Re: How to read out the slope of a beam?

[David Nalesnik]

Hi Harm,

On Sat, Oct 8, 2011 at 6:38 PM, harm6 <address@hidden> wrote:

Hi,

trying to hack Beam stencil, I need to read out the slope of the original
Beam. I thought reading out the y-extent, the x-extent and using the
quotient would do the job. But I was wrong: this quotient can't be negativ.


All the additional beams should be parallel to the originals.

How to do?

Hi Harm,

I'm not sure what the best way is to determine a beam's slope, but you might incorporate the 'position property in your function to determine whether the slope is positive or negative:

#(define (test grob)

    (let* ((beam (ly:beam::print grob))

           (dir (ly:beam::calc-direction grob))

           (beam-extent-x (ly:stencil-extent beam X))

           (beam-length-x (interval-length beam-extent-x))

           (beam-extent-y (ly:stencil-extent beam Y))

           (beam-length-y (interval-length beam-extent-y))

           (beam-thickness (* 0.48 (ly:output-def-lookup (ly:grob-layout grob) 'staff-space)))

  (beam-positions (ly:grob-property grob 'positions))

  (beam-slant (if (> (car beam-positions) (cdr beam-positions)) -1 1))

           (orig-slope (* beam-slant (/ (- beam-length-y beam-thickness) beam-length-x)))

           (markup-a (markup #:with-color red

                             #:beam beam-length-x

                                           orig-slope

                                           beam-thickness))

           )   ;; end of defs in let*

           

  (ly:stencil-add

      beam

    (ly:stencil-translate-axis

      (grob-interpret-markup grob markup-a)

      (* dir 4) Y))

      ))

 

Hope this helps!

David