Re: Reading a property

[Klaus Blum]

Hi David, 

thanks for coming onboard.

First of all, I've got a function that returns a stencil:

#(define (makeDeltaSpan y-l-lower y-l-upper y-r-lower y-r-upper frame-color
fill-color stepLeft stepRight open-on-bottom open-on-top
           thick pad X-ext-param open-on-left open-on-right radius
           )
   ...etc... all the stuff needed for drawing
   )

Then, this stencil replaces the default stencil of HorizontalBracket:

genericSpan =
#(define-music-function (parser location y-l-lower y-l-upper y-r-lower
y-r-upper frame-color fill-color stepLeft stepRight open-on-bottom
open-on-top)
   (number? number? number? number? scheme? scheme? number? number? boolean?
boolean?)
   #{
     \once\override HorizontalBracket.stencil =
     $(lambda (grob)
        (let* (
                (area (ly:horizontal-bracket::print grob))
                (thick (ly:grob-property grob 'line-thickness 1))
                (pad (ly:grob-property grob 'broken-bound-padding 0))
                (radius (ly:grob-property grob 'hair-thickness 0))
                (X-ext-param (ly:stencil-extent area X))
                (open-on-left  (=  1 (ly:item-break-dir (ly:spanner-bound
grob LEFT ))))
                (open-on-right (= -1 (ly:item-break-dir (ly:spanner-bound
grob RIGHT))))
                )
          (makeDeltaSpan  y-l-lower y-l-upper y-r-lower y-r-upper
frame-color fill-color stepLeft stepRight open-on-bottom open-on-top
            thick pad X-ext-param open-on-left open-on-right radius)
          ))
     \once\override HorizontalBracket.Y-offset = #0
   #})

Although it reads out some properties, this function still has a lot of
parameters. So, I'd like to build some specialized versions.
So I could define:
\override HorizontalBracket.zigzag-width = #2
And build a new function:

ZZSpan =
#(define-music-function (parser location y-lower y-upper frame-color
fill-color)
   (number? number? scheme? scheme?)
   #{
     \genericSpan $y-lower $y-upper $y-lower $y-upper $frame-color
$fill-color 
     #2 #2  % Here I would like to read out the value from
HorizontalBracket.zigzag-width
     ##f ##f
   #})

If other functions could call \genericSpan, it would be a more elegant way.
But maybe it's easier just to copy-paste the code, as reading out properties
seems to get even more complicated.

Cheers, 
Klaus





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