Re: printKeyCancellation, a way to never show key cancellations?

[Thomas Morley]

2012/12/2 Paul Morris <address@hidden>:
>
> On Dec 2, 2012, at 3:01 PM, Keith OHara <address@hidden> wrote:
>
>> Paul Morris <paul <at> paulwmorris.com> writes:
>>
>>> For greater flexibility, would it make sense for PrintKeyCancellation to
>>> have 3 options instead of 2?
>>>  1. show key cancellations
>>>  2. hide key cancellations, except C major / A minor
>>>  3. hide all key cancellations
>>>
>> Maybe it would have, but we have gotten used to the simple true/false, which
>> does the right thing for most situations.
>>
>> Option number 3 can be had most simply with
>>
>>>  \override Staff.KeyCancellation #'stencil = ##f
>>
>> but it looks like you wrote code that restores the 'stencil for
>> anything that answers to the "key-signature-interface"
>>
>>> ((key-signature-interface engraver grob source-engraver)
>>>   (ly:grob-set-property! grob 'stencil
>>>                          (make-circle-stencil .7 .3 #f))))))
>>
>> You can stop the key cancellation by some other means as Harm suggested,
>> or change your code to stencil KeySignatures only.
>
> That makes sense.  Reading through the docs I haven't been able to figure out 
> how to do this.  If anyone has suggestions or pointers, I would appreciate it.
>
> From what I could tell the Key_engraver engraves both signatures and their 
> cancellations, and I couldn't see how (or whether) it knows which one it's 
> engraving, or how one might replicate that with custom Scheme code.  Maybe 
> one would need to hook into the code at a higher step in the order of 
> operations, where the difference between signatures and cancellations was 
> still accessible?

You can distinguish KeySignature and KeyCancellation by 'name:

\version "2.16.1"

#(define Custom_key_engraver
  (make-engraver
    (acknowledgers
      ((key-signature-interface engraver grob source-engraver)
        (let ((grob-name (lambda (x) (assq-ref (ly:grob-property x
'meta) 'name))))

        ;; For testing:
        ;; (newline)(write (grob-name grob))
        ;; (if (eq? 'KeySignature (grob-name grob))
        ;;   (ly:grob-set-property! grob 'color red)
        ;;   (ly:grob-set-property! grob 'color green))

        (if (eq? 'KeySignature (grob-name grob))
          (ly:grob-set-property! grob 'stencil (make-circle-stencil .7 .3 #f))
          (ly:grob-set-property! grob 'stencil #f)))))))

music = \relative c' {
  \time 1/4
  \key a \major
  d4
  \key f \major
  d
  \key a \major
  d
  \key f \major
  d
  \key a \major
  d
  \break
  \key c \major
  d
  \key a \major
  d
  \key c \major
  d
}

\score
{
  <<
  \new Staff { \music }
  \new Staff \with { \consists \Custom_key_engraver }
  { \music }
  >>
  \layout { }
}


HTH,
  Harm