes in spacing. > > The syntax is different for 2.16 versus 2.17. For 2.16, you'd write: > > \shape PhrasingSlur '( () ((0 . 0) (0 . 2) (0 . 2) (0 . 0)) ) > > where () is equivalent to ((0 . 0) (0 . 0) (0 . 0) (0 . 0)) > indicating no change. > > You'll probably need to move the \shape override closer to the phrasing > slur, though. (Can't remember the situation with 2.16, but in 2.17 it's a > \once \override) > > HTH, > David > >
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