Re: dashed \draw-line

[Thomas Morley]

2012/10/26 David Nalesnik <address@hidden>:
> Hi Kevin,
>
> On Thu, Oct 25, 2012 at 4:55 PM, Kevin Patrick Barry <address@hidden> wrote:
>> Dear LilyPond users,
>>
>> I would like the markup function \draw-line to produce a dashed line, but I
>> can't find it in the internals reference to see what overrides to use.  I
>> tried TextScript #'style, Glissando #'style and \tweak #'style.  I'm just
>> fumbling in the dark really; none of the grobs involving lines seem to be
>> it, and the spanner documentation doesn't tell me which either.  Perhaps
>> there's some way to change the line-spanner-interface?
>>
>> Thanks in advance,
>> Kevin Barry
>>
>
> I'm not aware of a markup command which draws dashed lines, and it
> appears that \draw-line is tied to a solid line. Its possible,
> however, to adapt the definition of \draw-line (found in
> scm/define-markup-commands.scm) and `make-line-stencil' (in
> scm/stencil.scm) to create a similar command.  Here you can control
> the thickness, length of the dashes (by overriding on and off).  I'm
> not sure what "phase" is for.  Anyway, hope this helps!
>
>  \version "2.17.5"
>
> #(define (make-dashed-line-stencil width startx starty endx endy on off phase)
>   (let ((xext (cons (min startx endx) (max startx endx)))
>         (yext (cons (min starty endy) (max starty endy))))
>     (ly:make-stencil
>       (list 'dashed-line
>             ; thick on off dx dy phase
>             width on off (- endx startx) (- endy starty) phase)
>       ; Since the line has rounded edges, we have to / can safely add half the
>       ; width to all coordinates!
>       (interval-widen xext (/ width 2))
>       (interval-widen yext (/ width 2)))))
>
> #(define-markup-command (draw-dashed-line layout props dest)
>   (number-pair?)
>   #:properties ((thickness 1)
>                 (on 1)
>                 (off 1)
>                 (phase 0))
>   (let ((th (* (ly:output-def-lookup layout 'line-thickness)
>                thickness))
>         (x (car dest))
>         (y (cdr dest)))
>     (make-dashed-line-stencil th 0 0 x y on off phase)))
>
> \markup \draw-dashed-line #'(11 . 0)
> \markup \override #'(off . 4) \override #'(on . 2) \override #'(thickness . 3)
>   \draw-dashed-line #'(20 . 0)
>
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Hi David,

you were faster. :)
Nevertheless, here's my slightly different coding (including your examples):

\version "2.16.0"

#(define-markup-command (draw-dashed-line layout props dest)
  (number-pair?)
  #:category graphic
  #:properties ((thickness 1)
                (on 1)
                (off 1)
                (phase 0))
  (let* ((th (* (ly:output-def-lookup layout 'line-thickness)
               thickness))
        (half-thick (/ th 2))
        (x (car dest))
        (y (cdr dest)))
    (ly:make-stencil
      (list 'dashed-line th on off x y phase)
        (interval-widen (ordered-cons 0 x) half-thick)
        (interval-widen (ordered-cons 0 y) half-thick))))

\markup \fill-line  {
        \column {
        \box \draw-dashed-line #'(-15 . 2)
        \box \draw-line #'(15 . 2)
        }
}

\markup \draw-dashed-line #'(11 . 0)
\markup
  \override #'(off . 4)
  \override #'(on . 2)
  \override #'(thickness . 3)
  \draw-dashed-line #'(20 . 0)



@Kevin
See Davids post for explanations.


Regards,
  Harm