Re: Controlling hairpin length

[Thomas Morley]

2015-12-12 22:35 GMT+01:00 Thomas Morley <address@hidden>:
> 2015-12-12 17:46 GMT+01:00 David Sumbler <address@hidden>:
>> Although I quite often find myself needing to use
>>
>> \override Voice.Hairpin.minimum-length = #2
>>
>> or similar, I find that the results are unpredictable (to me!)
>>
>> Sometimes I have a very short hairpin, perhaps starting on a quaver and
>> ending on the next quaver.  In the output such a hairpin sometimes
>> appears as a short vertical line (i.e. with length=0), and a warning is
>> shown in the compiler output.
>>
>> If I change Hairpin.minimum-length I have to do it by trial and error,
>> because the result does not seem necessarily to correspond to the value
>> I have specified.  (I am assuming that the units are staff spaces.)  I'm
>> guessing that this may perhaps be something to do with having an actual
>> dynamic such as mf attached to one or both notes.
>
> It's issue 2207
> https://sourceforge.net/p/testlilyissues/issues/2207/
>
>>
>> The Internals Reference says that use of the minimum-length property
>> with a hairpin "requires an appropriate callback for the
>> springs-and-rods property".  Unfortunately I have no clear idea what
>> this means, and I haven't managed to find out yet either by searching or
>> by experimentation.  The best I have come up with so far is
>>
>> \override Hairpin.springs-and-rods = #ly:spanner::set-spacing-rods
>
> This is already the default for Hairpins (but nor for Glissando par example)
> No need to set it again in your file.
>
>>
>> This doesn't improve the output at all, but at least it doesn't produce
>> any additional error or warning!
>>
>> How can I guarantee that all hairpins will be printed with a minimum
>> length of, say, 1.5 staff spaces, and the notes spaced appropriately,
>> regardless of preceding or following dynamics?
>
> You may find the discussion at the linked issue enlightning.
>
> For now you may try the following as a workaround.
> Though, please be aware it's not tested beyond the example, your turn ;)
> Ofcorse I'll try to improve the code, if you notice issues
>
> \version "2.18.2"

Sorry, this needs a more recent version.

>
> %% a helper:
> #(define (look-up-for-parent name-symbol axis grob)
> "Return the parent of @var{grob}, specified by it's @var{name-symbol} in
> axis @var{axis} or @var{grob}, if equal to the grob named @var{name-symbol}
> already.
> If not found, look up for the next parent."
>  (let* ((parent (ly:grob-parent grob axis)))
>  (cond
>    ((not (ly:grob? parent))
>     (ly:error
>        (_"Perhaps typing error for \"~a\" or \"~a\" is not in the 
> parent-tree.")
>        name-symbol name-symbol))
>    ((equal? name-symbol (grob::name grob)) grob)
>    ((not (equal? name-symbol (grob::name parent)))
>     (look-up-for-parent name-symbol axis parent))
>    (else parent))))
>
> #(define ((hairpin-minimum-length my-minimum) grob)
>   (let* ((bound-left (ly:spanner-bound grob LEFT))
>          (bound-right (ly:spanner-bound grob RIGHT))
>          (sys (look-up-for-parent 'System Y grob))
>          (left-x-ext (ly:grob-extent bound-left sys X))
>          (right-x-ext (ly:grob-extent bound-right sys X)))
>     (ly:grob-set-property! grob 'minimum-length
>       ;; keep 'minimum-length user-settable
>       (max (ly:grob-property-data grob 'minimum-length)
>            ;; nb, this calculation is only an approximation
>            ;; should work in most cases, though
>            (+ my-minimum (abs (cdr left-x-ext)) (abs (cdr right-x-ext)))))))
>
> myHairpinMinimumLength =
> #(define-music-function (parser location minimum)(number?)
> #{
>   \override Hairpin.before-line-breaking =
>     #(hairpin-minimum-length minimum)
> #})
>
> {
>     \override Hairpin.color = #red
>     \myHairpinMinimumLength #1.5
>     \repeat unfold 8 { c4\ffff\> d\pppp\! c d \noBreak }
>     \break
>     %% overriding 'minimum-length is still possible
>     \override Hairpin.minimum-length = 20
>     \repeat unfold 8 { c4\ffff\> d\pppp\! c d \noBreak }
> }
>
>
>
> HTH,
>   Harm