Hi Harm,
On Sat, Oct 22, 2011 at 11:35 AM, harm6 <[email protected]>wrote:
>
> Hi,
>
> the following function should rebuild a beam.
>
> \version "2.14.2"
>
> #(set-global-staff-size 20)
>
> #(define (test-stencil grob)
> (let* ((beam (ly:beam::print grob))
> (beam-extent-x (ly:stencil-extent beam X))
> (beam-length-x (interval-length beam-extent-x))
> (single-beam-thickness (ly:grob-property grob 'beam-thickness))
> (beam-positions (ly:grob-property grob 'positions))
> (mrkp (markup #:beam (* beam-length-x 0.97) ;; why??
> 0 ;; level Beams only!
> single-beam-thickness))
> (new-Beam (ly:stencil-in-color
> (ly:stencil-translate-axis
> (ly:stencil-translate-axis
> (grob-interpret-markup grob mrkp)
> -0.025 X) ;; why??
> (car beam-positions)
> Y)
> 1 0 0)))
>
> new-Beam))
>
> \relative c' {
> \override Beam #'layer = #-4
> \once \override Beam #'stencil = #test-stencil
> e'8 [e]
> \override Beam #'color = #green
> f8 [f]
> }
>
> But I noticed two problems:
> First I have to adjust the beam-length. (This needs to be done in addiction
> to the global-staff-size.) Seems that ly:stencil-extent gives not the exact
> value!?
> What am I missing?
>
I'm guessing that it's an issue with the markup command \beam. Looking at
the definition in define-markup-commands.scm, it seems that 'blot-diameter
isn't taken into account in the calculation of width and thickness. (Is
this intentional or a defect?) The following fixes the problem with the
beam's length and thickness, and will work when you change the staff size:
\version "2.14.2"
#(set-global-staff-size 24)
#(define (test-stencil grob)
(let* ((beam (ly:beam::print grob))
(b-d (ly:output-def-lookup (ly:grob-layout grob) 'blot-diameter))
(beam-extent-x (ly:stencil-extent beam X))
(beam-length-x (interval-length beam-extent-x))
(single-beam-thickness (ly:grob-property grob 'beam-thickness))
(beam-positions (ly:grob-property grob 'positions))
(mrkp (markup #:beam (- beam-length-x b-d)
0 ;; level Beams only!
(- single-beam-thickness b-d)))
(new-Beam (ly:stencil-in-color
(ly:stencil-translate-axis
(ly:stencil-translate-axis
(grob-interpret-markup grob mrkp)
-0.024 X) ;; why??
(car beam-positions)
Y)
1 0 0)))
new-Beam))
\relative c' {
\override Beam #'layer = #-4
\once \override Beam #'stencil = #test-stencil
e'8 [e]
\once \override Beam #'color = #red
e [e]
\override Beam #'color = #green
f8 [f]
}
> And second there's need to use ly:stencil-translate-axis to move the new
> beam a little in X-axis-direction. But why?
>
I can't figure this one out...
HTH,
David
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