Re: Custom tie vertical offsets

[Aaron Hill]

On 2020-10-09 12:20 am, Andrew Bernard wrote:
> Some time ago Harm developed custom flared tie code for me. Because
> these ties are flat and not curved, they very often come so close to
> staff lines that they can be hard to read. I can manually compensate
> for that with
>
> \once \override Tie.Y-offset = #n
>
> but this is tedious with hundreds of ties. Here's the existing code.
> Is it possible to include a vertical offset of a small amount such as
> 0.5 that intelligently takes account of the tie direction?

Firstly, you could certainly make Y-offset a procedure that applies an 
offset in the direction of the Tie:

%%%%
  \override Tie.Y-offset = #(lambda (grob)
    (* 0.5 (ly:grob-property grob 'direction)))
%%%%

That would slide all Ties half a staff space in their own direction.

Alternately, you might want to modify Harm's code to quantize the Y 
coordinate so that it always sits next to, but not on, staff lines:

%%%%
\version "2.20.0"

#(define ((flared-tie coords) grob)
  (define (scale-coords coords xex yex)
    (map (lambda (coord)
           (cons (interval-index xex (1- (* 2 (car coord))))
                 (interval-index yex (1- (* 2 (cdr coord))))))
         coords))
  (define (quantize y dir) (- (round (+ y dir)) dir))

  (if (grob::is-live? grob)
      (let* ((dir (ly:grob-property grob 'direction))
             (th (ly:staff-symbol-line-thickness grob))
             (sten (ly:tie::print grob))
             (xex (ly:stencil-extent sten X))
             (yex (ly:stencil-extent sten Y)))
        (or (< 0 dir) (set! yex (reverse-interval yex)))
        (set-cdr! yex (quantize (cdr yex) (* 3 th dir)))
        (make-connected-line
         (scale-coords coords xex yex)
         grob))
      '()))

#(define flare-tie
   (flared-tie '((0 . 0) (0.1 . 1) (0.9 . 1) (1 . 0))))
{ \override Tie.stencil = #flare-tie
  | f'2._~4 | g'2._~4 | c''2.^~4 | d''2.^~4 }
%%%%

Take note of the (* 3 th dir) in the code above.  This is the scaled 
direction factor used for the quantize procedure.  Setting this to zero 
will round the values to be exactly on the staff line.  Using (* 0.5 
dir) would result in a position exactly halfway between staff lines.  
Finally, my rationale for (* 3 th dir) is to use the thickness of the 
staff lines to help position the tie to be reasonably close to the line.


-- Aaron Hill

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