Thankyou David but how is color associated with NoteHead?
I hope these ramblings of a gnarled old scheme/Lily tyro can be of general
interest....
I'm guessing that 'tweaks is some sort of switch to open up properties of the
current music object.
In this case "pitch" is a property of 'NoteEvent and I'm guessing that color
here is just NoteHead colour not NoteStem because
NoteStem is not within the NoteEvent including 'pitch.
NoteStem color may be available in a tweak of another music object or possibly
supplied by another bit of code (engraver??).
I do not know how code a "tweak" for stem color (apart from an override in the
Lily .ly file) maybe you can't (anyway I don't want
to).
Also AFSIU "ly:music-property" extracts various elements of the current music
item (possibly contained in a deeper Lily code), and
allows user scheme to extract data from the current music object.
ly:music-set-property! does the reverse?
This part of my script kindly supplied by Thomas Morley
(if (ly:pitch? p)
(let ((new-pitch (naturalize-instrument-range p instrument)))
(ly:music-set-property! music 'pitch new-pitch)
(if (and (not (equal? p new-pitch)) (color? my-color))
(ly:music-set-property! music 'tweaks
(acons
'color my-color
(ly:music-property music 'tweaks))))))
In line 3 a pitch is written to the music event it may be the old pitch or a
new pitch.
In line 4 further action is taken if the pitch has been changed, first the
variable my-color (previously defined) is type checked
In line 5 'tweaks is inserted into the current music object.
lines 6 - 8 are a bit obscure somehow the current color is replaced by my-color
but how?
Cannot find a definition for acons but it must be a variant of cons
("consists") it occurs 8 times in snippets and once in notation
and is clearly the way to "tweak" associating the Lily 'color with the user
supplied color my-color.
Rather confusingly the format of color has many guises (x11-color 'red), (1 0
0), simply 'red (no pun intended) and notehead colour
can also be approached via a grob. The notehead grob must be somehow implied in
the (make-music .....
Various different approaches to Notehead color are evident in the snippet
repositry agin not much detailed explanation is to be
found.
upline =
#(let ((m (make-articulation "stopped")))
(set! (ly:music-property m 'tweaks)
(acons 'font-size 3
(acons 'stencil (lambda (grob)
(grob-interpret-markup
grob
(make-draw-line-markup '(0 . 1))))
(ly:music-property m 'tweaks))))
m)
\relative c' {
a'4^\upline a( c d')_\upline
}
which results in
(make-music
'RelativeOctaveMusic
'element
(make-music
'SequentialMusic
'elements
(list (make-music
'NoteEvent
'articulations
(list (make-music
'ArticulationEvent
'direction
1
'tweaks
(list (cons (quote font-size) 3)
(cons (quote stencil) #<procedure #f (grob)>))
'articulation-type
"stopped"))
'duration
(ly:make-duration 2)
'pitch
(ly:make-pitch 0 5))
(make-music
'NoteEvent
'articulations
(list (make-music
'SlurEvent
'span-direction
-1))
'duration
(ly:make-duration 2)
'pitch
(ly:make-pitch 0 5))
(make-music
'NoteEvent
'pitch
(ly:make-pitch 1 0)
'duration
(ly:make-duration 2))
(make-music
'NoteEvent
'articulations
(list (make-music
'SlurEvent
'span-direction
1)
(make-music
'ArticulationEvent
'direction
-1
'tweaks
(list (cons (quote font-size) 3)
(cons (quote stencil) #<procedure #f (grob)>))
'articulation-type
"stopped"))
'duration
(ly:make-duration 2)
'pitch
(ly:make-pitch 2 1)))))
AFAICS tweaks are not documented properly anywhere - some of the possible
tweaks are presented without detailed explanation in the
notation and snippet manuals - is there another source of information?
_____
From: David Nalesnik [mailto:david.nales...@gmail.com]
Sent: Wednesday, May 27, 2015 5:51 PM
To: Peter Gentry
Cc: lilypond-user; Thomas Morley
Subject: Re: Notehead color on programmed pitch change
On Wed, May 27, 2015 at 4:15 AM, Peter Gentry <peter.gen...@sunscales.co.uk>
wrote:
[...]
(make-music
'SequentialMusic
'elements
(list (make-music
'NoteEvent
'duration
(ly:make-duration 0)
'pitch
(ly:make-pitch 0 0))
(make-music
'NoteEvent
'tweaks
(list (list (quote color) 1.0 0.0 0.0))
[...]
Still not sure how to interpret (list (list....... But as long as Lily
does.....:)
We're simply creating a nested list:
(list (quote color) 1.0 0.0 0.0)
==>
(color 1.0 0.0 0.0)
(list (list (quote color) 1.0 0.0 0.0))
==>
((color 1.0 0.0 0.0))
By the way, (quote color) is just "longhand" for 'color
Hope that helps,
David
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