Re: list of thicknesses affected by changing StaffSymbol.thickness

[Paul Morris]

> On Feb 8, 2016, at 11:33 AM, Paul Morris <address@hidden> wrote:
> 
> To make things easier, I can imagine a user function that returns a list of 
> line positions based on a thickness argument (and maybe optionally a line 
> pattern list).  So for a staff with a single line at position '(2) it would 
> return '(1.9  2  2.1) or maybe just '(1.9  2.1) when given a thickness 
> argument of 0.2

\version "2.18.2"

#(define (thicker-line-positions thick pattern)
   (let ((th (/ thick 2)))
   (append-map 
    (lambda (ln) (list (- ln th) ln (+ ln th)))
    pattern)))

% #(display (thicker-line-positions 0.1 '(-4 -2 0 2 4)))
% displays:  (-4.05 -4 -3.95 -2.05 -2 -1.95 -0.05 0 0.05 1.95 2 2.05 3.95 4 
4.05)

#(define (line-positions-callback thick pattern)
   (lambda (grob) 
     (thicker-line-positions thick pattern)))


\relative {
  c'1 c c c 
}

\relative {
  \override Staff.StaffSymbol.line-positions =
  #(lambda (grob) (thicker-line-positions 0.2 '(-4 -2 0 2 4)))
  c'1 c c c 
}

\relative {
  \override Staff.StaffSymbol.line-positions =
  #(line-positions-callback 0.2 '(-4 -2 0 2 4))
  c'1 c c c 
}

%%%%%%%%%%%%%%%%%%

If we wanted to get extra fancy, we might be able to get the line-thickness 
property from the grob, and then use that to calculate things... such that when 
you entered X as a thickness input it would result in the same line thickness 
as entering X directly as a line-thickness value.  

…or there’s visual eyeballing and trial and error with the above.

Cheers,
-Paul