Re: What to do wanting a 4th order Bézier?

[Urs Liska]

Am 18.09.2016 um 15:49 schrieb Urs Liska:
>
> Am 18.09.2016 um 15:38 schrieb Simon Albrecht:
>> On 18.09.2016 15:15, Kieren MacMillan wrote:
>>>> And finally with a better user interface
>>> Under what circumstances would you NOT want the end of one curve to
>>> match precisely the beginning of the next one?
>>> If “none”, then I would say an even better user interface would not
>>> require typing that set of coordinates twice.
>> I thought about that too – it also makes the data structure less
>> complicated if it’s a list of seven pairs. I added the new version to
>> the LSR <http://lsr.di.unimi.it/LSR/Item?id=1045>, awaiting approval.
> There's another improvement I'm right now experimenting with: Not having
> to type the second control point of the second spline but calculating
> that mirroring it from the third one of the first spline. I noticed that
> the compound slur had a noticeable angle there, so this improvement will
> not only require one point less to type (and determine) but also ensure
> a smooth turning point.

%%%%%%%%%%%%%%%%%%%%%%%%
\version "2.19.47"
\language "deutsch"
#(define (make-cross-stencil coord)
   "Draw a cross-stencil at coord."
   (let ((thick 0.1)
         (sz 0.2))
     (stencil-with-color
      (ly:stencil-add
       (make-line-stencil
        thick
        (- (car coord) sz)
        (- (cdr coord) sz)
        (+ (car coord) sz)
        (+ (cdr coord) sz))
       (make-line-stencil
        thick
        (- (car coord) sz)
        (+ (cdr coord) sz)
        (+ (car coord) sz)
        (- (cdr coord) sz)))

      cyan)
     ))

#(define (mirror-point pt1 pt2)
   "Mirror pt2 against pt1"
   (cons
    (- (* 2 (car pt1)) (car pt2))
    (- (* 2 (cdr pt1)) (cdr pt2))))

compoundSlur =
#(define-event-function (contr-pts ann?) (list? boolean?)
   (let ((proc (lambda (grob)
                 (let*  (;; only here for reference:
                          (cps (ly:slur::calc-control-points grob))
                          (cps1 (first contr-pts))
                          (cps2 (second contr-pts))
                          (cp2-2 (mirror-point (fourth cps1) (third cps1)))
                          (cps2 `(,(fourth cps1) ,cp2-2 ,@cps2))
                          (first-spline-stil
                           (begin
                            (ly:grob-set-property! grob 'control-points
cps1)
                            (ly:slur::print grob)))
                          (second-spline-stil
                           (begin
                            (ly:grob-set-property! grob 'control-points
cps2)
                            (ly:slur::print grob)))
                          ;; annotates all new control-points
                          (crosses
                           (if ann?
                               (apply
                                ly:stencil-add
                                (map
                                 (lambda (c)
                                   (make-cross-stencil c))
                                 (append cps1 cps2)))
                               empty-stencil))
                          )
                   (display cps2)(newline)
                   ;(pretty-print cps)
                   ;; returns
                   ;;  ((0.631380973009261 . 7.545004)
                   ;;   (3.65053718406404 . 9.82511349243875)
                   ;;   (53.1972252988833 . 16.0566485774538)
                   ;;   (56.6869647738747 . 14.5951692170292))

                   (ly:stencil-add
                    first-spline-stil
                    second-spline-stil
                    crosses
                    )))))
     #{ -\tweak stencil $proc ( #}))
cptsA = #'(((0.6 . 5.8)
            (2 . 9)
            (26.0 . 5.0)
            (32 . 12))
           ((53.1 . 16.0)
            (55.5 . 12.5)))

upper = \relative {
  \key d \major
  \clef bass
  s2 r8 d,16 g h d g h
  d8 r s2.
  s4 \voiceTwo h8.(-- c16-- h2--)
}
lower = \relative {
  \key d \major
  \clef bass
  r2
  <d' h g=>~-^-\compoundSlur \cptsA ##t
  <<
    {
      <d h g>4 <c g e> <h g> \voiceOne cis
      \change Staff = upper
      \clef treble \voiceOne d e fis2)
      \fermata
    }
    \new Voice {
      \voiceTwo
      s2. <g,= e>4 \oneVoice
      <fis h,> <g e> <fis dis>2\fermata
    }
  >>
}
\score {
  <<
    \new PianoStaff <<
      \new Staff = upper \upper
      \new Staff = lower \lower
    >>
  >>
}
%%%%%%%%%%%%%%%%%%%%%%%

>
> After that I would like to suggest looking for a solution that will
> enable passing the control points as offsets against the default
> (non-compound) slur, like \shape does.
>
> Urs
>
>> Best, Simon
>>
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>
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