+++ /dev/null
-@c -*- coding: utf-8; mode: texinfo; -*-
-@c This file is part of lilypond.tely
-@ignore
- Translation of GIT committish: FILL-IN-HEAD-COMMITTISH
-
- When revising a translation, copy the HEAD committish of the
- version that you are working on. See TRANSLATION for details.
-@end ignore
-
-@c \version "2.12.0"
-
-@node Interfaces for programmers
-@chapter Interfaces for programmers
-
-Advanced tweaks may be performed by using Scheme. If you are
-not familiar with Scheme, you may wish to read our
-@rlearning{Scheme tutorial}.
-
-@menu
-* Music functions::
-* Programmer interfaces::
-* Building complicated functions::
-* Markup programmer interface::
-* Contexts for programmers::
-* Scheme procedures as properties::
-* Using Scheme code instead of \tweak::
-* Difficult tweaks::
-@end menu
-
-
-@node Music functions
-@section Music functions
-
-This section discusses how to create music functions within LilyPond.
-
-@menu
-* Overview of music functions::
-* Simple substitution functions::
-* Paired substitution functions::
-* Mathematics in functions::
-* Void functions::
-* Functions without arguments::
-* Overview of available music functions::
-@end menu
-
-@node Overview of music functions
-@subsection Overview of music functions
-
-Making a function which substitutes a variable into LilyPond
-code is easy. The general form of these functions is
-
-@example
-function =
-#(define-music-function (parser location @var{var1} @var{var2}...@var{vari}... )
- (@var{var1-type?} @var{var2-type?}...@var{vari-type?}...)
- #@{
- @emph{...music...}
- #@})
-@end example
-
-@noindent
-where
-
-@multitable @columnfractions .33 .66
-@item @var{vari} @tab @var{i}th variable
-@item @var{vari-type?} @tab type of @var{i}th variable
-@item @var{...music...} @tab normal LilyPond input, using
- variables as @code{#$var1}, etc.
-@end multitable
-
-There following input types may be used as variables
-in a music function. This list is not exhaustive; see
-other documentation specifically about Scheme for more
-variable types.
-
-@multitable @columnfractions .33 .66
-@headitem Input type @tab @var{vari-type?} notation
-@item Integer @tab @code{integer?}
-@item Float (decimal number) @tab @code{number?}
-@item Text string @tab @code{string?}
-@item Markup @tab @code{markup?}
-@item Music expression @tab @code{ly:music?}
-@item A pair of variables @tab @code{pair?}
-@end multitable
-
-The @code{parser} and @code{location} arguments are mandatory,
-and are used in some advanced situations. The @code{parser}
-argument is used to gain access to the value of another LilyPond
-variable. The @code{location} argument
-is used to set the @q{origin} of the music expression that is built
-by the music function, so that in case of a syntax error LilyPond
-can tell the user an appropriate place to look in the input file.
-
-
-@node Simple substitution functions
-@subsection Simple substitution functions
-
-Here is a simple example,
-
-@lilypond[quote,verbatim,ragged-right]
-padText = #(define-music-function (parser location padding) (number?)
- #{
- \once \override TextScript #'padding = #$padding
- #})
-
-\relative c''' {
- c4^"piu mosso" b a b
- \padText #1.8
- c4^"piu mosso" d e f
- \padText #2.6
- c4^"piu mosso" fis a g
-}
-@end lilypond
-
-Music expressions may be substituted as well,
-
-@lilypond[quote,verbatim,ragged-right]
-custosNote = #(define-music-function (parser location note)
- (ly:music?)
- #{
- \once \override Voice.NoteHead #'stencil =
- #ly:text-interface::print
- \once \override Voice.NoteHead #'text =
- \markup \musicglyph #"custodes.mensural.u0"
- \once \override Voice.Stem #'stencil = ##f
- $note
- #})
-
-{ c' d' e' f' \custosNote g' }
-@end lilypond
-
-Multiple variables may be used,
-
-@lilypond[quote,verbatim,ragged-right]
-tempoMark = #(define-music-function (parser location padding marktext)
- (number? string?)
-#{
- \once \override Score . RehearsalMark #'padding = $padding
- \once \override Score . RehearsalMark #'extra-spacing-width = #'(+inf.0 . -inf.0)
- \mark \markup { \bold $marktext }
-#})
-
-\relative c'' {
-c2 e
-\tempoMark #3.0 #"Allegro"
-g c
-}
-@end lilypond
-
-
-@node Paired substitution functions
-@subsection Paired substitution functions
-
-Some @code{\override} commands require a pair of numbers
-(called a @code{cons cell} in Scheme). To pass these numbers
-into a function, either use a @code{pair?} variable, or
-insert the @code{cons} into the music function.
-
-@quotation
-@example
-manualBeam =
-#(define-music-function (parser location beg-end)
- (pair?)
-#@{
- \once \override Beam #'positions = #$beg-end
-#@})
-
-\relative @{
- \manualBeam #'(3 . 6) c8 d e f
-@}
-@end example
-@end quotation
-
-@noindent
-or
-
-@lilypond[quote,verbatim,ragged-right]
-manualBeam =
-#(define-music-function (parser location beg end)
- (number? number?)
-#{
- \once \override Beam #'positions = #(cons $beg $end)
-#})
-
-\relative {
- \manualBeam #3 #6 c8 d e f
-}
-@end lilypond
-
-
-@node Mathematics in functions
-@subsection Mathematics in functions
-
-Music functions can involve Scheme programming in
-addition to simple substitution,
-
-@lilypond[quote,verbatim,ragged-right]
-AltOn = #(define-music-function (parser location mag) (number?)
- #{ \override Stem #'length = #$(* 7.0 mag)
- \override NoteHead #'font-size =
- #$(inexact->exact (* (/ 6.0 (log 2.0)) (log mag))) #})
-
-AltOff = {
- \revert Stem #'length
- \revert NoteHead #'font-size
-}
-
-{ c'2 \AltOn #0.5 c'4 c'
- \AltOn #1.5 c' c' \AltOff c'2 }
-@end lilypond
-
-@noindent
-This example may be rewritten to pass in music expressions,
-
-@lilypond[quote,verbatim,ragged-right]
-withAlt = #(define-music-function (parser location mag music) (number? ly:music?)
- #{ \override Stem #'length = #$(* 7.0 mag)
- \override NoteHead #'font-size =
- #$(inexact->exact (* (/ 6.0 (log 2.0)) (log mag)))
- $music
- \revert Stem #'length
- \revert NoteHead #'font-size #})
-
-{ c'2 \withAlt #0.5 {c'4 c'}
- \withAlt #1.5 {c' c'} c'2 }
-@end lilypond
-
-@node Void functions
-@subsection Void functions
-
-A music function must return a music expression, but sometimes we
-may want to have a function which does not involve music (such as
-turning off Point and Click). To do this, we return a @code{void}
-music expression.
-
-That is why the form
-that is returned is the @code{(make-music ...)}. With the
-@code{'void} property set to @code{#t}, the parser is told to
-actually disregard this returned music
-expression. Thus the important part of the void music function is the
-processing done by the function, not the music expression that is
-returned.
-
-@example
-noPointAndClick =
-#(define-music-function (parser location) ()
- (ly:set-option 'point-and-click #f)
- (make-music 'SequentialMusic 'void #t))
-...
-\noPointAndClick % disable point and click
-@end example
-
-
-@node Functions without arguments
-@subsection Functions without arguments
-
-In most cases a function without arguments should be written
-with an variable,
-
-@example
-dolce = \markup@{ \italic \bold dolce @}
-@end example
-
-However, in rare cases it may be useful to create a music function
-without arguments,
-
-@example
-displayBarNum =
-#(define-music-function (parser location) ()
- (if (eq? #t (ly:get-option 'display-bar-numbers))
- #@{ \once \override Score.BarNumber #'break-visibility = ##f #@}
- #@{#@}))
-@end example
-
-To actually display bar numbers where this function is called,
-invoke @command{lilypond} with
-
-@example
-lilypond -d display-bar-numbers FILENAME.ly
-@end example
-
-
-@node Overview of available music functions
-@subsection Overview of available music functions
-
-@c fixme ; this should be move somewhere else?
-The following commands are music functions
-
-@include identifiers.tely
-
-
-
-@node Programmer interfaces
-@section Programmer interfaces
-
-This section contains information about mixing LilyPond
-and Scheme.
-
-@menu
-* Input variables and Scheme::
-* Internal music representation::
-@end menu
-
-
-@node Input variables and Scheme
-@subsection Input variables and Scheme
-
-The input format supports the notion of variables: in the following
-example, a music expression is assigned to a variable with the name
-@code{traLaLa}.
-
-@example
-traLaLa = @{ c'4 d'4 @}
-@end example
-
-@noindent
-
-There is also a form of scoping: in the following example, the
-@code{\layout} block also contains a @code{traLaLa} variable, which is
-independent of the outer @code{\traLaLa}.
-@example
-traLaLa = @{ c'4 d'4 @}
-\layout @{ traLaLa = 1.0 @}
-@end example
-@c
-In effect, each input file is a scope, and all @code{\header},
-@code{\midi}, and @code{\layout} blocks are scopes nested inside that
-toplevel scope.
-
-Both variables and scoping are implemented in the GUILE module system.
-An anonymous Scheme module is attached to each scope. An assignment of
-the form
-@example
-traLaLa = @{ c'4 d'4 @}
-@end example
-
-@noindent
-is internally converted to a Scheme definition
-@example
-(define traLaLa @var{Scheme value of `@code{... }'})
-@end example
-
-This means that input variables and Scheme variables may be freely
-mixed. In the following example, a music fragment is stored in the
-variable @code{traLaLa}, and duplicated using Scheme. The result is
-imported in a @code{\score} block by means of a second variable
-@code{twice}:
-
-@lilypond[verbatim]
-traLaLa = { c'4 d'4 }
-
-%% dummy action to deal with parser lookahead
-#(display "this needs to be here, sorry!")
-
-#(define newLa (map ly:music-deep-copy
- (list traLaLa traLaLa)))
-#(define twice
- (make-sequential-music newLa))
-
-{ \twice }
-@end lilypond
-
-@c Due to parser lookahead
-
-In this example, the assignment happens after parser has verified that
-nothing interesting happens after @code{traLaLa = @{ ... @}}. Without
-the dummy statement in the above example, the @code{newLa} definition
-is executed before @code{traLaLa} is defined, leading to a syntax
-error.
-
-The above example shows how to @q{export} music expressions from the
-input to the Scheme interpreter. The opposite is also possible. By
-wrapping a Scheme value in the function @code{ly:export}, a Scheme
-value is interpreted as if it were entered in LilyPond syntax.
-Instead of defining @code{\twice}, the example above could also have
-been written as
-
-@example
-...
-@{ #(ly:export (make-sequential-music (list newLa))) @}
-@end example
-
-Scheme code is evaluated as soon as the parser encounters it. To
-define some Scheme code in a macro (to be called later), use
-@ref{Void functions}, or
-
-@example
-#(define (nopc)
- (ly:set-option 'point-and-click #f))
-
-...
-#(nopc)
-@{ c'4 @}
-@end example
-
-
-@knownissues
-
-Mixing Scheme and LilyPond variables is not possible with the
-@code{--safe} option.
-
-
-@node Internal music representation
-@subsection Internal music representation
-
-When a music expression is parsed, it is converted into a set of
-Scheme music objects. The defining property of a music object is that
-it takes up time. Time is a rational number that measures the length
-of a piece of music in whole notes.
-
-A music object has three kinds of types:
-@itemize
-@item
-music name: Each music expression has a name. For example, a note
-leads to a @rinternals{NoteEvent}, and @code{\simultaneous} leads to
-a @rinternals{SimultaneousMusic}. A list of all expressions
-available is in the Internals Reference manual, under
-@rinternals{Music expressions}.
-
-@item
-@q{type} or interface: Each music name has several @q{types} or
-interfaces, for example, a note is an @code{event}, but it is also a
-@code{note-event}, a @code{rhythmic-event}, and a
-@code{melodic-event}. All classes of music are listed in the
-Internals Reference, under
-@rinternals{Music classes}.
-
-@item
-C++ object: Each music object is represented by an object of the C++
-class @code{Music}.
-@end itemize
-
-The actual information of a music expression is stored in properties.
-For example, a @rinternals{NoteEvent} has @code{pitch} and
-@code{duration} properties that store the pitch and duration of that
-note. A list of all properties available is in the internals manual,
-under @rinternals{Music properties}.
-
-A compound music expression is a music object that contains other
-music objects in its properties. A list of objects can be stored in
-the @code{elements} property of a music object, or a single @q{child}
-music object in the @code{element} property. For example,
-@rinternals{SequentialMusic} has its children in @code{elements},
-and @rinternals{GraceMusic} has its single argument in
-@code{element}. The body of a repeat is stored in the @code{element}
-property of @rinternals{RepeatedMusic}, and the alternatives in
-@code{elements}.
-
-
-
-@node Building complicated functions
-@section Building complicated functions
-
-This section explains how to gather the information necessary
-to create complicated music functions.
-
-@menu
-* Displaying music expressions::
-* Music properties::
-* Doubling a note with slurs (example)::
-* Adding articulation to notes (example)::
-@end menu
-
-
-@node Displaying music expressions
-@subsection Displaying music expressions
-
-@cindex internal storage
-@funindex \displayMusic
-
-When writing a music function it is often instructive to inspect how
-a music expression is stored internally. This can be done with the
-music function @code{\displayMusic}
-
-@example
-@{
- \displayMusic @{ c'4\f @}
-@}
-@end example
-
-@noindent
-will display
-
-@example
-(make-music
- 'SequentialMusic
- 'elements
- (list (make-music
- 'EventChord
- 'elements
- (list (make-music
- 'NoteEvent
- 'duration
- (ly:make-duration 2 0 1 1)
- 'pitch
- (ly:make-pitch 0 0 0))
- (make-music
- 'AbsoluteDynamicEvent
- 'text
- "f")))))
-@end example
-
-By default, LilyPond will print these messages to the console along
-with all the other messages. To split up these messages and save
-the results of @code{\display@{STUFF@}}, redirect the output to
-a file.
-
-@example
-lilypond file.ly >display.txt
-@end example
-
-With a bit of reformatting, the above information is
-easier to read,
-
-@example
-(make-music 'SequentialMusic
- 'elements (list (make-music 'EventChord
- 'elements (list (make-music 'NoteEvent
- 'duration (ly:make-duration 2 0 1 1)
- 'pitch (ly:make-pitch 0 0 0))
- (make-music 'AbsoluteDynamicEvent
- 'text "f")))))
-@end example
-
-A @code{@{ ... @}} music sequence has the name @code{SequentialMusic},
-and its inner expressions are stored as a list in its @code{'elements}
-property. A note is represented as an @code{EventChord} expression,
-containing a @code{NoteEvent} object (storing the duration and
-pitch properties) and any extra information (in this case, an
-@code{AbsoluteDynamicEvent} with a @code{"f"} text property.
-
-
-@node Music properties
-@subsection Music properties
-
-The @code{NoteEvent} object is the first object of the
-@code{'elements} property of @code{someNote}.
-
-@example
-someNote = c'
-\displayMusic \someNote
-===>
-(make-music
- 'EventChord
- 'elements
- (list (make-music
- 'NoteEvent
- 'duration
- (ly:make-duration 2 0 1 1)
- 'pitch
- (ly:make-pitch 0 0 0))))
-@end example
-
-The @code{display-scheme-music} function is the function used by
-@code{\displayMusic} to display the Scheme representation of a music
-expression.
-
-@example
-#(display-scheme-music (first (ly:music-property someNote 'elements)))
-===>
-(make-music
- 'NoteEvent
- 'duration
- (ly:make-duration 2 0 1 1)
- 'pitch
- (ly:make-pitch 0 0 0))
-@end example
-
-Then the note pitch is accessed through the @code{'pitch} property
-of the @code{NoteEvent} object,
-
-@example
-#(display-scheme-music
- (ly:music-property (first (ly:music-property someNote 'elements))
- 'pitch))
-===>
-(ly:make-pitch 0 0 0)
-@end example
-
-The note pitch can be changed by setting this 'pitch property,
-
-@funindex \displayLilyMusic
-
-@example
-#(set! (ly:music-property (first (ly:music-property someNote 'elements))
- 'pitch)
- (ly:make-pitch 0 1 0)) ;; set the pitch to d'.
-\displayLilyMusic \someNote
-===>
-d'
-@end example
-
-
-@node Doubling a note with slurs (example)
-@subsection Doubling a note with slurs (example)
-
-Suppose we want to create a function which translates
-input like @code{a} into @code{a( a)}. We begin
-by examining the internal representation of the music
-we want to end up with.
-
-@example
-\displayMusic@{ a'( a') @}
-===>
-(make-music
- 'SequentialMusic
- 'elements
- (list (make-music
- 'EventChord
- 'elements
- (list (make-music
- 'NoteEvent
- 'duration
- (ly:make-duration 2 0 1 1)
- 'pitch
- (ly:make-pitch 0 5 0))
- (make-music
- 'SlurEvent
- 'span-direction
- -1)))
- (make-music
- 'EventChord
- 'elements
- (list (make-music
- 'NoteEvent
- 'duration
- (ly:make-duration 2 0 1 1)
- 'pitch
- (ly:make-pitch 0 5 0))
- (make-music
- 'SlurEvent
- 'span-direction
- 1)))))
-@end example
-
-The bad news is that the @code{SlurEvent} expressions
-must be added @q{inside} the note (or more precisely,
-inside the @code{EventChord} expression).
-
-Now we examine the input,
-
-@example
-(make-music
- 'SequentialMusic
- 'elements
- (list (make-music
- 'EventChord
- 'elements
- (list (make-music
- 'NoteEvent
- 'duration
- (ly:make-duration 2 0 1 1)
- 'pitch
- (ly:make-pitch 0 5 0))))))
-@end example
-
-So in our function, we need to clone this expression (so that we
-have two notes to build the sequence), add @code{SlurEvents} to the
-@code{'elements} property of each one, and finally make a
-@code{SequentialMusic} with the two @code{EventChords}.
-
-@example
-doubleSlur = #(define-music-function (parser location note) (ly:music?)
- "Return: @{ note ( note ) @}.
- `note' is supposed to be an EventChord."
- (let ((note2 (ly:music-deep-copy note)))
- (set! (ly:music-property note 'elements)
- (cons (make-music 'SlurEvent 'span-direction -1)
- (ly:music-property note 'elements)))
- (set! (ly:music-property note2 'elements)
- (cons (make-music 'SlurEvent 'span-direction 1)
- (ly:music-property note2 'elements)))
- (make-music 'SequentialMusic 'elements (list note note2))))
-@end example
-
-
-@node Adding articulation to notes (example)
-@subsection Adding articulation to notes (example)
-
-The easy way to add articulation to notes is to merge two music
-expressions into one context, as explained in
-@ref{Creating contexts}. However, suppose that we want to write
-a music function which does this.
-
-A @code{$variable} inside the @code{#@{...#@}} notation is like
-using a regular @code{\variable} in classical LilyPond
-notation. We know that
-
-@example
-@{ \music -. -> @}
-@end example
-
-@noindent
-will not work in LilyPond. We could avoid this problem by attaching
-the articulation to a fake note,
-
-@example
-@{ << \music s1*0-.-> @}
-@end example
-
-@noindent
-but for the sake of this example, we will learn how to do this in
-Scheme. We begin by examining our input and desired output,
-
-@example
-% input
-\displayMusic c4
-===>
-(make-music
- 'EventChord
- 'elements
- (list (make-music
- 'NoteEvent
- 'duration
- (ly:make-duration 2 0 1 1)
- 'pitch
- (ly:make-pitch -1 0 0))))
-=====
-% desired output
-\displayMusic c4->
-===>
-(make-music
- 'EventChord
- 'elements
- (list (make-music
- 'NoteEvent
- 'duration
- (ly:make-duration 2 0 1 1)
- 'pitch
- (ly:make-pitch -1 0 0))
- (make-music
- 'ArticulationEvent
- 'articulation-type
- "marcato")))
-@end example
-
-We see that a note (@code{c4}) is represented as an @code{EventChord}
-expression, with a @code{NoteEvent} expression in its elements list. To
-add a marcato articulation, an @code{ArticulationEvent} expression must
-be added to the elements property of the @code{EventChord}
-expression.
-
-To build this function, we begin with
-
-@example
-(define (add-marcato event-chord)
- "Add a marcato ArticulationEvent to the elements of `event-chord',
- which is supposed to be an EventChord expression."
- (let ((result-event-chord (ly:music-deep-copy event-chord)))
- (set! (ly:music-property result-event-chord 'elements)
- (cons (make-music 'ArticulationEvent
- 'articulation-type "marcato")
- (ly:music-property result-event-chord 'elements)))
- result-event-chord))
-@end example
-
-The first line is the way to define a function in Scheme: the function
-name is @code{add-marcato}, and has one variable called
-@code{event-chord}. In Scheme, the type of variable is often clear
-from its name. (this is good practice in other programming languages,
-too!)
-
-@example
-"Add a marcato..."
-@end example
-
-@noindent
-is a description of what the function does. This is not strictly
-necessary, but just like clear variable names, it is good practice.
-
-@example
-(let ((result-event-chord (ly:music-deep-copy event-chord)))
-@end example
-
-@code{let} is used to declare local variables. Here we use one local
-variable, named @code{result-event-chord}, to which we give the value
-@code{(ly:music-deep-copy event-chord)}. @code{ly:music-deep-copy} is
-a function specific to LilyPond, like all functions prefixed by
-@code{ly:}. It is use to make a copy of a music
-expression. Here we copy @code{event-chord} (the parameter of the
-function). Recall that our purpose is to add a marcato to an
-@code{EventChord} expression. It is better to not modify the
-@code{EventChord} which was given as an argument, because it may be
-used elsewhere.
-
-Now we have a @code{result-event-chord}, which is a
-@code{NoteEventChord} expression and is a copy of @code{event-chord}. We
-add the marcato to its elements list property.
-
-@example
-(set! place new-value)
-@end example
-
-Here, what we want to set (the @q{place}) is the @q{elements} property of
-@code{result-event-chord} expression.
-
-@example
-(ly:music-property result-event-chord 'elements)
-@end example
-
-@code{ly:music-property} is the function used to access music properties
-(the @code{'elements}, @code{'duration}, @code{'pitch}, etc, that we
-see in the @code{\displayMusic} output above). The new value is the
-former elements property, with an extra item: the
-@code{ArticulationEvent} expression, which we copy from the
-@code{\displayMusic} output,
-
-@example
-(cons (make-music 'ArticulationEvent
- 'articulation-type "marcato")
- (ly:music-property result-event-chord 'elements))
-@end example
-
-@code{cons} is used to add an element to a list without modifying the
-original list. This is what we
-want: the same list as before, plus the new @code{ArticulationEvent}
-expression. The order inside the elements property is not important here.
-
-Finally, once we have added the marcato articulation to its @code{elements}
-property, we can return @code{result-event-chord}, hence the last line of
-the function.
-
-Now we transform the @code{add-marcato} function into a music
-function,
-
-@example
-addMarcato = #(define-music-function (parser location event-chord)
- (ly:music?)
- "Add a marcato ArticulationEvent to the elements of `event-chord',
- which is supposed to be an EventChord expression."
- (let ((result-event-chord (ly:music-deep-copy event-chord)))
- (set! (ly:music-property result-event-chord 'elements)
- (cons (make-music 'ArticulationEvent
- 'articulation-type "marcato")
- (ly:music-property result-event-chord 'elements)))
- result-event-chord))
-@end example
-
-We may verify that this music function works correctly,
-
-@example
-\displayMusic \addMarcato c4
-@end example
-
-
-@node Markup programmer interface
-@section Markup programmer interface
-
-Markups are implemented as special Scheme functions which produce a
-Stencil object given a number of arguments.
-
-@menu
-* Markup construction in Scheme::
-* How markups work internally::
-* New markup command definition::
-* New markup list command definition::
-@end menu
-
-
-@node Markup construction in Scheme
-@subsection Markup construction in Scheme
-
-@cindex defining markup commands
-
-The @code{markup} macro builds markup expressions in Scheme while
-providing a LilyPond-like syntax. For example,
-@example
-(markup #:column (#:line (#:bold #:italic "hello" #:raise 0.4 "world")
- #:larger #:line ("foo" "bar" "baz")))
-@end example
-
-@noindent
-is equivalent to:
-@example
-\markup \column @{ \line @{ \bold \italic "hello" \raise #0.4 "world" @}
- \larger \line @{ foo bar baz @} @}
-@end example
-
-@noindent
-This example demonstrates the main translation rules between regular
-LilyPond markup syntax and Scheme markup syntax.
-
-@quotation
-@multitable @columnfractions .3 .3
-@item @b{LilyPond} @tab @b{Scheme}
-@item @code{\markup markup1} @tab @code{(markup markup1)}
-@item @code{\markup @{ markup1 markup2 ... @}} @tab
- @code{(markup markup1 markup2 ... )}
-@item @code{\command} @tab @code{#:command}
-@item @code{\variable} @tab @code{variable}
-@item @code{\center-column @{ ... @}} @tab @code{#:center-column ( ... )}
-@item @code{string} @tab @code{"string"}
-@item @code{#scheme-arg} @tab @code{scheme-arg}
-@end multitable
-@end quotation
-
-The whole Scheme language is accessible inside the
-@code{markup} macro. For example, You may use function calls inside
-@code{markup} in order to manipulate character strings. This is
-useful when defining new markup commands (see
-@ref{New markup command definition}).
-
-
-@knownissues
-
-The markup-list argument of commands such as @code{#:line},
-@code{#:center}, and @code{#:column} cannot be a variable or
-the result of a function call.
-
-@lisp
-(markup #:line (function-that-returns-markups))
-@end lisp
-
-@noindent
-is invalid. One should use the @code{make-line-markup},
-@code{make-center-markup}, or @code{make-column-markup} functions
-instead,
-
-@lisp
-(markup (make-line-markup (function-that-returns-markups)))
-@end lisp
-
-
-@node How markups work internally
-@subsection How markups work internally
-
-In a markup like
-
-@example
-\raise #0.5 "text example"
-@end example
-
-@noindent
-@code{\raise} is actually represented by the @code{raise-markup}
-function. The markup expression is stored as
-
-@example
-(list raise-markup 0.5 (list simple-markup "text example"))
-@end example
-
-When the markup is converted to printable objects (Stencils), the
-@code{raise-markup} function is called as
-
-@example
-(apply raise-markup
- @var{\layout object}
- @var{list of property alists}
- 0.5
- @var{the "text example" markup})
-@end example
-
-The @code{raise-markup} function first creates the stencil for the
-@code{text example} string, and then it raises that Stencil by 0.5
-staff space. This is a rather simple example; more complex examples
-are in the rest
-of this section, and in @file{scm/@/define@/-markup@/-commands@/.scm}.
-
-
-@node New markup command definition
-@subsection New markup command definition
-
-New markup commands can be defined
-with the @code{define-markup-command} Scheme macro.
-
-@lisp
-(define-markup-command (@var{command-name} @var{layout} @var{props} @var{arg1} @var{arg2} ...)
- (@var{arg1-type?} @var{arg2-type?} ...)
- ..command body..)
-@end lisp
-
-The arguments are
-
-@table @var
-@item argi
-@var{i}th command argument
-@item argi-type?
-a type predicate for the i@var{th} argument
-@item layout
-the @q{layout} definition
-@item props
-a list of alists, containing all active properties.
-@end table
-
-As a simple example, we show how to add a @code{\smallcaps} command,
-which selects a small caps font. Normally we could select the
-small caps font,
-
-@example
-\markup @{ \override #'(font-shape . caps) Text-in-caps @}
-@end example
-
-@noindent
-This selects the caps font by setting the @code{font-shape} property to
-@code{#'caps} for interpreting @code{Text-in-caps}.
-
-To make the above available as @code{\smallcaps} command, we must
-define a function using @code{define-markup-command}. The command should
-take a single argument of type @code{markup}. Therefore the start of the
-definition should read
-
-@example
-(define-markup-command (smallcaps layout props argument) (markup?)
-@end example
-
-@noindent
-
-What follows is the content of the command: we should interpret
-the @code{argument} as a markup, i.e.,
-
-@example
-(interpret-markup layout @dots{} argument)
-@end example
-
-@noindent
-This interpretation should add @code{'(font-shape . caps)} to the active
-properties, so we substitute the following for the @dots{} in the
-above example:
-
-@example
-(cons (list '(font-shape . caps) ) props)
-@end example
-
-@noindent
-The variable @code{props} is a list of alists, and we prepend to it by
-cons'ing a list with the extra setting.
-
-
-Suppose that we are typesetting a recitative in an opera and
-we would like to define a command that will show character names in a
-custom manner. Names should be printed with small caps and moved a
-bit to the left and top. We will define a @code{\character} command
-which takes into account the necessary translation and uses the newly
-defined @code{\smallcaps} command:
-
-@example
-#(define-markup-command (character layout props name) (string?)
- "Print the character name in small caps, translated to the left and
- top. Syntax: \\character #\"name\""
- (interpret-markup layout props
- (markup #:hspace 0 #:translate (cons -3 1) #:smallcaps name)))
-@end example
-
-There is one complication that needs explanation: texts above and below
-the staff are moved vertically to be at a certain distance (the
-@code{padding} property) from the staff and the notes. To make sure
-that this mechanism does not annihilate the vertical effect of our
-@code{#:translate}, we add an empty string (@code{#:hspace 0}) before the
-translated text. Now the @code{#:hspace 0} will be put above the notes,
-and the
-@code{name} is moved in relation to that empty string. The net effect is
-that the text is moved to the upper left.
-
-The final result is as follows:
-
-@example
-@{
- c''^\markup \character #"Cleopatra"
- e'^\markup \character #"Giulio Cesare"
-@}
-@end example
-
-@lilypond[quote,ragged-right]
-#(define-markup-command (smallcaps layout props str) (string?)
- "Print the string argument in small caps. Syntax: \\smallcaps #\"string\""
- (interpret-markup layout props
- (make-line-markup
- (map (lambda (s)
- (if (= (string-length s) 0)
- s
- (markup #:large (string-upcase (substring s 0 1))
- #:translate (cons -0.6 0)
- #:tiny (string-upcase (substring s 1)))))
- (string-split str #\Space)))))
-
-#(define-markup-command (character layout props name) (string?)
- "Print the character name in small caps, translated to the left and
- top. Syntax: \\character #\"name\""
- (interpret-markup layout props
- (markup #:hspace 0 #:translate (cons -3 1) #:smallcaps name)))
-
-{
- c''^\markup \character #"Cleopatra" c'' c'' c''
- e'^\markup \character #"Giulio Cesare" e' e' e'
-}
-@end lilypond
-
-We have used the @code{caps} font shape, but suppose that our font
-does not have a small-caps variant. In that case we have to fake
-the small caps font by setting a string in upcase with the first
-letter a little larger:
-
-@example
-#(define-markup-command (smallcaps layout props str) (string?)
- "Print the string argument in small caps."
- (interpret-markup layout props
- (make-line-markup
- (map (lambda (s)
- (if (= (string-length s) 0)
- s
- (markup #:large (string-upcase (substring s 0 1))
- #:translate (cons -0.6 0)
- #:tiny (string-upcase (substring s 1)))))
- (string-split str #\Space)))))
-@end example
-
-The @code{smallcaps} command first splits its string argument into
-tokens separated by spaces (@code{(string-split str #\Space)}); for
-each token, a markup is built with the first letter made large and
-upcased (@code{#:large (string-upcase (substring s 0 1))}), and a
-second markup built with the following letters made tiny and upcased
-(@code{#:tiny (string-upcase (substring s 1))}). As LilyPond
-introduces a space between markups on a line, the second markup is
-translated to the left (@code{#:translate (cons -0.6 0) ...}). Then,
-the markups built for each token are put in a line by
-@code{(make-line-markup ...)}. Finally, the resulting markup is passed
-to the @code{interpret-markup} function, with the @code{layout} and
-@code{props} arguments.
-
-Note: there is now an internal command @code{\smallCaps} which can
-be used to set text in small caps. See
-@ref{Text markup commands}, for details.
-
-@knownissues
-
-Currently, the available combinations of arguments (after the standard
-@var{layout} and @var{props} arguments) to a markup command defined with
-@code{define-markup-command} are limited as follows.
-
-@table @asis
-@item (no argument)
-@itemx @var{list}
-@itemx @var{markup}
-@itemx @var{markup markup}
-@itemx @var{scm}
-@itemx @var{scm markup}
-@itemx @var{scm scm}
-@itemx @var{scm scm markup}
-@itemx @var{scm scm markup markup}
-@itemx @var{scm markup markup}
-@itemx @var{scm scm scm}
-@end table
-
-@noindent
-In the above table, @var{scm} represents native Scheme data types like
-@q{number} or @q{string}.
-
-As an example, it is not possible to use a markup command @code{foo} with
-four arguments defined as
-
-@example
-#(define-markup-command (foo layout props
- num1 str1 num2 str2)
- (number? string? number? string?)
- ...)
-@end example
-
-@noindent
-If you apply it as, say,
-
-@example
-\markup \foo #1 #"bar" #2 #"baz"
-@end example
-
-@cindex Scheme signature
-@cindex signature, Scheme
-@noindent
-@command{lilypond} complains that it cannot parse @code{foo} due to its
-unknown Scheme signature.
-
-
-@node New markup list command definition
-@subsection New markup list command definition
-Markup list commands are defined with the
-@code{define-markup-list-command} Scheme macro, which is similar to the
-@code{define-markup-command} macro described in
-@ref{New markup command definition}, except that where the latter returns
-a single stencil, the former returns a list stencils.
-
-In the following example, a @code{\paragraph} markup list command is
-defined, which returns a list of justified lines, the first one being
-indented. The indent width is taken from the @code{props} argument.
-@example
-#(define-markup-list-command (paragraph layout props args) (markup-list?)
- (let ((indent (chain-assoc-get 'par-indent props 2)))
- (interpret-markup-list layout props
- (make-justified-lines-markup-list (cons (make-hspace-markup indent)
- args)))))
-@end example
-
-Besides the usual @code{layout} and @code{props} arguments, the
-@code{paragraph} markup list command takes a markup list argument, named
-@code{args}. The predicate for markup lists is @code{markup-list?}.
-
-First, the function gets the indent width, a property here named
-@code{par-indent}, from the property list @code{props} If the property
-is not found, the default value is @code{2}. Then, a list of justified
-lines is made using the @code{make-justified-lines-markup-list}
-function, which is related to the @code{\justified-lines}
-built-in markup list command. An horizontal space is added at the
-beginning using the @code{make-hspace-markup} function. Finally, the
-markup list is interpreted using the @code{interpret-markup-list}
-function.
-
-This new markup list command can be used as follows:
-@example
-\markuplines @{
- \paragraph @{
- The art of music typography is called \italic @{(plate) engraving.@}
- The term derives from the traditional process of music printing.
- Just a few decades ago, sheet music was made by cutting and stamping
- the music into a zinc or pewter plate in mirror image.
- @}
- \override-lines #'(par-indent . 4) \paragraph @{
- The plate would be inked, the depressions caused by the cutting
- and stamping would hold ink. An image was formed by pressing paper
- to the plate. The stamping and cutting was completely done by
- hand.
- @}
-@}
-@end example
-
-@node Contexts for programmers
-@section Contexts for programmers
-
-@menu
-* Context evaluation::
-* Running a function on all layout objects::
-@end menu
-
-@node Context evaluation
-@subsection Context evaluation
-
-@cindex calling code during interpreting
-@funindex \applyContext
-
-Contexts can be modified during interpretation with Scheme code. The
-syntax for this is
-@example
-\applyContext @var{function}
-@end example
-
-@var{function} should be a Scheme function taking a single argument,
-being the context to apply it to. The following code will print the
-current bar number on the standard output during the compile:
-
-@example
-\applyContext
- #(lambda (x)
- (format #t "\nWe were called in barnumber ~a.\n"
- (ly:context-property x 'currentBarNumber)))
-@end example
-
-
-
-@node Running a function on all layout objects
-@subsection Running a function on all layout objects
-
-
-@cindex calling code on layout objects
-@funindex \applyOutput
-
-
-The most versatile way of tuning an object is @code{\applyOutput}. Its
-syntax is
-@example
-\applyOutput @var{context} @var{proc}
-@end example
-
-@noindent
-where @var{proc} is a Scheme function, taking three arguments.
-
-When interpreted, the function @var{proc} is called for every layout
-object found in the context @var{context}, with the following
-arguments:
-@itemize
-@item the layout object itself,
-@item the context where the layout object was created, and
-@item the context where @code{\applyOutput} is processed.
-@end itemize
-
-
-In addition, the cause of the layout object, i.e., the music
-expression or object that was responsible for creating it, is in the
-object property @code{cause}. For example, for a note head, this is a
-@rinternals{NoteHead} event, and for a @rinternals{Stem} object,
-this is a @rinternals{NoteHead} object.
-
-Here is a function to use for @code{\applyOutput}; it blanks
-note-heads on the center-line:
-
-@example
-(define (blanker grob grob-origin context)
- (if (and (memq (ly:grob-property grob 'interfaces)
- note-head-interface)
- (eq? (ly:grob-property grob 'staff-position) 0))
- (set! (ly:grob-property grob 'transparent) #t)))
-@end example
-
-
-@node Scheme procedures as properties
-@section Scheme procedures as properties
-
-Properties (like thickness, direction, etc.) can be set at fixed values
-with \override, e.g.
-
-@example
-\override Stem #'thickness = #2.0
-@end example
-
-Properties can also be set to a Scheme procedure,
-
-@lilypond[fragment,verbatim,quote,relative=2]
-\override Stem #'thickness = #(lambda (grob)
- (if (= UP (ly:grob-property grob 'direction))
- 2.0
- 7.0))
-c b a g b a g b
-@end lilypond
-
-@noindent
-In this case, the procedure is executed as soon as the value of the
-property is requested during the formatting process.
-
-Most of the typesetting engine is driven by such callbacks.
-Properties that typically use callbacks include
-
-@table @code
-@item stencil
- The printing routine, that constructs a drawing for the symbol
-@item X-offset
- The routine that sets the horizontal position
-@item X-extent
- The routine that computes the width of an object
-@end table
-
-The procedure always takes a single argument, being the grob.
-
-If routines with multiple arguments must be called, the current grob
-can be inserted with a grob closure. Here is a setting from
-@code{AccidentalSuggestion},
-
-@example
-(X-offset .
- ,(ly:make-simple-closure
- `(,+
- ,(ly:make-simple-closure
- (list ly:self-alignment-interface::centered-on-x-parent))
- ,(ly:make-simple-closure
- (list ly:self-alignment-interface::x-aligned-on-self)))))
-@end example
-
-@noindent
-In this example, both @code{ly:self-alignment-interface::x-aligned-on-self} and
-@code{ly:self-alignment-interface::centered-on-x-parent} are called
-with the grob as argument. The results are added with the @code{+}
-function. To ensure that this addition is properly executed, the whole
-thing is enclosed in @code{ly:make-simple-closure}.
-
-In fact, using a single procedure as property value is equivalent to
-
-@example
-(ly:make-simple-closure (ly:make-simple-closure (list @var{proc})))
-@end example
-
-@noindent
-The inner @code{ly:make-simple-closure} supplies the grob as argument
-to @var{proc}, the outer ensures that result of the function is
-returned, rather than the @code{simple-closure} object.
-
-
-@node Using Scheme code instead of \tweak
-@section Using Scheme code instead of @code{\tweak}
-
-The main disadvantage of @code{\tweak} is its syntactical
-inflexibility. For example, the following produces a syntax error.
-
-@example
-F = \tweak #'font-size #-3 -\flageolet
-
-\relative c'' @{
- c4^\F c4_\F
-@}
-@end example
-
-@noindent
-With other words, @code{\tweak} doesn't behave like an articulation
-regarding the syntax; in particular, it can't be attached with
-@code{^} and @code{_}.
-
-Using Scheme, this problem can be circumvented. The route to the
-result is given in @ref{Adding articulation to notes (example)},
-especially how to use @code{\displayMusic} as a helping guide.
-
-@example
-F = #(let ((m (make-music 'ArticulationEvent
- 'articulation-type "flageolet")))
- (set! (ly:music-property m 'tweaks)
- (acons 'font-size -3
- (ly:music-property m 'tweaks)))
- m)
-
-\relative c'' @{
- c4^\F c4_\F
-@}
-@end example
-
-@noindent
-Here, the @code{tweaks} properties of the flageolet object
-@code{m} (created with @code{make-music}) are extracted with
-@code{ly:music-property}, a new key-value pair to change the
-font size is prepended to the property list with the
-@code{acons} Scheme function, and the result is finally
-written back with @code{set!}. The last element of the
-@code{let} block is the return value, @code{m} itself.
-
-
-
-@node Difficult tweaks
-@section Difficult tweaks
-
-There are a few classes of difficult adjustments.
-
-@itemize
-
-
-@item
-One type of difficult adjustment is the appearance of spanner objects,
-such as slur and tie. Initially, only one of these objects is created,
-and they can be adjusted with the normal mechanism. However, in some
-cases the spanners cross line breaks. If this happens, these objects
-are cloned. A separate object is created for every system that it is
-in. These are clones of the original object and inherit all
-properties, including @code{\override}s.
-
-
-In other words, an @code{\override} always affects all pieces of a
-broken spanner. To change only one part of a spanner at a line break,
-it is necessary to hook into the formatting process. The
-@code{after-line-breaking} callback contains the Scheme procedure that
-is called after the line breaks have been determined, and layout
-objects have been split over different systems.
-
-In the following example, we define a procedure
-@code{my-callback}. This procedure
-
-@itemize
-@item
-determines if we have been split across line breaks
-@item
-if yes, retrieves all the split objects
-@item
-checks if we are the last of the split objects
-@item
-if yes, it sets @code{extra-offset}.
-@end itemize
-
-This procedure is installed into @rinternals{Tie}, so the last part
-of the broken tie is translated up.
-
-@lilypond[quote,verbatim,ragged-right]
-#(define (my-callback grob)
- (let* (
- ; have we been split?
- (orig (ly:grob-original grob))
-
- ; if yes, get the split pieces (our siblings)
- (siblings (if (ly:grob? orig)
- (ly:spanner-broken-into orig) '() )))
-
- (if (and (>= (length siblings) 2)
- (eq? (car (last-pair siblings)) grob))
- (ly:grob-set-property! grob 'extra-offset '(-2 . 5)))))
-
-\relative c'' {
- \override Tie #'after-line-breaking =
- #my-callback
- c1 ~ \break c2 ~ c
-}
-@end lilypond
-
-@noindent
-When applying this trick, the new @code{after-line-breaking} callback
-should also call the old one @code{after-line-breaking}, if there is
-one. For example, if using this with @code{Hairpin},
-@code{ly:hairpin::after-line-breaking} should also be called.
-
-
-@item Some objects cannot be changed with @code{\override} for
-technical reasons. Examples of those are @code{NonMusicalPaperColumn}
-and @code{PaperColumn}. They can be changed with the
-@code{\overrideProperty} function, which works similar to @code{\once
-\override}, but uses a different syntax.
-
-@example
-\overrideProperty
-#"Score.NonMusicalPaperColumn" % Grob name
-#'line-break-system-details % Property name
-#'((next-padding . 20)) % Value
-@end example
-
-Note, however, that @code{\override}, applied to
-@code{NonMusicalPaperColumn} and @code{PaperColumn}, still works as
-expected within @code{\context} blocks.
-
-@end itemize
-
-
-
-
-
projects / lilypond.git / blobdiff