Advanced tweaks may be performed by using Scheme. If you are
not familiar with Scheme, you may wish to read our
-@ref{Scheme tutorial}.
+@rlearning{Scheme tutorial}.
@menu
* Music functions::
music expression.
That is why the form
-that is returned is the @code{(make-music ...)}. With the
+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
@subsection Functions without arguments
In most cases a function without arguments should be written
-with an identifier,
+with an variable,
@example
dolce = \markup@{ \italic \bold dolce @}
@example
displayBarNum =
#(define-music-function (parser location) ()
- (if (eq? #t (ly:get-option display-bar-numbers))
+ (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 lilypond with
+invoke @command{lilypond} with
@example
lilypond -d display-bar-numbers FILENAME.ly
Due to parser lookahead
In this example, the assignment happens after parser has verified that
-nothing interesting happens after @code{traLaLa = @{ ... @}}. Without
+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.
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
+@ref{Void functions}, or
@example
#(define (nopc)
@end example
-@refbugs
+@knownissues
-Mixing Scheme and LilyPond identifiers is not possible with the
+Mixing Scheme and LilyPond variables is not possible with the
@code{--safe} option.
of a piece of music in whole notes.
A music object has three kinds of types:
-@itemize @bullet
+@itemize
@item
music name: Each music expression has a name. For example, a note
leads to a @internalsref{NoteEvent}, and @code{\simultaneous} leads to
a @internalsref{SimultaneousMusic}. A list of all expressions
-available is in the Program reference manual, under
+available is in the Internals Reference manual, under
@internalsref{Music expressions}.
@item
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
-Program reference, under
+Internals Reference, under
@internalsref{Music classes}.
@item
@subsection Doubling a note with slurs (example)
Suppose we want to create a function which translates
-input like @samp{a} into @samp{a( a)}. We begin
+input like @code{a} into @code{a( a)}. We begin
by examining the internal representation of the music
we want to end up with.
(set! place new-value)
@end example
-Here, what we want to set (the "place") is the "elements" property of
-@code{result-event-chord} expression
+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)
(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{MarcatoEvent} expression, which we copy from the
+@code{ArticulationEvent} expression, which we copy from the
@code{\displayMusic} output,
@example
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 @code{MarcatoEvent} to its elements
+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.
* Markup construction in Scheme::
* How markups work internally::
* New markup command definition::
+* New markup list command definition::
@end menu
@ref{New markup command definition}).
-@refbugs
+@knownissues
The markup-list argument of commands such as @code{#:line},
@code{#:center}, and @code{#:column} cannot be a variable or
Note: there is now an internal command @code{\smallCaps} which can
be used to set text in small caps. See
-@ref{Overview of text markup commands} for details.
+@ref{Text markup commands}, for details.
+@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 later 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
When interpreted, the function @var{proc} is called for every layout
object found in the context @var{context}, with the following
arguments:
-@itemize @bullet
+@itemize
@item the layout object itself,
@item the context where the layout object was created, and
@item the context where @code{\applyOutput} is processed.
@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
+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
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