Re: visualize-padding

[Aaron Hill]

On 2020-01-24 9:12 am, Paolo Prete wrote:
> I'm trying to implement the work-around you suggested.
> TupletNumber doesn't cause the discussed weird space.
> However, this weird space happens as soon as I access the stencil (or 
> any
> property of it) of the TupletBracket grob
> Then, even if I get the bracket's grob with (ly:grob-object number-grob
> 'bracket), I can't access its stencil, nor its y-extent through
> this variable. Is this what you were suggesting or do I have to follow
> another method?

Alas, my workaround required that you did not need to touch 
TupletBracket's stencil property at all.  Rather, switching to 
TupletNumber might have provided you a grob that would host the 
visualization more reliably.  But if you need to access TupletBracket's 
stencil from after-line-breaking, there is no getting around the issue.

In digging more deeply, the unexpected added space looks to come from 
accessing the TupletBracket's positions property; and since stencil 
depends on positions internally, querying the stencil triggers the 
behavior.  This property is concerned with the vertical placement of the 
ends of the bracket, and its computation involves checking a number of 
associated grobs (e.g. NoteColumns and Beams).  By querying positions 
too early in the layout process, this seems to unintentionally lock in 
bad values resulting in improper spacing.  And unfortunately, 
TupletBracket's after-line-breaking procedure gets invoked *before* its 
positions property would normally be queried, so my visualization hack 
interferes with the usual timing of things.

Since TupletBracket's stencil appears to be consulted fairly late in the 
game, you probably do not need to bother with after-line-breaking at 
all.  Instead, simply replace the normal stencil procedure 
(ly:tuplet-bracket::print) with a custom one, overlaying whatever you 
need.  In 2.19, there is grob-transformer, which makes this easy:

%%%%
\version "2.19.83"

\paper {
  #(set-paper-size "a9landscape")
  top-margin = 0.75\cm line-width = 3.5\cm
  indent = 0 ragged-right = ##f tagline = ##f
}

visualize-stencil-extent-and-origin = #(define-music-function
  (grob-path) (symbol-list?)
  (define proc (grob-transformer 'stencil
    (lambda (grob orig)
      (let* ((xex (ly:stencil-extent orig X))
             (yex (ly:stencil-extent orig Y)))
        (ly:grob-set-property! grob 'layer 1000)
        (grob-interpret-markup grob #{
          \markup
          \with-dimensions-from \stencil #orig
          \overlay {
            \with-color #'(0.2 0.7 0.9)
            \override #'(style . outline)
            \override #`(thickness . 1.2)
            \whiteout
            \path #0.1 #`(
              (moveto ,(- (car xex) 1.5) ,(car yex))
              (lineto ,(+ (cdr xex) 1.5) ,(car yex))
              (moveto ,(- (car xex) 1.5) ,(cdr yex))
              (lineto ,(+ (cdr xex) 1.5) ,(cdr yex))
              (moveto ,(car xex) ,(- (car yex) 1.5))
              (lineto ,(car xex) ,(+ (cdr yex) 1.5))
              (moveto ,(cdr xex) ,(- (car yex) 1.5))
              (lineto ,(cdr xex) ,(+ (cdr yex) 1.5)))
            \with-color #'(0.9 0.4 0.2)
            \override #'(style . outline)
            \override #`(thickness . 0.9)
            \whiteout
            \path #0.1 #`(
              (moveto -1.5 -1.5) (lineto 1.5 1.5)
              (moveto -1.5 1.5) (lineto 1.5 -1.5))
            \override #'(style . outline)
            \override #`(thickness . 0.6)
            \whiteout
            \stencil #orig
          } #} )))))
  #{ \override $grob-path .stencil = #proc #})

\fixed c' {
  \visualize-stencil-extent-and-origin TupletBracket
  \tuplet 3/2 { c2 f8 bes }
}
%%%%


-- Aaron Hill

tuplet-bracket.png
Description: PNG image