-----Original Message-----
Date: Thu, 28 May 2015 07:17:42 -0500
From: David Nalesnik <address@hidden>
To: Peter Gentry <address@hidden>
Cc: lilypond-user <address@hidden>
Subject: Re: Notehead color on programmed pitch change
Message-ID:
<address@hidden>
Content-Type: text/plain; charset="utf-8"
On Thu, May 28, 2015 at 6:43 AM, Peter Gentry
<address@hidden>
wrote:
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.
You've seen
http://lilypond.org/doc/v2.18/Documentation/notation/the-tweak-command?
Any usage of \tweak in the ly file would appear in the 'tweaks
list in the music representation. Here, instead of using
\tweak in the file, we're achieving the same result by
modifying the music representation directly.
To see the music representation (basically what LilyPond does
to your ly code to make it more digestible) wrap various music
expressions in \displayMusic. For example:
\displayMusic
{
\tweak NoteHead.color #red
c''4
}
Note how the tweak is represented.
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).
Well, you'd tweak Stem. And once again, \displayMusic will
show you what is done with your ly code:
\displayMusic
{
\tweak Stem.color #blue
c''4
}
Also AFSIU
don't know this one :)
"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?
Basically.
*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.
You have to look to sources specifically devoted to Scheme.
http://www.gnu.org/software/guile/docs/docs-1.8/guile-ref/Addin
g-or-Setting-Alist-Entries.html#index-acons-1603
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 .....
The NoteHead grob will ultimately be made as a result of
processing the NoteEvent. (As will a Stem, any Dots, an
Accidental, etc.)
Various different approaches to Notehead color are evident in
the snippet
repositry agin not much detailed explanation is to be found.
http://www.lilypond.org/doc/v2.18/Documentation/learning/visibi
lity-and-color-of-objects#the-color-property
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)))))
Please format this--it's really hard to digest. With gmail,
"Paste as plain text" rather than "Paste" does the trick for
me. Maybe there's a similar option with Outlook?
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?
Please see the link above.
Hope this helps--
David