Re: Translating stencils

[Thomas Morley]

Am Mo., 23. Sept. 2019 um 18:04 Uhr schrieb Michael Käppler <address@hidden>:
>
> Hi all,
> I'm trying to understand the way one can translate / stack stencils in
> LilyPond.
> Consider the following code:
>
> #(define-markup-command (draw-line-mod layout props startpos endpos)
>     (number-pair? number-pair?)
>     #:properties ((thickness 1))
>
>    (let ((th (* (ly:output-def-lookup layout 'line-thickness)
>                 thickness))
>          (startx (car startpos))
>          (starty (cdr startpos))
>          (endx (car endpos))
>          (endy (cdr endpos)))
>      (make-line-stencil th startx starty endx endy)))
>
> #(define hlineone (markup #:draw-line-mod '(0 . 0) '(10 . 0)))
> #(define hlinetwo (markup #:draw-line-mod '(0 . 10) '(10 . 10)))
>
> #(define vlineone (markup #:draw-line-mod '(0 . 0) '(0 . 10)))
> #(define vlinetwo (markup #:draw-line-mod '(10 . 0) '(10 . 10)))
>
> \markup \hlineone
> % \markup \hlinetwo
> % \markup \vlineone
> % \markup \vlinetwo
>
> The ordinary draw-line markup function calls (make-line-stencil) with
> startx/starty 0 0.
> So I wrote the custom draw-line-mod function to figure out what happens
> when I set the startx / starty to different values.
> What I understand is that these values do not specify "absolute
> coordinates" somewhere on the paper, but are somehow relative
> to each other. But how exactly?
>
> \markup \hlinetwo gives a line positioned exactly like \hlineone, though
> the stencil has different starty.
> \markup \vlinetwo, however,  gives a line starting at a different
> vertical position than \vlineone.
>
> Eventually I want to draw a kind of grid with horizontal and vertical
> lines, placing little "scores" in them.
> Attached is an example of what I want to achieve. But I do not want a
> quick solution, instead I would be glad to understand
> the stencil positioning better than now.
>
> Kind regards,
> Michael

If I understand correctly:
If you place a bunch of stencils on a page, then lilyponds
spacing-engine will drop in and white space may be disregarded. See:

\paper { markup-markup-spacing.padding = 5 }

\markup \hlineone
\markup \hlinetwo
\markup \vlineone
\markup \vlinetwo

And compare with:

\markup {
  \hlineone
  \hlinetwo
  \vlineone
  \vlinetwo
}

With the latter you can observe all the different settings (relative
to the previous stencil)

For your final goal, checkout the table-markup-list-command.
No lines implemented there, but probably a starting point.

Cheers,
  Harm