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.
+ version that you are working on. For details, see the Contributors'
+ Guide, node Updating translation committishes..
@end ignore
-@c \version "2.12.0"
+@c \version "2.16.0"
@node Changing defaults
@chapter Changing defaults
options available in LilyPond. It is written as a HTML document,
which is available
@c leave the @uref as one long line.
-@uref{http://@/lilypond@/.org/@/doc/@/stable/@/Documentation/@/user/@/lilypond@/-internals/,on@/-line},
+@uref{http://@/lilypond@/.org/@/doc/@/stable/@/Documentation/@/internals/,on@/-line},
and is also included with the LilyPond documentation package.
Internally, LilyPond uses Scheme (a LISP dialect) to provide
infrastructure. Overriding layout decisions in effect accesses the
program internals, which requires Scheme input. Scheme elements are
-introduced in a @code{.ly} file with the hash mark
-@code{#}.@footnote{@rlearning{Scheme tutorial}, contains a short tutorial
-on entering numbers, lists, strings, and symbols in Scheme.}
+introduced in a @file{.ly} file with the hash
+mark@tie{}@code{#}.@footnote{@rextend{Scheme tutorial}, contains a
+short tutorial on entering numbers, lists, strings, and symbols in
+Scheme.}
@menu
* Modifying properties::
* Useful concepts and properties::
* Advanced tweaks::
+* Using music functions::
@end menu
* Modifying context plug-ins::
* Changing context default settings::
* Defining new contexts::
-* Aligning contexts::
+* Context layout order::
@end menu
-
@seealso
Learning Manual:
@rlearning{Contexts and engravers}.
-Installed files:
-@file{ly/@/engraver@/-init@/.ly},
-@file{ly/@/performer@/-init@/.ly}.
+Installed Files:
+@file{ly/engraver-init.ly},
+@file{ly/performer-init.ly}.
Snippets:
@rlsr{Contexts and engravers}.
@node Score - the master of all contexts
@unnumberedsubsubsec Score - the master of all contexts
-This is the top level notation context. No other context can
-contain a Score context. By default the Score context handles
+This is the top level notation context. No other context can
+contain a Score context. By default the Score context handles
the administration of time signatures and makes sure that items
such as clefs, time signatures, and key-signatures are aligned
across staves.
A Score context is instantiated implicitly when a
@code{\score @{@dots{}@}} or @code{\layout @{@dots{}@}} block is
-processed, or explicitly when a @code{\new Score} command is
-executed.
+processed.
@node Top-level contexts - staff containers
@unnumberedsubsubsec Top-level contexts - staff containers
@strong{@emph{StaffGroup}}
Groups staves while adding a bracket on the left side, grouping
-the staves together. The bar lines of the contained staves are
+the staves together. The bar lines of the contained staves are
connected vertically. @code{StaffGroup} only consists of a collection
of staves, with a bracket in front and spanning bar lines.
@node Creating contexts
@subsection Creating contexts
-@c TODO \new Score and \score
@c TODO more complete descriptions rather than learning style
For scores with only one voice and one staff, contexts are
staves. Each part that should be on its own staff, is preceded with
@code{\new Staff}.
-@lilypond[quote,verbatim,relative=2,ragged-right,fragment]
+@lilypond[quote,verbatim,relative=2,ragged-right]
<<
\new Staff { c4 c }
\new Staff { d4 d }
This variant is used with music expressions that can be interpreted at
several levels. For example, the @code{\applyOutput} command (see
-@ref{Running a function on all layout objects}). Without an explicit
+@rextend{Running a function on all layout objects}). Without an explicit
@code{\context}, it is usually applied to @code{Voice}
@example
@c TODO Should this be Modifying engravers or Modifying contexts?
-Notation contexts (like @code{Score} and @code{Staff}) not only
-store properties,
-they also contain plug-ins called @q{engravers} that create notation
-elements. For example, the @code{Voice} context contains a
-@code{Note_head_engraver} and the @code{Staff} context contains a
-@code{Key_signature_engraver}.
+Notation contexts (like @code{Score} and @code{Staff}) not only store
+properties, they also contain plug-ins called @q{engravers} that create
+notation elements. For example, the @code{Voice} context contains a
+@code{Note_heads_engraver} and the @code{Staff} context contains a
+@code{Key_engraver}.
For a full a description of each plug-in, see
@ifhtml
example which removes @code{Time_signature_engraver} and
@code{Clef_engraver} from a @code{Staff} context,
-@lilypond[quote,relative=1,verbatim,fragment]
+@lilypond[quote,relative=1,verbatim]
<<
\new Staff {
f2 g
@cindex polymetric scores
@cindex Time signatures, multiple
-@lilypond[quote,relative=1,ragged-right,verbatim,fragment]
-\new Score \with {
- \remove "Timing_translator"
- \remove "Default_bar_line_engraver"
-} <<
+@lilypond[quote,verbatim]
+\score {
+ <<
+ \new Staff \with {
+ \consists "Timing_translator"
+ \consists "Default_bar_line_engraver"
+ } {
+ \time 3/4
+ c4 c c c c c
+ }
\new Staff \with {
\consists "Timing_translator"
\consists "Default_bar_line_engraver"
} {
- \time 3/4
+ \time 2/4
c4 c c c c c
}
- \new Staff \with {
- \consists "Timing_translator"
- \consists "Default_bar_line_engraver"
- } {
- \time 2/4
- c4 c c c c c
- }
>>
+\layout {
+ \context {
+ \Score
+ \remove "Timing_translator"
+ \remove "Default_bar_line_engraver"
+ }
+ }
+}
@end lilypond
@knownissues
-Usually the order in which the engravers are specified
-does not matter, but in a few special cases the order
-is important, for example where one engraver writes
-a property and another reads it, or where one engraver
-creates a grob and another must process it. The order in
-which the engravers are specified is the order in which
-they are called to carry out their processing.
+The order in which the engravers are specified is the order in
+which they are called to carry out their processing. Usually the
+order in which the engravers are specified does not matter, but in
+a few special cases the order is important, for example where one
+engraver writes a property and another reads it, or where one
+engraver creates a grob and another must process it.
+
+The following orderings are important:
+
+@itemize
+@item
+the @code{Bar_engraver} must normally be first,
+
+@item
+the @code{New_fingering_engraver} must come before the
+@code{Script_column_engraver},
+
+@item
+the @code{Timing_translator} must come before the
+@code{Bar_number_engraver}.
+
+@end itemize
+
+@seealso
+Installed Files:
+@file{ly/engraver-init.ly}.
-The following orderings are important: the
-@code{Bar_engraver} must normally be first, and
-the @code{New_fingering_engraver} must come before
-the @code{Script_column_engraver}. There may be others
-with ordering dependencies.
@node Changing context default settings
@subsection Changing context default settings
+@cindex default context properties, changing
+@cindex context properties, changing defaults
+
+Context and grob properties can be changed with @code{\set}
+and @code{\override} commands, as described in
+@ref{Modifying properties}. These commands create music events,
+making the changes take effect at the point in time the music
+is being processed.
+
+In contrast, this section explains how to change the @emph{default}
+values of context and grob properties at the time the context is
+created. There are two ways of doing this. One modifies the default
+values in all contexts of a particular type, the other modifies the
+default values in just one particular instance of a context.
+
+@menu
+* Changing all contexts of the same type::
+* Changing just one specific context::
+* Order of precedence::
+@end menu
+
+@node Changing all contexts of the same type
+@unnumberedsubsubsec Changing all contexts of the same type
+
+@cindex \context in \layout block
+@funindex \context
+@funindex \layout
+
The context settings which are to be used by default in
-@code{Score}, @code{Staff} and @code{Voice} contexts may be specified
-in a @code{\layout} block, as illustrated in the following example.
+@code{Score}, @code{Staff}, @code{Voice} and other contexts may be
+specified in a @code{\context} block within any @code{\layout} block.
The @code{\layout} block should be placed within the @code{\score}
-block to which it is to apply, but outside any music.
+block to which it is to apply, after the music.
+
+@example
+\layout @{
+ \context @{
+ \Voice
+ [context settings for all Voice contexts]
+ @}
+ \context @{
+ \Staff
+ [context settings for all Staff contexts]
+ @}
+@}
+@end example
-Note that the @code{\set} command itself and the context must be
-omitted when the context default values are specified in this way:
+The following types of settings may be specified:
+
+@itemize
+@item
+An @code{\override} command, but with the context name omitted
@lilypond[quote,verbatim]
\score {
\relative c'' {
- a4^"Really small, thicker stems, no time signature" a a a
- a a a a
+ a4^"Thicker stems" a a a
+ a4 a a\ff a
}
\layout {
\context {
\Staff
- fontSize = #-4
\override Stem #'thickness = #4.0
- \remove "Time_signature_engraver"
}
}
}
@end lilypond
-In this example, the @code{\Staff} command specifies that the
-subsequent specifications are to be applied to all staves within
-this score block.
+@item
+Directly setting a context property
-Modifications can be made to the @code{Score} context or all
-@code{Voice} contexts in a similar way.
+@lilypond[quote,verbatim]
+\score {
+ \relative c'' {
+ a4^"Smaller font" a a a
+ a4 a a\ff a
+ }
+ \layout {
+ \context {
+ \Staff
+ fontSize = #-4
+ }
+ }
+}
+@end lilypond
-@knownissues
+@item
+A predefined command such as @code{\dynamicUp} or a music
+expression like @code{\accidentalStyle "dodecaphonic"}
-It is not possible to collect context changes in a variable and apply
-them to a @code{\context} definition by referring to that variable.
+@lilypond[quote,verbatim]
+\score {
+ \relative c'' {
+ a4^"Dynamics above" a a a
+ a4 a a\ff a
+ }
+ \layout {
+ \context {
+ \Voice
+ \dynamicUp
+ }
+ \context {
+ \Staff
+ \accidentalStyle "dodecaphonic"
+ }
+ }
+}
+@end lilypond
-The @code{\RemoveEmptyStaffContext} will overwrite your current
-@code{\Staff} settings. If you wish to change the defaults for a
-staff which uses @code{\RemoveEmptyStaffContext}, you must do so
-after calling @code{\RemoveEmptyStaffContext}, ie
+@item
+A user-defined variable containing a @code{\with} block; for details
+of the @code{\with} block see
+@ref{Changing just one specific context}.
-@example
-\layout @{
- \context @{
- \RemoveEmptyStaffContext
+@lilypond[quote,verbatim]
+StaffDefaults = \with {
+ fontSize = #-4
+}
- \override Stem #'thickness = #4.0
- @}
+\score {
+ \new Staff {
+ \relative c'' {
+ a4^"Smaller font" a a a
+ a4 a a a
+ }
+ }
+ \layout {
+ \context {
+ \Staff
+ \StaffDefaults
+ }
+ }
+}
+@end lilypond
+
+@end itemize
+
+Property-setting commands can be placed in a @code{\layout} block
+without being enclosed in a @code{\context} block. Such settings
+are equivalent to including the same property-setting commands at
+the start of every context of the type specified. If no context
+is specified @emph{every} bottom-level context is affected, see
+@ref{Bottom-level contexts - voices}. The syntax of a
+property-setting command in a @code{\layout} block is the same as
+the same command written in the music stream.
+
+@lilypond[quote,verbatim]
+\score {
+ \new Staff {
+ \relative c'' {
+ a4^"Smaller font" a a a
+ a4 a a a
+ }
+ }
+ \layout {
+ \accidentalStyle "dodecaphonic"
+ \set fontSize = #-4
+ \override Voice.Stem #'thickness = #4.0
+ }
+}
+@end lilypond
+
+
+@node Changing just one specific context
+@unnumberedsubsubsec Changing just one specific context
+
+@cindex \with
+@funindex \with
+
+The context properties of just one specific context instance can be
+changed in a @code{\with} block. All other context instances of the
+same type retain the default settings built into LilyPond and modified
+by any @code{\layout} block within scope. The @code{\with} block
+must be placed immediately after the @code{\new} @var{context-type}
+command:
+
+@example
+\new Staff
+\with @{
+ [context settings for this context instance only]
+@} @{
+...
@}
@end example
-@c TODO: add \with in here.
+The following types of settings may be specified:
+
+@itemize
+@item
+An @code{\override} command, but with the context name omitted
+
+@lilypond[quote,verbatim]
+\score {
+ \new Staff {
+ \new Voice
+ \with {
+ \override Stem #'thickness = #4.0
+ }
+ {
+ \relative c'' {
+ a4^"Thick stems" a a a
+ a4 a a a
+ }
+ }
+ }
+}
+@end lilypond
+
+@item
+Directly setting a context property
+
+@lilypond[quote,verbatim]
+\score {
+ <<
+ \new Staff {
+ \relative c'' {
+ a4^"Default font" a a a
+ a4 a a a
+ }
+ }
+ \new Staff
+ \with {
+ fontSize = #-4
+ } {
+ \relative c'' {
+ a4^"Smaller font" a a a
+ a4 a a a
+ }
+ }
+ >>
+}
+@end lilypond
+
+@item
+A predefined command such as @code{\dynamicUp}
+
+@lilypond[quote,verbatim]
+\score {
+ <<
+ \new Staff {
+ \new Voice {
+ \relative c'' {
+ a4^"Dynamics below" a a a
+ a4 a a\ff a
+ }
+ }
+ }
+ \new Staff
+ \with { \accidentalStyle "dodecaphonic" }
+ {
+ \new Voice
+ \with { \dynamicUp }
+ {
+ \relative c'' {
+ a4^"Dynamics above" a a a
+ a4 a a\ff a
+ }
+ }
+ }
+ >>
+}
+@end lilypond
+
+@end itemize
+
+@node Order of precedence
+@unnumberedsubsubsec Order of precedence
+
+The value of a property which applies at a particular time is
+determined as follows:
+
+@itemize
+@item
+if an @code{\override} or @code{\set} command in the input stream is
+in effect that value is used,
+
+@item
+otherwise the default value taken from a @code{\with} statement
+on the context initiation statement is used,
+@item
+otherwise the default value taken from the most recent appropriate
+@code{\context} block in the @code{\layout} blocks is used,
+
+@item
+otherwise the LilyPond built-in default is used.
+@end itemize
+
+@seealso
+Learning Manual:
+@rlearning{Modifying context properties}.
+
+Notation Reference:
+@ref{Contexts explained},
+@ref{Bottom-level contexts - voices},
+@ref{The set command},
+@ref{The override command},
+@ref{The \layout block}.
@node Defining new contexts
squashedPosition = #0
\override NoteHead #'style = #'slash
\override Stem #'transparent = ##t
+ \override Flag #'transparent = ##t
\alias Voice
}
\context { \Staff
@example
\override NoteHead #'style = #'slash
\override Stem #'transparent = ##t
+\override Flag #'transparent = ##t
@end example
All these plug-ins have to cooperate, and this is achieved with a
squashedPosition = #0
\override NoteHead #'style = #'slash
\override Stem #'transparent = ##t
+ \override Flag #'transparent = ##t
\alias Voice
@}
@end example
@end example
-@node Aligning contexts
-@subsection Aligning contexts
+@node Context layout order
+@subsection Context layout order
-New contexts may be aligned above or below existing contexts. This
-could be useful in setting up a vocal staff (@rlearning{Vocal ensembles}) and
-in ossia,
+@cindex contexts, layout order
+@funindex \accepts
+@funindex \denies
-@c TODO Better example needed. Ref LM, and expand on it.
+Contexts are normally positioned in a system from top to bottom
+in the order in which they are encountered in the input file. When
+contexts are nested, the outer context will include inner nested
+contexts as specified in the input file, provided the inner contexts
+are included in the outer context's @qq{accepts} list. Nested
+contexts which are not included in the outer context's @qq{accepts}
+list will be repositioned below the outer context rather than nested
+within it.
-@cindex ossia
-@funindex alignAboveContext
-@funindex alignBelowContext
+The @qq{accepts} list of a context can be changed with the
+@code{\accepts} and @code{\denies} commands. @code{\accepts} adds a
+context to the @qq{accepts} list and @code{\denies} removes a context
+from the list. For example, it would not normally be desirable for
+chord names to be nested within a @code{Staff} context, so the
+@code{ChordNames} context is not included by default in the @qq{accepts}
+list of the @code{Staff} context, but if this were to be required it can
+be done:
-@lilypond[quote,ragged-right]
-ossia = { f4 f f f }
-\score{
- \relative c' \new Staff = "main" {
- c4 c c c
- <<
- \new Staff \with { alignAboveContext = #"main" } \ossia
- { d8 f d f d f d f }
- >>
+@lilypond[verbatim,quote]
+\score {
+ \new Staff {
+ c' d' e' f'
+ \chords { d1:m7 b1:min7.5- }
}
}
@end lilypond
-@cindex nested contexts
-@cindex contexts, nested
-
-@funindex \accepts
-@funindex \denies
-
-Contexts like @code{PianoStaff} can contain other contexts
-nested within them. Contexts which are acceptable for nesting
-are defined by the @qq{accepts} list of a context. Contexts
-which are not in this list are placed below the outer context
-in the printed score.
-For example, the @code{PianoStaff} context is defined by default
-to accept @code{Staff} and @code{FiguredBass} contexts within
-it, but not (for example) a @code{Lyrics} context. So in the
-following structure the lyrics are placed below the piano staff
-rather than between the two staves:
-
-@lilypond[verbatim,quote,relative=1]
-\new PianoStaff
-<<
- \new Staff { e4 d c2 }
- \addlyrics { Three blind mice }
+@lilypond[verbatim,quote]
+\score {
\new Staff {
- \clef "bass"
- { c,1 }
+ c' d' e' f'
+ \chords { d1:m7 b1:min7.5- }
}
->>
+ \layout {
+ \context {
+ \Staff
+ \accepts "ChordNames"
+ }
+ }
+}
@end lilypond
-The @qq{accepts} list of a context can be modified to include
-additional nested contexts, so if we wanted the lyrics to appear
-between the two staves we could use:
+@code{\denies} is mainly used when a new context is being based on
+another, but the required nesting differs. For example, the
+@code{VaticanaStaff} context is based on the @code{Staff} context, but
+with the @code{VaticanaVoice} context substituted for the @code{Voice}
+context in the @qq{accepts} list.
-@lilypond[verbatim,quote,relative=1]
-\new PianoStaff \with { \accepts Lyrics }
-<<
- \new Staff { e4 d c2 }
- \addlyrics { Three blind mice }
- \new Staff {
- \clef "bass"
- { c,1 }
- }
->>
-@end lilypond
+Note that a context will be silently created implicitly if a command
+is encountered when there is no suitable context available to
+contain it. This can give rise to unexpected new staves or scores.
+
+@cindex alignAboveContext
+@cindex alignBelowContext
+@funindex alignAboveContext
+@funindex alignBelowContext
+
+Sometimes a context is required to exist for just a brief period, a
+good example being the staff context for an ossia. This is usually
+achieved by introducing the context definition at the appropriate
+place in parallel with corresponding section of the main music.
+By default, the temporary context will be placed below all the
+existing contexts. To reposition it above the context called
+@qq{main}, it should be defined like this:
+
+@example
+@code{\new Staff \with @{ alignAboveContext = #"main" @} }
+@end example
+
+A similar situation arises when positioning a temporary lyrics
+context within a multi-staved layout such as a @code{ChoirStaff},
+for example, when adding a second verse to a repeated section.
+By default the temporary lyrics context will be placed beneath the
+lower staves. By defining the temporary lyrics context with
+@code{alignBelowContext} it can be positioned correctly beneath
+the (named) lyrics context containing the first verse.
+
+Examples showing this repositioning of temporary contexts can be
+found elsewhere --- see @rlearning{Nesting music expressions},
+@ref{Modifying single staves} and @ref{Techniques specific to lyrics}.
+
+@seealso
+Learning Manual:
+@rlearning{Nesting music expressions}.
+
+Notation Reference:
+@ref{Modifying single staves},
+@ref{Techniques specific to lyrics}.
+
+Application Usage:
+@rprogram{An extra staff appears}.
+
+Installed Files:
+@file{ly/engraver-init.ly}.
-The opposite of @code{\accepts} is @code{\denies}; this removes a
-context from the @qq{accepts} list.
@node Explaining the Internals Reference
@section Explaining the Internals Reference
-
@menu
* Navigating the program reference::
* Layout interfaces::
Suppose we want to move the fingering indication in the fragment
below:
-@lilypond[quote,fragment,relative=2,verbatim]
+@lilypond[quote,relative=2,verbatim]
c-2
\stemUp
f
on @code{FingeringEvent} and one on @code{Fingering}.
The page on @code{FingeringEvent} describes the properties of the music
-expression for the input @code{-2}. The page contains many links
+expression for the input @w{@code{-2}}. The page contains many links
forward. For example, it says
@quotation
We have been talking of @emph{the} @code{Fingering} object, but actually it
does not amount to much. The initialization file (see
@rlearning{Other sources of information})
-@file{scm/@/define@/-grobs@/.scm} shows the soul of the @q{object},
+@file{scm/define-grobs.scm} shows the soul of the @q{object},
@example
(Fingering
(script-priority . 100)
(stencil . ,ly:text-interface::print)
(direction . ,ly:script-interface::calc-direction)
- (font-encoding . fetaNumber)
+ (font-encoding . fetaText)
(font-size . -5) ; don't overlap when next to heads.
(meta . ((class . Item)
(interfaces . (finger-interface
Recall that we wanted to change the position of the @b{2} in
-@lilypond[quote,fragment,relative=2,verbatim]
+@lilypond[quote,relative=2,verbatim]
c-2
\stemUp
f
Inserting this command before the Fingering object is created,
i.e., before @code{c2}, yields the following result:
-@lilypond[quote,relative=2,fragment,verbatim]
+@lilypond[quote,relative=2,verbatim]
\once \override Voice.Fingering #'padding = #3
c-2
\stemUp
Another thing that is needed, is an overview of the various naming
conventions:
- scheme functions: lowercase-with-hyphens (incl. one-word
+@itemize
+@item scheme functions: lowercase-with-hyphens (incl. one-word
names)
- scheme functions: ly:plus-scheme-style
- music events, music classes and music properties:
+@item scheme functions: ly:plus-scheme-style
+@item music events, music classes and music properties:
as-scheme-functions
- Grob interfaces: scheme-style
- backend properties: scheme-style (but X and Y!)
- contexts (and MusicExpressions and grobs): Capitalized or
+@item Grob interfaces: scheme-style
+@item backend properties: scheme-style (but X and Y!)
+@item contexts (and MusicExpressions and grobs): Capitalized or
CamelCase
- context properties: lowercaseFollowedByCamelCase
- engravers:
+@item context properties: lowercaseFollowedByCamelCase
+@item engravers:
Capitalized_followed_by_lowercase_and_with_underscores
+@end itemize
-Which of these are conventions and which are rules?
-Which are rules of the underlying language, and which are
+Questions to be answered:
+@itemize
+@item Which of these are conventions and which are rules?
+@item Which are rules of the underlying language, and which are
LP-specific?
-
+@end itemize
@node Modifying properties
@section Modifying properties
* The override command::
* The tweak command::
* set versus override::
+* Modifying alists::
@end menu
context. By changing these settings, the appearance of objects can be
altered.
+There are two different kinds of properties stored in contexts:
+context properties and grob properties. Context properties are
+properties that apply to the context as a whole and control
+how the context itself is displayed. In contrast, grob properties
+apply to specific grob types that will be displayed in the context.
+
+The @code{\set} and @code{\unset} commands are used to change values
+for context properties. The @code{\override} and @code{\revert}
+commands are used to change values for grob properties.
+
+@ignore
The syntax for this is
@example
applies to the current staff. Other staves will keep their normal
appearance. Here we see the command in action:
-@lilypond[quote,verbatim,relative=2,fragment]
+@lilypond[quote,verbatim,relative=2]
c4
\override Staff.Stem #'thickness = #4.0
c4
causing the default context @code{Voice} to be used. Adding
@code{\once} applies the change during one timestep only.
-@lilypond[quote,fragment,verbatim,relative=2]
+@lilypond[quote,verbatim,relative=2]
c4
\once \override Stem #'thickness = #4.0
c4
or beams, the @code{\override} command must be executed at the moment
when the object is created. In this example,
-@lilypond[quote,fragment,verbatim,relative=2]
+@lilypond[quote,verbatim,relative=2]
\override Slur #'thickness = #3.0
c8[( c
-\override Beam #'thickness = #0.6
+\override Beam #'beam-thickness = #0.6
c8 c])
@end lilypond
\override Stem #'(details beamed-lengths) = #'(4 4 3)
@end example
+@end ignore
@seealso
-Internals:
+Internals Reference:
+@rinternals{Backend},
+@rinternals{All layout objects},
@rinternals{OverrideProperty},
@rinternals{RevertProperty},
-@rinternals{PropertySet},
-@rinternals{Backend},
-@rinternals{All layout objects}.
-
+@rinternals{PropertySet}.
@knownissues
-
The back-end is not very strict in type-checking object properties.
Cyclic references in Scheme values for properties can cause hangs
or crashes, or both.
-
@node The set command
-@subsection The @code{\set} command
+@subsection The @code{@bs{}set} command
@cindex properties
@funindex \set
@cindex changing properties
-Each context can have different @emph{properties}, variables contained
-in that context. They can be changed during the interpretation step.
-This is achieved by inserting the @code{\set} command in the music,
+Each context has a set of @emph{properties}, variables contained
+in that context. Context properties are changed with the @code{\set}
+command, which has the following syntax:
@example
-\set @var{context}.@var{prop} = #@var{value}
+\set @var{context}.@var{property} = #@var{value}
@end example
-For example,
-@lilypond[quote,verbatim,relative=2,fragment]
+@var{value} is a Scheme object, which is why it must be preceded by
+the @code{#}@tie{}character.
+
+Contexts properties are usually named in
+@code{studlyCaps}. They mostly control the translation from
+music to notation, e.g. @code{localKeySignature} (for determining
+whether to print accidentals), or @code{measurePosition} (for
+determining when to print a bar line). Context properties can
+change value over time while interpreting a piece of music;
+@code{measurePosition} is an obvious example of
+this. Context properties are modified with @code{\set}.
+
+For example, multimeasure rests will be combined into a single bar
+if the context property @code{skipBars} is set to @code{#t}:
+
+@lilypond[quote,verbatim,relative=2]
R1*2
\set Score.skipBars = ##t
R1*2
@end lilypond
-This command skips measures that have no notes. The result is that
-multi-rests are condensed. The value assigned is a Scheme object. In
-this case, it is @code{#t}, the boolean True value.
+If the @var{context} argument is left out, then the property will be
+set in the current bottom context (typically @code{ChordNames},
+@code{Voice}, @code{TabVoice}, or @code{Lyrics}).
-If the @var{context} argument is left out, then the current bottom-most
-context (typically @code{ChordNames}, @code{Voice}, or
-@code{Lyrics}) is used. In this example,
-
-@lilypond[quote,verbatim,relative=2,fragment]
-c8 c c c
-\set autoBeaming = ##f
-c8 c c c
+@lilypond[quote,verbatim,relative=2]
+\set Score.autoBeaming = ##f
+<<
+ {
+ e8 e e e
+ \set autoBeaming = ##t
+ e8 e e e
+ } \\ {
+ c8 c c c c8 c c c
+ }
+>>
@end lilypond
-@noindent
-the @var{context} argument to @code{\set} is left out, so automatic
-beaming is switched off in the current @rinternals{Voice}. Note that
-the bottom-most context does not always contain the property that you
-wish to change -- for example, attempting to set the @code{skipBars}
-property (of the bottom-most context, in this case @code{Voice}) will
-have no effect.
-
-@lilypond[quote,verbatim,relative=2,fragment]
+The change is applied @q{on-the-fly}, during the music, so that the
+setting only affects the second group of eighth notes.
+
+Note that the bottom-most context does not always contain the property
+that you wish to change -- for example, attempting to set the
+@code{skipBars} property of the default bottom context, in this case
+@code{Voice}, will have no effect, because skipBars is a property of
+the @code{Score} context.
+
+@lilypond[quote,verbatim,relative=2]
R1*2
\set skipBars = ##t
R1*2
@end lilypond
-Contexts are hierarchical, so if a bigger context was specified, for
+Contexts are hierarchical, so if an enclosing context was specified, for
example @code{Staff}, then the change would also apply to all
-@code{Voice}s in the current stave. The change is applied
-@q{on-the-fly}, during the music, so that the setting only affects the
-second group of eighth notes.
+@code{Voice}s in the current staff.
@funindex \unset
-There is also an @code{\unset} command,
+The @code{\unset} command:
+
@example
-\unset @var{context}.@var{prop}
+\unset @var{context}.@var{property}
@end example
@noindent
-which removes the definition of @var{prop}. This command removes
-the definition only if it is set in @var{context}, so
+is used to remove the definition of @var{property} from
+@var{context}. This command removes
+the definition only if it is set in @var{context}.
+Properties that have been set in enclosing contexts will
+not be altered by an unset in an enclosed context:
+
+@lilypond[quote,verbatim,relative=2]
+\set Score.autoBeaming = ##t
+<<
+ {
+ \unset autoBeaming
+ e8 e e e
+ \unset Score.autoBeaming
+ e8 e e e
+ } \\ {
+ c8 c c c c8 c c c
+ }
+>>
+@end lilypond
+
+Like @code{\set}, the @var{context} argument does not have to be
+specified for a bottom context, so the two statements
@example
-\set Staff.autoBeaming = ##f
+\set Voice.autoBeaming = ##t
+\set autoBeaming = ##t
@end example
@noindent
-introduces a property setting at @code{Staff} level. The setting also
-applies to the current @code{Voice}. However,
+are equivalent if the current bottom context is @code{Voice}.
+
+
+@cindex \once
+Preceding a @code{\set} command by @code{\once} makes the
+setting apply to only a single time-step:
+
+@lilypond[quote,verbatim,relative=2]
+c4
+\once \set fontSize = #4.7
+c4
+c4
+@end lilypond
+
+A full description of all available context properties is in the
+internals reference, see
+@ifhtml
+@rinternals{Tunable context properties}.
+@end ifhtml
+@ifnothtml
+Translation @expansion{} Tunable context properties.
+@end ifnothtml
+
+@seealso
+Internals Reference:
+@rinternals{Tunable context properties}.
+
+@cindex grob properties
+@cindex properties, grob
+@funindex \override
+
+
+@node The override command
+@subsection The @code{\override} command
+
+There is a special type of context property: the grob
+description. Grob descriptions are named in @code{StudlyCaps}
+(starting with capital letters). They contain the
+@q{default settings} for a particular kind of grob as an
+association list. See @file{scm/define-grobs.scm}
+to see the settings for each grob description. Grob descriptions
+are modified with @code{\override}.
+
+@code{\override} is actually a shorthand;
@example
-\unset Voice.autoBeaming
+\override @var{context}.@var{GrobName} #'@var{property} = #@var{value}
@end example
@noindent
-does not have any effect. To cancel this setting, the @code{\unset}
-must be specified on the same level as the original @code{\set}. In
-other words, undoing the effect of @code{Staff.autoBeaming = ##f}
-requires
+is more or less equivalent to
+
+@c leave this long line -gp
@example
-\unset Staff.autoBeaming
+\set @var{context}.@var{GrobName} =
+ #(cons (cons '@var{property} @var{value})
+ <previous value of @var{context}.@var{GrobName}>)
@end example
-Like @code{\set}, the @var{context} argument does not have to be
-specified for a bottom context, so the two statements
+The value of @code{context}.@code{GrobName} (the alist) is used to initialize
+the properties of individual grobs. Grobs have
+properties, named in Scheme style, with
+@code{dashed-words}. The values of grob properties change
+during the formatting process: formatting basically amounts
+to computing properties using callback functions.
+
+For example, we can increase the thickness of a note stem by
+overriding the @code{thickness} property of the @code{Stem}
+object:
-@example
-\set Voice.autoBeaming = ##t
-\set autoBeaming = ##t
-@end example
+@lilypond[quote,verbatim,relative=2]
+c4 c
+\override Voice.Stem #'thickness = #3.0
+c4 c
+@end lilypond
-@noindent
-are equivalent.
+If no context is specified in an @code{\override}, the bottom
+context is used:
+
+@lilypond[quote,verbatim,relative=2]
+{ \override Staff.Stem #'thickness = #3.0
+ <<
+ {
+ e4 e
+ \override Stem #'thickness = #0.5
+ e4 e
+ } \\ {
+ c4 c c c
+ }
+ >>
+}
+@end lilypond
+@funindex \revert
+@cindex reverting overrides
+@cindex overrides, reverting
-@cindex \once
-Settings that should only apply to a single time-step can be entered
-with @code{\once}, for example in
+The effects of @code{\override} can be undone by @code{\revert}:
-@lilypond[quote,verbatim,relative=2,fragment]
-c4
-\once \set fontSize = #4.7
+@lilypond[quote,verbatim,relative=2]
c4
+\override Voice.Stem #'thickness = #3.0
+c4 c
+\revert Voice.Stem #'thickness
c4
@end lilypond
-the property @code{fontSize} is unset automatically after the second
-note.
+The effects of @code{\override} and @code{\revert} apply to all
+grobs in the affected context from the current time forward:
-A full description of all available context properties is in the
-program reference, see
-@ifhtml
-@rinternals{Tunable context properties}.
-@end ifhtml
-@ifnothtml
-Translation @expansion{} Tunable context properties.
-@end ifnothtml
+@lilypond[quote,verbatim,relative=2]
+{
+ <<
+ {
+ e4
+ \override Staff.Stem #'thickness = #3.0
+ e4 e e
+ } \\ {
+ c4 c c
+ \revert Staff.Stem #'thickness
+ c4
+ }
+ >>
+}
+@end lilypond
+@funindex \once
+@cindex overriding for only one moment
+@code{\once} can be used with @code{\override}
+to affect only the current time step:
-@node The override command
-@subsection The @code{\override} command
+@lilypond[quote,verbatim,relative=2]
+{
+ <<
+ {
+ \override Stem #'thickness = #3.0
+ e4 e e e
+ } \\ {
+ c4
+ \once \override Stem #'thickness = #3.0
+ c4 c c
+ }
+ >>
+}
+@end lilypond
+
+@ignore
Commands which change output generally look like
@example
@cindex internal documentation
For many properties, regardless of the data type of the property, setting the
-property to false ( @code{##f} ) will result in turning it off, causing
+property to false (@code{#f}) will result in turning it off, causing
LilyPond to ignore that property entirely. This is particularly useful for
turning off grob properties which may otherwise be causing problems.
We demonstrate how to glean this information from the notation manual
and the program reference.
+@end ignore
+
+@seealso
+Internals Reference:
+@rinternals{Backend}
@node The tweak command
@funindex \tweak
@cindex tweaking
+Changing grob properties
+with @code{\override} causes the changes to apply to all of the
+given grobs in the context at the moment the change applies.
+Sometimes, however, it is desirable to have changes apply to just
+one grob, rather than to all grobs in the affected context. This is
+accomplished with the @code{\tweak} command, which has the following
+syntax:
+
+@example
+\tweak @var{layout-object} #'@var{grob-property} @var{value}
+@end example
+
+Specifying @var{layout-object} is optional.
+The @code{\tweak} command applies to the music object that immediately
+follows @var{value} in the music stream.
+
+@ignore
In some cases, it is possible to take a short-cut for tuning
graphical objects. For objects that are created directly from
an item in the input file, you can use the @code{\tweak} command.
For example:
-@lilypond[relative=2,verbatim]
+@lilypond[relative=2,verbatim,quote]
< c
\tweak #'color #red
d
-^
@end lilypond
-@cindex chord, modifying one note in
+
But the main use of the @code{\tweak} command is to modify just
one of a number of notation elements which start at the same musical
moment, like the notes of a chord, or tuplet brackets which start
at the same time.
-For an introduction to the syntax and uses of the tweak command
-see @rlearning{Tweaking methods}.
-
The @code{\tweak} command sets a property in the following object
directly, without requiring the grob name or context to be
specified. For this to work, it is necessary for the @code{\tweak}
\tweak #'color #red c4
@end lilypond
+@end ignore
+
+For an introduction to the syntax and uses of the tweak command
+see @rlearning{Tweaking methods}.
+
When several similar items are placed at the same musical moment,
the @code{\override} command cannot be used to modify just one of
them -- this is where the @code{\tweak} command must be used.
@c TODO add examples of these
-@noindent
-and @code{\tweak} may be used to modify any single occurrence of
-these items.
+@cindex chord, modifying one note in
-Notably the @code{\tweak} command cannot be used to modify stems,
-beams or accidentals directly, since these are generated later by
-note heads, rather than by music elements in the input stream.
-Nor can a @code{\tweak} command be used to modify clefs or time
-signatures, since these become separated from any preceding
-@code{\tweak} command in the input stream by the automatic
-insertion of extra elements required to specify the context.
+In this example, the color of one note head and the type of another
+note head are modified within a single chord:
+
+@lilypond[relative=2,verbatim,quote]
+< c
+ \tweak #'color #red
+ d
+ g
+ \tweak #'duration-log #1
+ a
+> 4
+@end lilypond
-But the @code{\tweak} command can be used as an alternative to
-the @code{\override} command to modify those notational elements
-that do not cause any additional implicit elements to be added
-before them in the music stream. For example, slurs may be
-modified in this way:
+@code{\tweak} can be used to modify slurs:
@lilypond[verbatim,quote,relative=1]
c-\tweak #'thickness #5 ( d e f)
@end lilypond
-Also several @code{\tweak} commands may be placed before a
+
+For the @code{\tweak} command to work, it must
+remain immediately adjacent to the object to which it is
+to apply after the input file has been converted to a music stream.
+Tweaking a whole chord does not do anything since its music event
+only acts as a container, and all layout objects are created from events
+inside of the @code{EventChord}:
+
+@lilypond[relative=2,verbatim,quote]
+\tweak #'color #red c4
+\tweak #'color #red <c e>4
+<\tweak #'color #red c e>4
+@end lilypond
+
+The simple @code{\tweak} command cannot be used to modify any object
+that is not directly created from the input. In particular
+it will not affect stems, automatic
+beams or accidentals, since these are generated later by
+@code{NoteHead} layout objects rather than by music elements in the
+input stream.
+
+Such indirectly created layout objects can be tweaked using the explicit
+form of the @code{\tweak} command:
+
+@lilypond[relative=2,verbatim,quote]
+\tweak Stem #'color #red
+\tweak Beam #'color #green c8 e
+<c e \tweak Accidental #'font-size #-3 ges>4
+@end lilypond
+
+@code{\tweak} cannot be used to modify clefs or time
+signatures, since these become separated from any preceding
+@code{\tweak} command in the input stream by the automatic
+insertion of extra elements required to specify the context.
+
+Several @code{\tweak} commands may be placed before a
notational element -- all affect it:
@lilypond[verbatim,quote,relative=1]
The music stream which is generated from a section of an input file,
including any automatically inserted elements, may be examined,
-see @ref{Displaying music expressions}. This may be helpful in
-determining what may be modified by a @code{\tweak} command.
-
+see @rextend{Displaying music expressions}. This may be helpful in
+determining what may be modified by a @code{\tweak} command, or
+in determining how to adjust the input to make a @code{\tweak}
+apply.
@seealso
Learning Manual:
@rlearning{Tweaking methods}.
-Notation Reference:
-@ref{Displaying music expressions}.
-
+Extending LilyPond:
+@rextend{Displaying music expressions}.
@knownissues
-@cindex tweaks in a variable
-The @code{\tweak} command cannot be used inside a variable.
-
-@cindex tweaks in lyrics
-The @code{\tweak} commands cannot be used in @code{\lyricmode}.
-
@cindex tweaking control points
@cindex control points, tweaking
@node set versus override
@subsection @code{\set} vs. @code{\override}
+@c TODO -- This section is probably unnecessary now.
+
+@ignore
We have seen two methods of changing properties: @code{\set} and
@code{\override}. There are actually two different kinds of
properties.
-Contexts can have properties, which are usually named in
-@code{studlyCaps}. They mostly control the translation from
-music to notation, eg. @code{localKeySignature} (for determining
-whether to print accidentals), @code{measurePosition} (for
-determining when to print a bar line). Context properties can
-change value over time while interpreting a piece of music;
-@code{measurePosition} is an obvious example of
-this. Context properties are modified with @code{\set}.
+@code{fontSize} is a special property: it is equivalent to
+entering @code{\override ... #'font-size} for all pertinent
+objects. Since this is a common change, the special
+property (modified with @code{\set}) was created.
-There is a special type of context property: the element
-description. These properties are named in @code{StudlyCaps}
-(starting with capital letters). They contain the
-@q{default settings} for said graphical object as an
-association list. See @file{scm/@/define@/-grobs@/.scm}
-to see what kind of settings there are. Element descriptions
-may be modified with @code{\override}.
+@end ignore
-@code{\override} is actually a shorthand;
+
+@node Modifying alists
+@subsection Modifying alists
+
+Some user-configurable properties are internally represented as
+@emph{alists} (association lists), which store pairs of
+@emph{keys} and @emph{values}. The structure of an alist is:
@example
-\override @var{context}.@var{name} #'@var{property} = #@var{value}
+'((@var{key1} . @var{value1})
+ (@var{key2} . @var{value2})
+ (@var{key3} . @var{value3})
+ @dots{})
@end example
-@noindent
-is more or less equivalent to
+If an alist is a grob property or @code{\paper} variable, its keys
+can be modified individually without affecting other keys.
+
+For example, to reduce the space between adjacent staves in a
+staff-group, use the @code{staff-staff-spacing} property of the
+@code{StaffGrouper} grob. The property is an alist with four
+keys: @code{basic-distance}, @code{minimum-distance},
+@code{padding}, and @code{stretchability}. The standard settings
+for this property are listed in the @qq{Backend} section of the
+Internals Reference (see @rinternals{StaffGrouper}):
-@c leave this long line -gp
@example
-\set @var{context}.@var{name} #'@var{property} = #(cons (cons '@var{property} @var{value}) <previous value of @var{context})
+'((basic-distance . 9)
+ (minimum-distance . 7)
+ (padding . 1)
+ (stretchability . 5))
@end example
-The value of @code{context} (the alist) is used to initialize
-the properties of individual grobs. Grobs also have
-properties, named in Scheme style, with
-@code{dashed-words}. The values of grob properties change
-during the formatting process: formatting basically amounts
-to computing properties using callback functions.
+One way to bring the staves closer together is by reducing the
+value of the @code{basic-distance} key (@code{9}) to match the
+value of @code{minimum-distance} (@code{7}). To modify a single
+key individually, use a @emph{nested declaration}:
-@code{fontSize} is a special property: it is equivalent to
-entering @code{\override ... #'font-size} for all pertinent
-objects. Since this is a common change, the special
-property (modified with @code{\set}) was created.
+@lilypond[quote,verbatim]
+% default space between staves
+\new PianoStaff <<
+ \new Staff { \clef treble c''1 }
+ \new Staff { \clef bass c1 }
+>>
+
+% reduced space between staves
+\new PianoStaff \with {
+ % this is the nested declaration
+ \override StaffGrouper #'staff-staff-spacing #'basic-distance = #7
+} <<
+ \new Staff { \clef treble c''1 }
+ \new Staff { \clef bass c1 }
+>>
+@end lilypond
+
+Using a nested declaration will update the specified key (such as
+@code{basic-distance} in the above example) without altering any
+other keys already set for the same property.
+
+Now suppose we want the staves to be as close as possible without
+overlapping. The simplest way to do this is to set all four alist
+keys to zero. However, it is not necessary to enter four nested
+declarations, one for each key. Instead, the property can be
+completely re-defined with one declaration, as an alist:
+
+@lilypond[quote,verbatim]
+\new PianoStaff \with {
+ \override StaffGrouper #'staff-staff-spacing =
+ #'((basic-distance . 0)
+ (minimum-distance . 0)
+ (padding . 0)
+ (stretchability . 0))
+} <<
+ \new Staff { \clef treble c''1 }
+ \new Staff { \clef bass c1 }
+>>
+@end lilypond
+
+Note that any keys not explicitly listed in the alist definition
+will be reset to their @emph{default-when-unset} values. In the
+case of @code{staff-staff-spacing}, any unset key-values would be
+reset to zero (except @code{stretchability}, which takes the value
+of @code{basic-distance} when unset). Thus the following two
+declarations are equivalent:
+
+@example
+\override StaffGrouper #'staff-staff-spacing =
+ #'((basic-distance . 7))
+
+\override StaffGrouper #'staff-staff-spacing =
+ #'((basic-distance . 7)
+ (minimum-distance . 0)
+ (padding . 0)
+ (stretchability . 7))
+@end example
+
+One (possibly unintended) consequence of this is the removal of
+any standard settings that are set in an initialization file and
+loaded each time an input file is compiled. In the above example,
+the standard settings for @code{padding} and
+@code{minimum-distance} (defined in @file{scm/define-grobs.scm})
+are reset to their default-when-unset values (zero for both keys).
+Defining a property or variable as an alist (of any size) will
+always reset all unset key-values to their default-when-unset
+values. Unless this is the intended result, it is safer to update
+key-values individually with a nested declaration.
+
+@warning{Nested declarations will not work for context property
+alists (such as @code{beamExceptions}, @code{keySignature},
+@code{timeSignatureSettings}, etc.). These properties can only be
+modified by completely re-defining them as alists.}
@node Useful concepts and properties
@menu
* Input modes::
* Direction and placement::
-* Context layout order::
* Distances and measurements::
* Staff symbol properties::
* Spanners::
@item @code{\markup} commands
@item @code{\tag} commands
@item string markups, e.g. -"string"
-@item fingering instructions, e.g. @code{-1}
-@item articulation shortcuts, e.g. @code{-.}, @code{->}, @code{--}
+@item fingering instructions, e.g. @w{@code{-1}}
+@item articulation shortcuts, e.g. @w{@code{-.}}, @w{@code{->}}, @w{@code{--}}
@end itemize
Direction indicators affect only the next note:
@strong{The direction property}
-The position or direction of many layout objects is controlled
-by the @code{direction} property.
+The position or direction of many layout objects is controlled by the
+@code{direction} property.
-The value of the @code{direction} property may be
-set to @code{1}, meaning @qq{up} or @qq{above}, or to @code{-1},
-meaning @qq{down} or @qq{below}. The symbols @code{UP} and
-@code{DOWN} may be used instead of @code{1} and @code{-1}
-respectively. The default direction may be specified by setting
-@code{direction} to @code{0} or @code{CENTER}. Alternatively,
-in many cases predefined commands
-exist to specify the direction. These are all of the form
+The value of the @code{direction} property may be set to @code{1},
+meaning @qq{up} or @qq{above}, or to @w{@code{-1}}, meaning @qq{down} or
+@qq{below}. The symbols @code{UP} and @code{DOWN} may be used instead
+of @code{1} and @w{@code{-1}} respectively. The default direction may
+be specified by setting @code{direction} to @code{0} or @code{CENTER}.
+Alternatively, in many cases predefined commands exist to specify the
+direction. These are of the form
-@noindent
-@code{\xxxUp}, @code{xxxDown}, @code{xxxNeutral}
+@example
+@code{\xxxUp}, @code{\xxxDown} or @code{\xxxNeutral}
+@end example
@noindent
-where @code{xxxNeutral} means @qq{use the default direction}.
+where @code{\xxxNeutral} means @qq{use the default} direction.
See @rlearning{Within-staff objects}.
-In a few cases, arpeggio being the only common example, the value
-of the @code{direction} property specifies whether the object
-is to be placed to the right or left of the parent object. In
-this case @code{-1} or @code{LEFT} means @qq{to the left} and
-@code{1} or @code{RIGHT} means @qq{to the right}. @code{0}
-or @code{CENTER} means @qq{use the default} direction, as before.
+In a few cases, arpeggio for example, the value of the @code{direction}
+property can specify whether the object is to be placed to the right or
+left of the parent. In this case @w{@code{-1}} or @code{LEFT} means
+@qq{to the left} and @code{1} or @code{RIGHT} means @qq{to the right}.
+@code{0} or @code{CENTER} means @qq{use the default} direction.
@ignore
These all have side-axis set to #X
TrillPitchGroup - not tried
@end ignore
-These indications affect all notes until they are cancelled.
+These indications affect all notes until they are canceled.
@lilypond[verbatim,quote,relative=2]
c2( c)
c2( c)
@end lilypond
-
-@node Context layout order
-@subsection Context layout order
-
-@cindex contexts, layout order
-
-Contexts are normally positioned in a system from top to bottom
-in the order in which they are encountered in the input file. When
-contexts are nested, the outer context will include inner nested
-contexts as specified in the input file, provided the inner contexts
-are included in the outer context's @qq{accepts} list. Nested
-contexts which are not included in the outer context's @qq{accepts}
-list will be repositioned below the outer context rather than nested
-within it.
-
-Note that a context will be silently created implicitly if a command
-is encountered when there is no suitable context available to
-contain it. This can give rise to unexpected new staves or scores.
-
-The default order in which contexts are laid out and the
-@qq{accepts} list can be changed, see @ref{Aligning contexts}.
+In polyphonic music, it is generally better to specify an explicit
+@code{voice} than change an object's direction. For more information.
+See @ref{Multiple voices}.
@seealso
Learning Manual:
-@rprogram{An extra staff appears}.
+@rlearning{Within-staff objects}.
+
+Notation Reference:
+@ref{Multiple voices}.
@node Distances and measurements
other page layout details, and are by default specified in
millimeters. Distances may be specified in other units by
following the quantity by @code{\mm}, @code{\cm},
-@code{\in}@tie{}(inches), or @code{\pt}@tie{}(points, 1/72.27
-of an inch). Page layout distances can also be specified in
-scalable units (see the following paragraph) by appending
-@code{\staff-space} to the quantity.
-Page layout is described in detail in @ref{Page formatting}.
+@code{\in}@tie{}(inches), or @code{\pt}@tie{}(points, 1/72.27 of
+an inch). Page layout distances can also be specified in scalable
+units (see the following paragraph) by appending
+@code{\staff-space} to the quantity. Page layout is described in
+detail in @ref{Page layout}.
Scaled distances are always specified in units of the staff-space
or, rarely, the half staff-space. The staff-space is the distance
@code{staff-space}. For an explanation and an example of its use,
see @rlearning{Length and thickness of objects}.
-
@seealso
Learning Manual:
@rlearning{Length and thickness of objects}.
Notation Reference:
-@ref{Page formatting},
+@ref{Page layout},
@ref{Setting the staff size}.
their appearance and behaviour. Some of these properties are common
to all spanners; others are restricted to a sub-set of the spanners.
-All spanners support the @code{spanner-interface}. A few, esentially
+All spanners support the @code{spanner-interface}. A few, essentially
those that draw a straight line between the two objects, support in
addition the @code{line-spanner-interface}.
For some layout objects, the @code{minimum-length} property becomes
effective only if the @code{set-spacing-rods} procedure is called
explicitly. To do this, the @code{springs-and-rods} property should
-be set to @code{ly:spanner::set-spacing-rods}. For example,
+be set to @code{ly:spanner::set-spacing-rods}. For example,
the minimum length of a glissando has no effect unless the
@code{springs-and-rods} property is set:
@end lilypond
This property is not effective for all spanners. For example,
-seting it to @code{#t} has no effect on slurs or phrasing slurs
+setting it to @code{#t} has no effect on slurs or phrasing slurs
or on other spanners for which terminating on the bar line would
not be meaningful.
specified by the @code{left-broken} and @code{right-broken}
sub-lists of @code{bound-details}. For example:
-@lilypond[relative=2,ragged-right,verbatim,fragment]
+@lilypond[relative=2,ragged-right,verbatim,quote]
\override Glissando #'breakable = ##t
\override Glissando #'(bound-details right-broken Y) = #-3
c1 \glissando \break
@item attach-dir
This determines where the line starts and ends in the X-direction,
-relative to the bound object. So, a value of @code{-1} (or
+relative to the bound object. So, a value of @w{@code{-1}} (or
@code{LEFT}) makes the line start/end at the left side of the note
head it is attached to.
This is a markup that is evaluated to yield the stencil. It is used
to put @i{cresc.}, @i{tr} and other text on horizontal spanners.
-@lilypond[quote,ragged-right,fragment,relative=2,verbatim]
+@lilypond[quote,ragged-right,relative=2,verbatim]
\override TextSpanner #'(bound-details left text)
= \markup { \small \bold Slower }
c2\startTextSpan b c a\stopTextSpan
or @code{stencil-offset} will move the symbol at the edge vertically
relative to the end point of the line:
-@lilypond[relative=1,fragment,verbatim]
+@lilypond[relative=1,quote,verbatim]
\override TextSpanner
#'(bound-details left stencil-align-dir-y) = #-2
\override TextSpanner
@end lilypond
Note that negative values move the text @emph{up}, contrary to the
-effect that might be expected, as a value of @code{-1} or
+effect that might be expected, as a value of @w{@code{-1}} or
@code{DOWN} means align the @emph{bottom} edge of the text with
the spanner line. A value of @code{1} or @code{UP} aligns
the top edge of the text with the spanner line.
if @code{to-barline} is true and a bar line occurs before the next
note.
-@lilypond[verbatim,quote,ragged-right,relative=2,fragment]
+@lilypond[verbatim,quote,ragged-right,relative=2]
\endSpanners
c2 \startTextSpan c2 c2
\endSpanners
\startTextSpan with \stopTextSpan, nor is it necessary to close
hairpins with @code{\!}.
-
@seealso
Internals Reference:
@rinternals{TextSpanner},
value of @code{1}, is drawn after the staff lines (default
@code{layer} value @code{0}), so overwriting them. To change this,
the @code{Clef} object must be given in a lower value of
-@code{layer}, say @code{-1}, so that it is drawn earlier:
+@code{layer}, say @w{@code{-1}}, so that it is drawn earlier:
@lilypond[quote,verbatim,relative=2]
\override Staff.Clef #'color = #white
where there is no line break, or after a line break.
Alternatively, these eight combinations may be specified
-by pre-defined functions, defined in @file{scm/@/output@/-lib@/.scm},
+by pre-defined functions, defined in @file{scm/output-lib.scm},
where the last three columns indicate whether the layout objects
will be visible in the positions shown at the head of the columns:
-@multitable {@code{begin-of-line-invisible}} {@code{'#(#t #t #t)}} {yes} {yes} {yes}
+@multitable {@code{begin-of-line-invisible}} {@code{'#(#t #t #t)}} {Before} {At no} {After}
@headitem Function @tab Vector @tab Before @tab At no @tab After
@headitem form @tab form @tab break @tab break @tab break
@end multitable
The example below shows the use of the vector form to control the
-visibility of barlines:
+visibility of bar lines:
@lilypond[quote,verbatim,relative=1,ragged-right]
f4 g a b
@cindex clefs, visibility of octavation
The small octavation symbol on octavated clefs is produced by the
-@code{OctavateEight} layout object. Its visibility is controlled
-independently from that of the @code{Clef} object, so it is
-necessary to apply any required @code{break-visibility} overrides
-to both the @code{Clef} and the @code{OctavateEight} layout objects
-to fully suppress such clef symbols at the start of each line.
+@code{OctavateEight} layout object. Its visibility is automatically
+inherited from the @code{Clef} object, so it is not necessary to apply
+any required @code{break-visibility} overrides to the @code{OctavateEight}
+layout objects to suppress octavation symbols for invisible clefs.
For explicit clef changes, the @code{explicitClefVisibility}
property controls both the clef symbol and any octavation symbol
associated with it.
-
@seealso
Learning Manual:
-@rlearning{Visibility and color of objects}
+@rlearning{Visibility and color of objects}.
@node Line styles
Here is an example showing the different line styles available,
and how to tune them.
-@lilypond[relative=2,ragged-right,verbatim,fragment]
+@lilypond[relative=2,ragged-right,verbatim,quote]
d2 \glissando d'2
\once \override Glissando #'style = #'dashed-line
d,2 \glissando d'2
on-the-fly for every graphic object, but it is possible to
override these:
-@c FIXME Complete
-@lilypond[relative=2,ragged-right,verbatim,fragment]
+@c TODO Complete
+@lilypond[relative=2,ragged-right,verbatim,quote]
e2 \glissando f
\once \override Glissando #'(bound-details right Y) = #-2
e2 \glissando f
@end lilypond
-The value for @code{Y} is set to @code{-2} for the right end
+The value for @code{Y} is set to @w{@code{-2}} for the right end
point. The left side may be similarly adjusted by specifying
@code{left} instead of @code{right}.
* Vertical grouping of grobs::
* Modifying stencils::
* Modifying shapes::
+* Unpure-pure containers::
@end menu
-
@seealso
Learning Manual:
@rlearning{Tweaking output},
Notation Reference:
@ref{Explaining the Internals Reference},
-@ref{Modifying properties},
-@ref{Interfaces for programmers}.
+@ref{Modifying properties}.
+
+Extending LilyPond:
+@rextend{Interfaces for programmers}.
Installed Files:
-@file{scm/@/define@/-grobs@/.scm}.
+@file{scm/define-grobs.scm}.
Snippets:
@rlsr{Tweaks and overrides}.
@node Aligning objects
@subsection Aligning objects
-Graphical objects which support the @code{self-alignment-interface} and/or
-the @code{side-position-interface} can be
-aligned to a previously placed object in a variety of ways. For a list of these objects, see
+Graphical objects which support the @code{self-alignment-interface}
+and/or the @code{side-position-interface} can be aligned to a previously
+placed object in a variety of ways. For a list of these objects, see
@rinternals{self-alignment-interface} and @rinternals{side-position-interface}.
All graphical objects have a reference point, a horizontal extent and a
vertical extent. The horizontal extent is a pair of numbers
giving the displacements from the reference point of the left and
-right edges, displacements to the left being negative. The
-vertical extent is a pair of numbers giving the displacement from
-the reference point to the bottom and top edges, displacements down
-being negative.
+right edges, displacements to the left being negative. The vertical
+extent is a pair of numbers giving the displacement from the reference
+point to the bottom and top edges, displacements down being negative.
An object's position on a staff is given by the values of the
@code{X-offset} and @code{Y-offset} properties. The value of
-@code{X-offset} gives the displacement from the x coordinate of
+@code{X-offset} gives the displacement from the X coordinate of
the reference point of the parent object, and the value of
@code{Y-offset} gives the displacement from the center line of the
-staff. The values of @code{X-offset} and
-@code{Y-offset} may be set directly or may be set to be calculated
-by procedures in order to achieve alignment with the parent object
-in several ways.
+staff. The values of @code{X-offset} and @code{Y-offset} may
+be set directly or may be set to be calculated by procedures in order
+to achieve alignment with the parent object.
@warning{Many objects have special positioning considerations which
cause any setting of @code{X-offset} or @code{Y-offset} to be
ignored or modified, even though the object supports the
-@code{self-alignment-interface}.}
+@code{self-alignment-interface}. Overriding the @code{X-offset}
+or @code{Y-offset} properties to a fixed value causes the respective
+@code{self-alignment} property to be disregarded.}
+
+For example, an accidental can be repositioned vertically by setting
+@code{Y-offset} but any changes to @code{X-offset} have no effect.
+
+Rehearsal marks may be aligned with breakable objects such as bar
+lines, clef symbols, time signature symbols and key signatures. There
+are special properties to be found in the @code{break-aligned-interface}
+for positioning rehearsal marks on such objects.
-For example, an accidental can be repositioned
-vertically by setting @code{Y-offset} but any changes to
-@code{X-offset} have no effect.
+@seealso
+Notation Reference:
+@ref{Using the break-alignable-interface}.
-Rehearsal marks may be aligned with
-breakable objects such as bar lines, clef symbols, time signature
-symbols and key signatures. There are special properties to be
-found in the @code{break-aligned-interface} for positioning rehearsal
-marks on such objects.
+Extending LilyPond:
+@rextend{Callback functions}.
@menu
-* Setting @code{X-offset} and @code{Y-offset} directly::
-* Using the @code{side-position-interface}::
-* Using the @code{self-alignment-interface}::
-* Using the @code{break-alignable-interface}::
+* Setting X-offset and Y-offset directly::
+* Using the side-position-interface::
+* Using the self-alignment-interface::
+* Using the break-alignable-interface::
@end menu
-@node Setting @code{X-offset} and @code{Y-offset} directly
+@node Setting X-offset and Y-offset directly
@unnumberedsubsubsec Setting @code{X-offset} and @code{Y-offset} directly
Numerical values may be given to the @code{X-offset} and @code{Y-offset}
@c TODO write more
-@node Using the @code{side-position-interface}
+@node Using the side-position-interface
@unnumberedsubsubsec Using the @code{side-position-interface}
An object which supports the @code{side-position-interface} can be
@c TODO Add examples
-@node Using the @code{self-alignment-interface}
+@node Using the self-alignment-interface
@unnumberedsubsubsec Using the @code{self-alignment-interface}
@emph{Self-aligning objects horizontally}
real value, in units of half the total X extent of the
object. Negative values move the object to the right, positive
to the left. A value of @code{0} centers the object on the
-reference point of its parent, a value of @code{-1} aligns the
+reference point of its parent, a value of @w{@code{-1}} aligns the
left edge of the object on the reference point of its parent,
and a value of @code{1} aligns the right edge of the object on the
reference point of its parent. The symbols @code{LEFT},
-@code{CENTER} and @code{RIGHT} may be used instead of the values
-@code{-1, 0, 1} respectively.
+@code{CENTER}, and @code{RIGHT} may be used instead of the values
+@w{@code{-1}}, @code{0}, and @code{1}, respectively.
Normally the @code{\override} command would be used to modify the
value of @code{self-alignment-X}, but the @code{\tweak} command
This may make adjusting the value of some objects tricky.
The units are just half the vertical extent of the object, which
is usually quite small, so quite large numbers may be required.
-A value of @code{-1} aligns the lower edge of the object with
+A value of @w{@code{-1}} aligns the lower edge of the object with
the reference point of the parent object, a value of @code{0}
aligns the center of the object with the reference point of the
parent, and a value of @code{1} aligns the top edge of the object
with the reference point of the parent. The symbols @code{DOWN},
-@code{CENTER}, @code{UP} may be substituted for @code{-1, 0, 1}
-respectively.
+@code{CENTER}, and @code{UP} may be substituted for @w{@code{-1}},
+@code{0}, and @code{1}, respectively.
@emph{Self-aligning objects in both directions}
@c TODO The align-interface, BassFigureAlignment and VerticalAlignment
-@node Using the @code{break-alignable-interface}
+@node Using the break-alignable-interface
@unnumberedsubsubsec Using the @code{break-alignable-interface}
@cindex align to objects
centered above the object:
@lilypond[verbatim,quote,relative=1]
-e1
-% the RehearsalMark will be centered above the Clef
+% The rehearsal mark will be centered above the Clef
\override Score.RehearsalMark #'break-align-symbols = #'(clef)
\key a \major
\clef treble
\mark "↓"
-e
-% the RehearsalMark will be centered above the TimeSignature
+e1
+% The rehearsal mark will be centered above the Time Signature
\override Score.RehearsalMark #'break-align-symbols = #'(time-signature)
\key a \major
\clef treble
\time 3/4
\mark "↓"
e2.
+% The rehearsal mark will be centered above the Breath Mark
+\override Score.RehearsalMark #'break-align-symbols = #'(breathing-sign)
+\key a \major
+\clef treble
+\time 4/4
+e1
+\breathe
+\mark "↓"
@end lilypond
A list of possible target alignment objects may be specified. If
line would be.
@lilypond[verbatim,quote,relative=1]
-e1
-% the RehearsalMark will be centered above the Key Signature
+% The rehearsal mark will be centered above the Key Signature
\override Score.RehearsalMark #'break-align-symbols = #'(key-signature clef)
\key a \major
\clef treble
\mark "↓"
-e
-% the RehearsalMark will be centered above the Clef
+e1
+% The rehearsal mark will be centered above the Clef
\set Staff.explicitKeySignatureVisibility = #all-invisible
\override Score.RehearsalMark #'break-align-symbols = #'(key-signature clef)
-\key a \minor
+\key a \major
\clef bass
\mark "↓"
-e,
+gis,,1
+% The rehearsal mark will be centered above the Bar Line
+\set Staff.explicitKeySignatureVisibility = #all-invisible
+\set Staff.explicitClefVisibility = #all-invisible
+\override Score.RehearsalMark #'break-align-symbols = #'(key-signature clef)
+\key a \major
+\clef treble
+\mark "↓"
+e''1
@end lilypond
The alignment of the rehearsal mark relative to the notation object
multiple staves, this setting should be done for all the staves.
@lilypond[verbatim,quote,relative=1]
-% The RehearsalMark will be centered above the KeySignature
+% The RehearsalMark will be centered above the Key Signature
\override Score.RehearsalMark #'break-align-symbols = #'(key-signature)
\key a \major
\clef treble
\time 4/4
\mark "↓"
e1
-% The RehearsalMark will be aligned with the left edge of the KeySignature
+% The RehearsalMark will be aligned with the left edge of the Key Signature
\once \override Score.KeySignature #'break-align-anchor-alignment = #LEFT
\mark "↓"
\key a \major
-e
-% The RehearsalMark will be aligned with the right edge of the KeySignature
+e1
+% The RehearsalMark will be aligned with the right edge of the Key Signature
\once \override Score.KeySignature #'break-align-anchor-alignment = #RIGHT
\key a \major
\mark "↓"
-e
+e1
@end lilypond
-The rehearsal mark can also be offset to the right or left of the left edge
-by an arbitrary amount. The units are staff-spaces:
+The rehearsal mark can also be offset to the right or left of the left
+edge by an arbitrary amount. The units are staff-spaces:
@lilypond[verbatim,quote,relative=1]
-% The RehearsalMark will be aligned with the left edge of the KeySignature
+% The RehearsalMark will be aligned with the left edge of the Key Signature
% and then shifted right by 3.5 staff-spaces
\override Score.RehearsalMark #'break-align-symbols = #'(key-signature)
\once \override Score.KeySignature #'break-align-anchor = #3.5
\key a \major
\mark "↓"
-e
-% The RehearsalMark will be aligned with the left edge of the KeySignature
+e1
+% The RehearsalMark will be aligned with the left edge of the Key Signature
% and then shifted left by 2 staff-spaces
\once \override Score.KeySignature #'break-align-anchor = #-2
\key a \major
\mark "↓"
-e
+e1
@end lilypond
@node Vertical grouping of grobs
@subsection Vertical grouping of grobs
-@c FIXME Expand this section
+@c TODO Expand this section
The VerticalAlignment and VerticalAxisGroup grobs work together.
VerticalAxisGroup groups together different grobs like Staff, Lyrics,
@c TODO Add inserting Postscript or ref to later
-
@seealso
Notation Reference:
@ref{Graphic notation inside markup},
@cindex slurs, modifying
@cindex ties, modifying
-@cindex Bézier curves
-@cindex Bézier control points
+@cindex Bézier curves, control points
+@cindex control points, Bézier curves
Ties, slurs and phrasing slurs are drawn as third-order Bézier
curves. If the shape of the tie or slur which is calculated
@lilypond[verbatim,quote,relative=1]
<<
- { e1 ~ e }
+ { e1~ e }
\\
{ r4 <g c,> <g c,> <g c,> }
>>
{
\once \override Tie
#'control-points = #'((1 . -1) (3 . 0.6) (12.5 . 0.6) (14.5 . -1))
- e1 ~ e1
+ e1 ~ e
}
\\
- { r4 <g c,> <g c,> <g c,>4 }
+ { r4 <g c,> <g c,> <g c,> }
>>
@end lilypond
@knownissues
-
It is not possible to modify shapes of ties or slurs by changing
-the @code{control-points} property if there are more than one at
-the same musical moment, not even by using the @code{\tweak}
-command.
+the @code{control-points} property if there are multiple ties or slurs
+at the same musical moment -- the @code{\tweak} command will also not
+work in this case. However, the @code{tie-configuration} property of
+@code{TieColumn} can be overridden to set start line and direction as
+required.
+
+@seealso
+Internals Reference:
+@rinternals{TieColumn}.
+
+@cindex Scheme, pure containers
+@cindex Scheme, unpure containers
+@cindex pure containers, Scheme
+@cindex unpure containers, Scheme
+@cindex horizontal spacing, overriding
+
+
+@node Unpure-pure containers
+@subsection Unpure-pure containers
+
+Unpure-pure containers are useful for overriding @emph{Y-axis} spacing
+calculations - specifically @code{Y-offset} and @code{Y-extent} - with a
+Scheme function instead of a literal (i.e. a number or pair).
+
+For certain grobs, the @code{Y-extent} is based on the @code{stencil}
+property, overriding the stencil property of one of these will
+require an additional @code{Y-extent} override with an unpure-pure
+container. When a function overrides a @code{Y-offset} and/or
+@code{Y-extent} it is assumed that this will trigger line breaking
+calculations too early during compilation. So the function is not
+evaluated at all (usually returning a value of @samp{0} or
+@samp{'(0 . 0)}) which can result in collisions. A @q{pure} function
+will not affect properties, objects or grob suicides and therefore will
+always have its Y-axis-related evaluated correctly.
+
+Currently, there are about thirty functions that are already considered
+@q{pure} and Unpure-pure containers are a way to set functions not on
+this list as @q{pure}. The @q{pure} function is evaluated @emph{before}
+any line-breaking and so the horizontal spacing can be adjusted
+@q{in time}. The @q{unpure} function is then evaluated @emph{after}
+line breaking.
+
+@warning{As it is difficult to always know which functions are on this
+list we recommend that any @q{pure} functions you create do not use
+@code{Beam} or @code{VerticalAlignment} grobs.}
+
+An unpure-pure container is constructed as follows;
+
+@code{(ly:make-unpure-pure-container f0 f1)}
+
+where @code{f0} is a function taking @var{n} arguments (@var{n >= 1})
+and the first argument must always be the grob. This is the function
+that gives the actual result. @var{f1} is the function being labeled
+as @q{pure} that takes @var{n + 2} arguments. Again, the first argument
+must always still be the grob but the second and third are @q{start}
+and @q{end} arguments.
+
+@var{start} and @var{end} are, for all intents and purposes, dummy
+values that only matter for @code{Spanners} (i.e @code{Hairpin} or
+@code{Beam}), that can return different height estimations based on a
+starting and ending column.
+
+The rest are the other arguments to the first function (which
+may be none if @var{n = 1}).
+
+The results of the second function are used as an approximation of the
+value needed which is then used by the first function to get the real
+value which is then used for fine-tuning much later during the spacing
+process.
+
+@lilypond[verbatim,quote,ragged-right]
+#(define (square-line-circle-space grob)
+(let* ((pitch (ly:event-property (ly:grob-property grob 'cause) 'pitch))
+ (notename (ly:pitch-notename pitch)))
+ (if (= 0 (modulo notename 2))
+ (make-circle-stencil 0.5 0.0 #t)
+ (make-filled-box-stencil '(0 . 1.0)
+ '(-0.5 . 0.5)))))
+
+squareLineCircleSpace = {
+ \override NoteHead #'stencil = #square-line-circle-space
+}
+
+smartSquareLineCircleSpace = {
+ \squareLineCircleSpace
+ \override NoteHead #'Y-extent =
+ #(ly:make-unpure-pure-container
+ ly:grob::stencil-height
+ (lambda (grob start end) (ly:grob::stencil-height grob)))
+}
+
+\new Voice \with { \remove "Stem_engraver" }
+\relative c'' {
+ \squareLineCircleSpace
+ cis4 ces cisis c
+ \smartSquareLineCircleSpace
+ cis4 ces cisis c
+}
+@end lilypond
+
+In the first measure, without the unpure-pure container, the spacing
+engine does not know the width of the note head and lets it collide with
+the accidentals. In the second measure, with unpure-pure containers,
+the spacing engine knows the width of the note heads and avoids the
+collision by lengthening the line accordingly.
+
+Usually for simple calculations nearly-identical functions for both the
+@q{unpure} and @q{pure} parts can be used, by only changing the number
+of arguments passed to, and the scope of, the function.
+
+@warning{If a function is labeled as @q{pure} and it turns out not to
+be, the results can be unexpected.}
+
+
+@node Using music functions
+@section Using music functions
+
+@c TODO -- add @seealso, etc. to these subsections
+Where tweaks need to be reused with different music expressions,
+it is often convenient to make the tweak part of a @emph{music
+function}. In this section, we discuss only @emph{substitution}
+functions, where the object is to substitute a variable into a
+piece of LilyPond input code. Other more complex functions are
+described in @rextend{Music functions}.
+@menu
+* Substitution function syntax::
+* Substitution function examples::
+@end menu
+
+@node Substitution function syntax
+@subsection Substitution function syntax
+
+Making a function that substitutes a variable into LilyPond
+code is easy. The general form of these functions is
+
+@example
+function =
+#(define-music-function
+ (parser location @var{arg1} @var{arg2} @dots{})
+ (@var{type1?} @var{type2?} @dots{})
+ #@{
+ @var{@dots{}music@dots{}}
+ #@})
+@end example
+
+@noindent
+where
+
+@multitable @columnfractions .33 .66
+@item @code{@var{argN}}
+@tab @var{n}th argument
+
+@item @code{@var{typeN?}}
+@tab a scheme @emph{type predicate} for which @code{@var{argN}}
+must return @code{#t}.
+
+@item @code{@var{@dots{}music@dots{}}}
+@tab normal LilyPond input, using @code{$} (in places where only
+Lilypond constructs are allowed) or @code{#} (to use it as a Scheme
+value or music function argument or music inside of music lists) to
+reference arguments
+(eg. @samp{#arg1}).
+@end multitable
+
+The @code{parser} and @code{location} arguments are mandatory, and
+are used in some advanced situations as described in the
+@q{Extending} manual (see @rextend{Music functions}). For
+substitution functions, just be sure to include them.
+
+The list of type predicates is also required. Some of the most
+common type predicates used in music functions are:
+
+@example
+boolean?
+cheap-list? @emph{(use instead of }@q{list?}@emph{ for faster processing)}
+ly:duration?
+ly:music?
+ly:pitch?
+markup?
+number?
+pair?
+string?
+symbol?
+@end example
+
+@noindent
+For a list of available type predicates, see
+@ref{Predefined type predicates}. User-defined type predicates
+are also allowed.
+
+@seealso
+Notation Reference:
+@ref{Predefined type predicates}.
+
+Extending Lilypond:
+@rextend{Music functions}.
+
+Installed Files:
+@file{lily/music-scheme.cc},
+@file{scm/c++.scm},
+@file{scm/lily.scm}.
+
+
+@node Substitution function examples
+@subsection Substitution function examples
+
+This section introduces some substitution function examples.
+These are not intended to be exhaustive, but rather to demonstrate
+some of the possibilities of simple substitution functions.
+
+In the first example, a function is defined that simplifies
+setting the padding of a TextScript:
+
+@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
+
+In addition to numbers, we can use music expressions such
+as notes for arguments to music functions:
+
+@lilypond[quote,verbatim,ragged-right]
+custosNote =
+#(define-music-function
+ (parser location note)
+ (ly:music?)
+ #{
+ \tweak NoteHead #'stencil #ly:text-interface::print
+ \tweak NoteHead #'text
+ \markup \musicglyph #"custodes.mensural.u0"
+ \tweak Stem #'stencil ##f
+ #note
+ #})
+
+\relative c' { c4 d e f \custosNote g }
+@end lilypond
+
+Substitution functions with multiple arguments can be defined:
+@lilypond[quote,verbatim,ragged-right]
+tempoPadded =
+#(define-music-function
+ (parser location padding tempotext)
+ (number? markup?)
+ #{
+ \once \override Score.MetronomeMark #'padding = #padding
+ \tempo \markup { \bold #tempotext }
+ #})
+
+\relative c'' {
+ \tempo \markup { "Low tempo" }
+ c4 d e f g1
+ \tempoPadded #4.0 "High tempo"
+ g4 f e d c1
+}
+@end lilypond
+@c TODO: add appropriate @@ref's here.
projects / lilypond.git / blobdiff