@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 "2.11.38"
+
@node Changing defaults
@chapter Changing defaults
The purpose of LilyPond's design is to provide the finest output
quality as a default. Nevertheless, it may happen that you need to
change this default layout. The layout is controlled through a large
-number of proverbial ``knobs and switches.'' This chapter does not
+number of proverbial @q{knobs and switches.} This chapter does not
list each and every knob. Rather, it outlines what groups of controls
are available and explains how to lookup which knob to use for a
particular effect.
-@cindex Program reference
+@cindex Internals Reference
The controls available for tuning are described in a separate
document, the
@iftex
-Program reference
+Internals Reference manual.
@end iftex
@ifnottex
-@ref{Top,Program reference,,lilypond-internals}.
+@ref{Top,Internals Reference,,lilypond-internals}.
@end ifnottex
-manual. That manual
+That manual
lists all different variables, functions and options available in
LilyPond. It is written as a HTML document, which is available
-@uref{http://@/lilypond@/.org/@/doc/@/v2.5/@/Documentation/@/user/@/out@/-www/@/lilypond@/-internals/,on@/-line},
+@c leave the @uref as one long line.
+@uref{http://@/lilypond@/.org/@/doc/@/stable/@/Documentation/@/user/@/lilypond@/-internals/,on@/-line},
but is also included with the LilyPond documentation package.
-There are three areas where the default settings may be changed:
+There are four areas where the default settings may be changed:
+
+@itemize
+@item
+Automatic notation: changing the automatic creation of notation
+elements. For example, changing the beaming rules.
-@itemize @bullet
@item
Output: changing the appearance of individual
objects. For example, changing stem directions or the location of
subscripts.
-
+
@item
Context: changing aspects of the translation from music events to
-notation. For example, giving each staff a separate time signature.
-
+notation. For example, giving each staff a separate time signature.
+
@item
-Global layout: changing the appearance of the spacing, line
-breaks, and page dimensions.
+Page layout: changing the appearance of the spacing, line
+breaks, and page dimensions. These modifications are discussed
+in @ref{Non-musical notation}, and @ref{Spacing issues}.
@end itemize
-Then there are separate systems for typesetting text (like
-@emph{ritardando}) and selecting different fonts. This chapter also
-discusses these.
-
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{@ref{Scheme tutorial} contains a short tutorial
+@code{#}.@footnote{@rlearning{Scheme tutorial}, contains a short tutorial
on entering numbers, lists, strings, and symbols in Scheme.}
@menu
* Interpretation contexts::
-* The \override command::
+* Explaining the Internals Reference::
+* Modifying properties::
+* Common properties::
+* Advanced tweaks::
+* old The \override command::
+* Discussion of specific tweaks::
@end menu
-
+
@node Interpretation contexts
@section Interpretation contexts
-When music is printed, a lot of notational elements must be added to the
-input, which is often bare bones. For example, compare the input and
-output of the following example:
-
-@lilypond[quote,verbatim,relative=2,fragment]
-cis4 cis2. g4
-@end lilypond
-
-The input is rather sparse, but in the output, bar lines, accidentals,
-clef, and time signature are added. LilyPond @emph{interprets} the
-input. During this step, the musical information is inspected in time
-order, similar to reading a score from left to right. While reading,
-the input, the program remembers where measure boundaries are, and what
-pitches need explicit accidentals. This information can be presented on
-several levels. For example, the effect of an accidental is limited
-to a single staff, while a bar line must be synchronized across the
-entire score.
-
-Within LilyPond, these rules and bits of information are grouped in
-so-called Contexts. Examples of context are @context{Voice},
-@context{Staff}, and @context{Score}. They are hierarchical, for
-example, a @context{Staff} can contain many @context{Voice}s, and a
-@context{Score} can contain many @context{Staff} contexts.
-
-Each context has the responsibility for enforcing some notation rules,
-creating some notation objects and maintaining the associated
-properties. So, the synchronization of bar lines is handled at
-@context{Score} context. The @context{Voice} may introduce an
-accidental and then the @context{Staff} context maintains the rule to
-show or suppress the accidental for the remainder of the measure.
-
-For simple scores, contexts are created implicitly, and you need not
-be aware of them. For larger pieces, such as piano music, they must be
-created explicitly to make sure that you get as many staves as you
-need, and that they are in the correct order. For typesetting pieces
-with specialized notation, it can be useful to modify existing or
-to define new contexts.
-
-
-A complete description of all available contexts is in the program
-reference, see
-@ifhtml
-@internalsref{Contexts}.
-@end ifhtml
-@ifnothtml
-Translation @arrow{} Context.
-@end ifnothtml
-
-@c [TODO: describe propagation]
-
+This section describes what contexts are, and how to modify them.
@menu
+* Contexts explained::
* Creating contexts::
-* Changing context properties on the fly::
* Modifying context plug-ins::
-* Layout tunings within contexts::
* Changing context default settings::
* Defining new contexts::
+* Aligning contexts::
@end menu
+
+@node Contexts explained
+@subsection Contexts explained
+
+>> > > - list of contexts: my *danger unmaintainable*
+>> > > alarm just went off. I'm
+
+I knew it would... And leaving out some of them is perfectly fine
+with me.
+I do think that a list like this, with the main contexts and a
+brief
+description of what they do (perhaps also with a note about what
+default
+behavior is associated with each of them, but this may be
+unmanageable),
+should be there, and then we could simply list the remaining ones
+without
+further explanation and with links to the IR.
+
+
+The Master Of All Contexts
+==========================
+
+ * Score
+ This is the top level notation context. No other context
+can
+ contain a Score context. This context handles the
+ administration of time signatures. It also makes sure that
+ items such as clefs, time signatures, and key-signatures
+are
+ aligned across staves.
+ You cannot explicitly instantiate a Score context (since
+it is
+ not contained in any other context). It is instantiated
+ automatically when an output definition (a \score or
+\layout
+ block) is processed.
+ (it should also be made clear somewhere what the
+difference is between
+ \score and \Score).
+
+Top-level contexts: Staff containers
+====================================
+ * StaffGroup
+ Groups staves while adding a bracket on the left side,
+ grouping the staves together. The bar lines of the
+contained
+ staves are connected vertically. StaffGroup only consists
+of a
+ collection of staves, with a bracket in front and spanning
+bar
+ lines.
+ * ChoirStaff
+ Identical to StaffGroup except that the contained staves
+are
+ not connected vertically.
+ * GrandStaff
+ A group of staves, with a brace on the left side, grouping
+the
+ staves together. The bar lines of the contained staves are
+ connected vertically.
+ * PianoStaff
+ Just like GrandStaff but with a forced distance between
+the
+ staves, so cross staff beaming and slurring can be used.
+ * DrumStaff
+ Handles typesetting for percussion. Can contain DrumVoice
+ * InnerStaffGroup
+ * InnerChoirStaff
+
+Staff-level contexts
+====================
+ * Staff
+ Handles clefs, bar lines, keys, accidentals. It can
+contain
+ Voice contexts.
+ * RhythmicStaff
+ Like Staff but for printing rhythms. Pitches are
+ ignored; the notes are printed on one line.
+ * TabStaff
+ Context for generating tablature. By default lays the
+music
+ expression out as a guitar tablature, printed on six
+lines.
+ * VaticanaStaff
+ Same as Staff, except that it is accommodated for
+ typesetting a piece in gregorian style.
+ * MensuralStaff
+ Same as Staff, except that it is accommodated for
+ typesetting a piece in mensural style.
+
+Voice-level (bottom) contexts
+=============================
+What is generated by default here? The voice-level contexts
+initiate
+certain properties and start engravers.
+
+ * Voice
+ Corresponds to a voice on a staff. This context handles
+the
+ conversion of dynamic signs, stems, beams, super- and
+ subscripts, slurs, ties, and rests.
+ You have to instantiate this explicitly if you want to
+have
+ multiple voices on the same staff.
+ Bottom context.
+ * VaticanaVoice
+ Same as Voice, except that it is accommodated for
+ typesetting a piece in gregorian style.
+ * MensuralVoice
+ Same as Voice, except that it is accommodated for
+ typesetting a piece in mensural style.
+ * Lyrics
+ Corresponds to a voice with lyrics. Handles the printing
+of a
+ single line of lyrics.
+ Bottom context.
+ * DrumVoice
+ A voice on a percussion staff.
+ * FiguredBass
+
+ * ChordNames
+ Typesets chord names. This context is a `bottom' context;
+it
+ cannot contain other contexts.
+
+------------------------------
+Then the following, which I don't know what to do with:
+
+ * TabVoice
+ * GregorianTranscriptionVoice
+ * GregorianTranscriptionStaff
+
+ * FretBoards
+ Engraves fretboards from chords. Not easy... Not
+documented.
+ * NoteNames
+
+ * CueVoice Not documented
+ * Global
+ Hard coded entry point for LilyPond. Cannot be tuned.
+ * Devnull
+ Silently discards all musical information given to this
+context.
+
+
+
@node Creating contexts
@subsection Creating contexts
-For scores with only one voice and one staff, correct contexts are
+For scores with only one voice and one staff, contexts are
created automatically. For more complex scores, it is necessary to
create them by hand. There are three commands that do this.
+@itemize
+
+@item
The easiest command is @code{\new}, and it also the quickest to type.
It is prepended to a music expression, for example
-@cindex @code{\new}
+@funindex \new
@cindex new contexts
@cindex Context, creating
interpreting the @var{music expression} with that.
A practical application of @code{\new} is a score with many
-staves. Each part that should be on its own staff, is preceded with
+staves. Each part that should be on its own staff, is preceded with
@code{\new Staff}.
-@lilypond[quote,verbatim,relative=2,raggedright,fragment]
-<< \new Staff { c4 c }
- \new Staff { d4 d }
+@lilypond[quote,verbatim,relative=2,ragged-right,fragment]
+<<
+ \new Staff { c4 c }
+ \new Staff { d4 d }
>>
@end lilypond
-@cindex @code{\context}
+The @code{\new} command may also give a name to the context,
+
+@example
+\new @var{type} = @var{id} @var{music}
+@end example
+However, this user specified name is only used if there is no other
+context already earlier with the same name.
+
+
+@funindex \context
+@item
Like @code{\new}, the @code{\context} command also directs a music
-expression to a context object, but gives the context an extra name. The
+expression to a context object, but gives the context an explicit name. The
syntax is
@example
@end example
This form will search for an existing context of type @var{type}
-called @var{id}. If that context does not exist yet, it is created.
-This is useful if the context is referred to later on. For example, when
+called @var{id}. If that context does not exist yet, a new
+context with the specified name is created. This is useful if
+the context is referred to later on. For example, when
setting lyrics the melody is in a named context
@example
so the texts can be properly aligned to its notes,
@example
-\new Lyrics \lyricsto "@b{tenor}" @var{lyrics}
+\new Lyrics \lyricsto "@b{tenor}" @var{lyrics}
@end example
@noindent
-Another possibility is funneling two different music expressions into
-one context. In the following example, articulations and notes are
-entered separately,
+Another possible use of named contexts is funneling two different
+music expressions into one context. In the following example,
+articulations and notes are entered separately,
@example
music = @{ c4 c4 @}
arts = @{ s4-. s4-> @}
@end example
-They are combined by sending both to the same @context{Voice} context,
+They are combined by sending both to the same @code{Voice} context,
@example
-<< \new Staff \context Voice = "A" \music
- \context Voice = "A" \arts
+<<
+ \new Staff \context Voice = "A" \music
+ \context Voice = "A" \arts
>>
@end example
-@lilypond[quote,raggedright]
+@lilypond[quote,ragged-right]
music = { c4 c4 }
arts = { s4-. s4-> }
\relative c'' <<
@cindex creating contexts
+@item
The third command for creating contexts is
@example
\context @var{type} @var{music}
any context of type @var{type}, regardless of its given name.
This variant is used with music expressions that can be interpreted at
-several levels. For example, the @code{\applyoutput} command (see
+several levels. For example, the @code{\applyOutput} command (see
@ref{Running a function on all layout objects}). Without an explicit
-@code{\context}, it is usually applied to @context{Voice}
+@code{\context}, it is usually applied to @code{Voice}
@example
-\applyoutput #@var{function} % apply to Voice
+\applyOutput #'@var{context} #@var{function} % apply to Voice
@end example
-To have it interpreted at the @context{Score} or @context{Staff} level use
+To have it interpreted at the @code{Score} or @code{Staff} level use
these forms
@example
-\context Score \applyoutput #@var{function}
-\context Staff \applyoutput #@var{function}
-@end example
-
-
-@node Changing context properties on the fly
-@subsection Changing context properties on the fly
-
-@cindex properties
-@cindex @code{\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,
-
-@example
-\set @var{context}.@var{prop} = #@var{value}
-@end example
-
-For example,
-@lilypond[quote,verbatim,relative=2,fragment]
-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 current bottom-most
-context (typically @context{ChordNames}, @context{Voice}, or
-@context{Lyrics}) is used. In this example,
-
-@lilypond[quote,verbatim,relative=2,fragment]
-c8 c c c
-\set autoBeaming = ##f
-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 @internalsref{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]
-R1*2
-\set skipBars = ##t
-R1*2
-@end lilypond
-
-Contexts are hierarchical, so if a bigger context was specified, for
-example @context{Staff}, then the change would also apply to all
-@context{Voice}s in the current stave. The change is applied
-`on-the-fly', during the music, so that the setting only affects the
-second group of eighth notes.
-
-@cindex @code{\unset}
-
-There is also an @code{\unset} command,
-@example
-\unset @var{context}.@var{prop}
-@end example
-
-@noindent
-which removes the definition of @var{prop}. This command removes
-the definition only if it is set in @var{context}, so
-
-@example
-\set Staff.autoBeaming = ##f
-@end example
-
-@noindent
-introduces a property setting at @code{Staff} level. The setting also
-applies to the current @code{Voice}. However,
-
-@example
-\unset Voice.autoBeaming
-@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
-@example
-\unset Staff.autoBeaming
+\applyOutput #'Score #@var{function}
+\applyOutput #'Staff #@var{function}
@end example
-Like @code{\set}, the @var{context} argument does not have to be
-specified for a bottom context, so the two statements
-
-@example
-\set Voice.autoBeaming = ##t
-\set autoBeaming = ##t
-@end example
-
-@noindent
-are equivalent.
-
-
-@cindex \once
-Settings that should only apply to a single time-step can be entered
-with @code{\once}, for example in
-
-@lilypond[quote,verbatim,relative=2,fragment]
-c4
-\once \set fontSize = #4.7
-c4
-c4
-@end lilypond
-
-the property @code{fontSize} is unset automatically after the second
-note.
-
-A full description of all available context properties is in the
-program reference, see
-@ifhtml
-@internalsref{Tunable context properties}.
-@end ifhtml
-@ifnothtml
-Translation @arrow{} Tunable context properties.
-@end ifnothtml
+@end itemize
@node Modifying context plug-ins
@subsection Modifying context plug-ins
-Notation contexts (like Score and Staff) not only store properties,
-they also contain plug-ins, called ``engravers'' that create notation
-elements. For example, the Voice context contains a
-@code{Note_head_engraver} and the Staff context contains a
+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}.
-For a full a description of each plug-in, see
+For a full a description of each plug-in, see
@ifhtml
-@internalsref{Engravers}.
+@rinternals{Engravers and Performers}.
@end ifhtml
@ifnothtml
-Program reference @arrow Translation @arrow{} Engravers.
+Internals Reference @expansion{} Translation @expansion{} Engravers.
@end ifnothtml
Every context described in
@ifhtml
-@internalsref{Contexts}
+@rinternals{Contexts}
@end ifhtml
-@ifnothtml
-Program reference @arrow Translation @arrow{} Context.
+@ifnothtml
+Internals Reference @expansion{} Translation @expansion{} Context.
@end ifnothtml
lists the engravers used for that context.
It can be useful to shuffle around these plug-ins. This is done by
-starting a new context, with @code{\new} or @code{\context}, and
-modifying it like this,
+starting a new context with @code{\new} or @code{\context}, and
+modifying it,
+
+@funindex \with
@example
\new @var{context} \with @{
\remove @dots{}
@emph{etc.}
@}
-@emph{..music..}
+@{
+ @emph{..music..}
+@}
@end example
@noindent
@code{Clef_engraver} from a @code{Staff} context,
@lilypond[quote,relative=1,verbatim,fragment]
-<< \new Staff {
+<<
+ \new Staff {
f2 g
}
\new Staff \with {
In the second staff there are no time signature or clef symbols. This
is a rather crude method of making objects disappear since it will affect
-the entire staff. The spacing is adversely influenced too. A more
-sophisticated method of blanking objects is shown in @ref{Common tweaks}.
+the entire staff. This method also influences the spacing, which may or
+may not be desirable. More sophisticated methods of blanking objects
+are shown in @rlearning{Visibility and color of objects}.
The next example shows a practical application. Bar lines and time
signatures are normally synchronized across the score. This is done
-by the @code{Timing_engraver}. This plug-in keeps an administration of
-time signature, location within the measure, etc. By moving the
-@code{Timing_engraver} engraver from @code{Score} to @code{Staff}
-context, we can have a score where each staff has its own time
-signature.
+by the @code{Timing_translator} and @code{Default_bar_line_engraver}.
+This plug-in keeps an administration of time signature, location
+within the measure, etc. By moving these engraver from @code{Score} to
+@code{Staff} context, we can have a score where each staff has its own
+time signature.
@cindex polymetric scores
@cindex Time signatures, multiple
-@lilypond[quote,relative=1,raggedright,verbatim,fragment]
+@lilypond[quote,relative=1,ragged-right,verbatim,fragment]
\new Score \with {
- \remove "Timing_engraver"
+ \remove "Timing_translator"
+ \remove "Default_bar_line_engraver"
} <<
\new Staff \with {
- \consists "Timing_engraver"
+ \consists "Timing_translator"
+ \consists "Default_bar_line_engraver"
} {
\time 3/4
c4 c c c c c
}
\new Staff \with {
- \consists "Timing_engraver"
+ \consists "Timing_translator"
+ \consists "Default_bar_line_engraver"
} {
\time 2/4
c4 c c c c c
@end lilypond
-@node Layout tunings within contexts
-@subsection Layout tunings within contexts
-
-Each context is responsible for creating certain types of graphical
-objects. The settings used for printing these objects are also stored by
-context. By changing these settings, the appearance of objects can be
-altered.
-
-The syntax for this is
-
-@example
-\override @var{context}.@var{name} #'@var{property} = #@var{value}
-@end example
-
-Here @var{name} is the name of a graphical object, like @code{Stem} or
-@code{NoteHead}, and @var{property} is an internal variable of the
-formatting system (`grob property' or `layout property'). The latter is a
-symbol, so it must be quoted. The subsection @ref{Constructing a
-tweak} explains what to fill in for @var{name}, @var{property}, and
-@var{value}. Here we only discuss the functionality of this command.
-
-The command
-
-@verbatim
-\override Staff.Stem #'thickness = #4.0
-@end verbatim
-
-@noindent
-makes stems thicker (the default is 1.3, with staff line thickness as a
-unit). Since the command specifies @context{Staff} as context, it only
-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]
-c4
-\override Staff.Stem #'thickness = #4.0
-c4
-c4
-c4
-@end lilypond
-
-The @code{\override} command changes the definition of the @code{Stem}
-within the current @context{Staff}. After the command is interpreted
-all stems are thickened.
-
-Analogous to @code{\set}, the @var{context} argument may be left out,
-causing it to default to @context{Voice}, and adding @code{\once} applies
-the change during one timestep only
-
-@lilypond[quote,fragment,verbatim,relative=2]
-c4
-\once \override Stem #'thickness = #4.0
-c4
-c4
-@end lilypond
-
-The @code{\override} must be done before the object is
-started. Therefore, when altering @emph{Spanner} objects, like slurs 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]
-\override Slur #'thickness = #3.0
-c8[( c
-\override Beam #'thickness = #0.6
-c8 c])
-@end lilypond
-
-@noindent
-the slur is fatter but the beam is not. This is because the command for
-@code{Beam} comes after the Beam is started. Therefore it has no effect.
-
-Analogous to @code{\unset}, the @code{\revert} command for a context
-undoes an @code{\override} command; like with @code{\unset}, it only
-affects settings that were made in the same context. In other words, the
-@code{\revert} in the next example does not do anything.
-
-@example
-\override Voice.Stem #'thickness = #4.0
-\revert Staff.Stem #'thickness
-@end example
-
-
-
-
-@seealso
-
-Internals: @internalsref{OverrideProperty}, @internalsref{RevertProperty},
-@internalsref{PropertySet}, @internalsref{Backend}, and
-@internalsref{All layout objects}.
-
-
-@refbugs
-
-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 Changing context default settings
@subsection Changing context default settings
-The adjustments of the previous subsections (@ref{Changing context
-properties on the fly}, @ref{Modifying context plug-ins}, and
-@ref{Layout tunings within contexts}) can also be entered separately
-from the music, in the @code{\layout} block,
+The adjustments of the previous subsections (
+@ref{The \set command}, @ref{Modifying context plug-ins}, and
+@ref{Overview of modifying properties}) can also be entered
+separately from the music in the @code{\layout} block,
@example
\layout @{
@}
@end example
-Here
-@example
-\Staff
-@end example
-
-@noindent
-takes the existing definition for context @context{Staff} from the
-identifier @code{\Staff}.
+The @code{\Staff} command brings in the existing definition of the
+staff context so that it can be modified.
The statements
@example
@end example
@noindent
-affect all staves in the score.
-
-Other contexts can be modified analogously.
+affect all staves in the score. Other contexts can be modified
+analogously.
The @code{\set} keyword is optional within the @code{\layout} block, so
-@refbugs
+@knownissues
-It is not possible to collect context changes in a variable, and apply
-them to one @code{\context} definition by referring to that variable.
+It is not possible to collect context changes in a variable and apply
+them to a @code{\context} definition by referring to that variable.
-The @code{\RemoveEmptyStaffContext} will override your current
-@code{\Staff} variable. If you wish to change the defaults for a
-staff that uses @code{\RemoveEmptyStaffContext}, you must do so
-after calling @code{\RemoveemptyStaffContext}, ie
+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
@example
\layout @{
@}
@end example
+TODO: add \with in here.
+
+
@node Defining new contexts
@subsection Defining new contexts
-Specific contexts, like @context{Staff} and @code{Voice}, are made of
-simple building blocks, and it is possible to compose engraver
-plug-ins in different combinations, thereby creating new types of
-contexts.
+Specific contexts, like @code{Staff} and @code{Voice}, are made of
+simple building blocks. It is possible to create new types of
+contexts with different combinations of engraver plug-ins.
The next example shows how to build a different type of
-@context{Voice} context from scratch. It will be similar to
-@code{Voice}, but prints centered slash noteheads only. It can be used
-to indicate improvisation in Jazz pieces,
+@code{Voice} context from scratch. It will be similar to
+@code{Voice}, but only prints centered slash note heads. It can be used
+to indicate improvisation in jazz pieces,
-@lilypond[quote,raggedright]
+@lilypond[quote,ragged-right]
\layout { \context {
\name ImproVoice
- \type "Engraver_group_engraver"
+ \type "Engraver_group"
\consists "Note_heads_engraver"
\consists "Text_engraver"
\consists Pitch_squash_engraver
}}
\relative c'' {
- a4 d8 bes8 \new ImproVoice { c4^"ad lib" c
- c4 c^"undress" c_"while playing :)" c }
- a1
+ a4 d8 bes8 \new ImproVoice { c4^"ad lib" c
+ c4 c^"undress" c_"while playing :)" c }
+ a1
}
@end lilypond
-These settings are again done within a @code{\context} block inside a
+These settings are defined within a @code{\context} block inside a
@code{\layout} block,
@example
@}
@end example
-In the following discussion, the example input shown should go on the
-@dots{} in the previous fragment.
+In the following discussion, the example input shown should go in place
+of the @dots{} in the previous fragment.
-First, the context gets a name. Instead of @context{Voice} it
-will be called @context{ImproVoice},
+First it is necessary to define a name for the new context:
@example
\name ImproVoice
@end example
-Since it is similar to the @context{Voice}, we want commands that work
-on (existing) @context{Voice}s to remain working. This is achieved by
-giving the new context an alias @context{Voice},
+Since it is similar to the @code{Voice}, we want commands that work
+on (existing) @code{Voice}s to remain working. This is achieved by
+giving the new context an alias @code{Voice},
@example
\alias Voice
@end example
-The context will print notes, and instructive texts
+The context will print notes and instructive texts, so we need to add
+the engravers which provide this functionality,
@example
\consists Note_heads_engraver
\consists Text_engraver
@end example
-but only on the center line,
+but we only need this on the center line,
@example
\consists Pitch_squash_engraver
squashedPosition = #0
@end example
-The @internalsref{Pitch_squash_engraver} modifies note heads (created
-by @internalsref{Note_heads_engraver}) and sets their vertical
+The @rinternals{Pitch_squash_engraver} modifies note heads (created
+by @rinternals{Note_heads_engraver}) and sets their vertical
position to the value of @code{squashedPosition}, in this case@tie{}@code{0},
the center line.
-The notes look like a slash, without a stem,
+The notes look like a slash, and have no stem,
@example
\override NoteHead #'style = #'slash
\override Stem #'transparent = ##t
@end example
-
All these plug-ins have to cooperate, and this is achieved with a
special plug-in, which must be marked with the keyword @code{\type}.
-This should always be @internalsref{Engraver_group_engraver},
+This should always be @rinternals{Engraver_group},
@example
-\type "Engraver_group_engraver"
+\type "Engraver_group"
@end example
Put together, we get
@example
\context @{
\name ImproVoice
- \type "Engraver_group_engraver"
+ \type "Engraver_group"
\consists "Note_heads_engraver"
\consists "Text_engraver"
\consists Pitch_squash_engraver
@}
@end example
-Contexts form hierarchies. We want to hang the @context{ImproVoice}
-under @context{Staff}, just like normal @code{Voice}s. Therefore, we
+@funindex \accepts
+Contexts form hierarchies. We want to hang the @code{ImproVoice}
+under @code{Staff}, just like normal @code{Voice}s. Therefore, we
modify the @code{Staff} definition with the @code{\accepts}
-command,@footnote{The opposite of @code{\accepts} is @code{\denies},
-which is sometimes needed when reusing existing context definitions.}
-
-
+command,
@example
\context @{
\Staff
- \accepts ImproVoice
+ \accepts ImproVoice
@}
@end example
+@funindex \denies
+The opposite of @code{\accepts} is @code{\denies},
+which is sometimes needed when reusing existing context definitions.
+
Putting both into a @code{\layout} block, like
@example
\relative c'' @{
a4 d8 bes8
\new ImproVoice @{
- c4^"ad lib" c
+ c4^"ad lib" c
c4 c^"undress"
c c_"while playing :)"
@}
a1
@}
@end example
-
-
-
-
-@node The \override command
-@section The \override command
-
-In the previous section, we have already touched on a command that
-changes layout details: the @code{\override} command. In this section,
-we will look in more detail at how to use the command in practice.
-First, we will give a few versatile commands that are sufficient
-for many situations. The next section will discuss the general use of
-@code{\override}.
-
-
-@menu
-* Common tweaks::
-* Constructing a tweak::
-* Navigating the program reference::
-* Layout interfaces::
-* Determining the grob property::
-* Difficult tweaks::
-@end menu
-
-
-
-@node Common tweaks
-@subsection Common tweaks
-@c Should we point at ly/property-init.ly ? -gp
-Some overrides are so common that predefined commands are provided as
-short-cuts, for example, @code{\slurUp} and @code{\stemDown}. These
-commands are described in
-@ifhtml
-the
-@end ifhtml
-@c @ref{Notation manual},
-Notation manual
-@c FIXME
-under the sections for slurs and stems
-respectively.
-
-The exact tuning possibilities for each type of layout object are
-documented in the program reference of the respective
-object. However, many layout objects share properties, which can be
-used to apply generic tweaks. We mention a few of these:
-
-@itemize @bullet
-@item The @code{extra-offset} property, which
-@cindex @code{extra-offset}
-has a pair of numbers as value, moves objects around in the printout.
-The first number controls left-right movement; a positive number will
-move the object to the right. The second number controls up-down
-movement; a positive number will move it higher. The units of these
-offsets are staff-spaces. The @code{extra-offset} property is a
-low-level feature: the formatting engine is completely oblivious to
-these offsets.
-
-In the following example, the second fingering is moved a little to
-the left, and 1.8 staff space downwards:
-
-@cindex setting object properties
-
-@lilypond[quote,fragment,relative=1,verbatim]
-\stemUp
-f-5
-\once \override Fingering
- #'extra-offset = #'(-0.3 . -1.8)
-f-5
-@end lilypond
-@item
-Setting the @code{transparent} property will cause an object to be printed
-in `invisible ink': the object is not printed, but all its other
-behavior is retained. The object still takes up space, it takes part in
-collisions, and slurs, ties, and beams can be attached to it.
-
-@cindex transparent objects
-@cindex removing objects
-@cindex hiding objects
-@cindex invisible objects
-The following example demonstrates how to connect different voices
-using ties. Normally, ties only connect two notes in the same
-voice. By introducing a tie in a different voice,
-
-@lilypond[quote,fragment,relative=2]
-<< {
- b8~ b8\noBeam
-} \\ {
- b[ g8]
-} >>
-@end lilypond
+@node Aligning contexts
+@subsection Aligning contexts
-@noindent
-and blanking the first up-stem in that voice, the tie appears to cross
-voices:
+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,
-@lilypond[quote,fragment,relative=2,verbatim]
-<< {
- \once \override Stem #'transparent = ##t
- b8~ b8\noBeam
-} \\ {
- b[ g8]
-} >>
-@end lilypond
+FIXME: this section doesn't work in pdf. (?)
-@item
-The @code{padding} property for objects with
-@cindex @code{padding}
-@code{side-position-interface} can be set to increase the distance between
-symbols that are printed above or below notes. We provide two
-examples; a more elaborate explanation is in @ref{Constructing a
-tweak}:
-
-@lilypond[quote,fragment,relative=1,verbatim]
-c2\fermata
-\override Script #'padding = #3
-b2\fermata
-@end lilypond
+@cindex ossia
+@findex alignAboveContext
+@findex alignBelowContext
-@lilypond[quote,fragment,relative=1,verbatim]
-% This will not work, see below:
-\override MetronomeMark #'padding = #3
-\tempo 4=120
-c1
-% This works:
-\override Score.MetronomeMark #'padding = #3
-\tempo 4=80
-d1
+@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 }
+ >>
+ }
+}
@end lilypond
-Note in the second example how important it is to figure out what
-context handles a certain object. Since the @code{MetronomeMark} object
-is handled in the Score context, property changes in the @code{Voice}
-context will not be noticed.
-
-@end itemize
-
-More specific overrides are also possible. The next section
-discusses in depth how to figure out these statements for yourself.
-
-
-@node Constructing a tweak
-@subsection Constructing a tweak
-
-The general procedure of changing output, that is, entering
-a command like
-
-@example
-\override Voice.Stem #'thickness = #3.0
-@end example
-
-@noindent
-means that we have to determine these bits of information:
-@itemize
-@item the context: here @context{Voice}.
-@item the layout object: here @code{Stem}.
-@item the layout property: here @code{thickness}
-@item a sensible value: here @code{3.0}
-@end itemize
+@node Explaining the Internals Reference
+@section Explaining the Internals Reference
-@cindex internal documentation
-@cindex finding graphical objects
-@cindex graphical object descriptions
-@cindex tweaking
-@cindex @code{\override}
-@cindex internal documentation
-
-We demonstrate how to glean this information from the notation manual
-and the program reference.
+@menu
+* Navigating the program reference::
+* Layout interfaces::
+* Determining the grob property::
+* Naming conventions::
+@end menu
@node Navigating the program reference
@subsection Navigating the program reference
@end lilypond
If you visit the documentation on fingering instructions (in
-@ref{Fingering instructions}), you will notice that there is written:
+@ref{Fingering instructions}), you will notice:
@quotation
-@seealso
+@strong{See also}
-Program reference: @internalsref{FingerEvent} and @internalsref{Fingering}.
+Internals Reference: @rinternals{Fingering}.
@end quotation
-
+@c outdated info; probably will delete.
+@ignore
This fragment points to two parts of the program reference: a page
on @code{FingerEvent} and one on @code{Fingering}.
forward. For example, it says
@quotation
-Accepted by: @internalsref{Fingering_engraver},
-@end quotation
+Accepted by: @rinternals{Fingering_engraver},
+@end quotation
@noindent
That link brings us to the documentation for the Engraver, the
plug-in, which says
@quotation
-This engraver creates the following layout objects: @internalsref{Fingering}.
+This engraver creates the following layout objects: @rinternals{Fingering}.
@end quotation
In other words, once the @code{FingerEvent}s are interpreted, the
@code{Fingering_engraver} plug-in will process them.
-The @code{Fingering_engraver} is also listed to create
-@internalsref{Fingering} objects,
+@end ignore
+
+@ignore
+@c I can't figure out what this is supposed to mean. -gp
+The @code{Fingering_engraver} is also listed to create
+@rinternals{Fingering} objects,
-Lo and behold, that is also the
+@c old info? it doesn't make any sense to me with our current docs.
+This is also the
second bit of information listed under @b{See also} in the Notation
-manual. By clicking around in the program reference, we can follow the
-flow of information within the program, either forward (like we did
-here), or backwards, following links like this:
+manual.
+@end ignore
+
+@ifnothtml
+The programmer's reference is available as an HTML document. It is
+highly recommended that you read it in HTML form, either online or
+by downloading the HTML documentation. This section will be much more
+difficult to understand if you are using the
+PDF manual.
+@end ifnothtml
+
+Follow the link to @rinternals{Fingering}. At the top of the
+page, you will see
+
+@quotation
+Fingering objects are created by: @rinternals{Fingering_engraver} and
+@rinternals{New_fingering_engraver}.
+@end quotation
+
+By following related links inside the program reference, we can follow the
+flow of information within the program:
-@itemize @bullet
+@itemize
-@item @internalsref{Fingering}:
-@internalsref{Fingering} objects are created by:
-@b{@internalsref{Fingering_engraver}}
+@item @rinternals{Fingering}:
+@rinternals{Fingering} objects are created by:
+@rinternals{Fingering_engraver}
-@item @internalsref{Fingering_engraver}:
-Music types accepted: @b{@internalsref{fingering-event}}
+@item @rinternals{Fingering_engraver}:
+Music types accepted: @rinternals{fingering-event}
-@item @internalsref{fingering-event}:
+@item @rinternals{fingering-event}:
Music event type @code{fingering-event} is in Music expressions named
-@b{@internalsref{FingerEvent}}
+@rinternals{FingerEvent}
@end itemize
This path goes against the flow of information in the program: it
-starts from the output, and ends at the input event.
+starts from the output, and ends at the input event. You could
+also start at an input event, and read with the flow of
+information, eventually ending up at the output object(s).
The program reference can also be browsed like a normal document. It
-contains a chapter on
+contains chapters on
@ifhtml
-@internalsref{Music definitions},
+@rinternals{Music definitions},
@end ifhtml
@ifnothtml
@code{Music definitions}
@end ifnothtml
-on @internalsref{Translation}, and the @internalsref{Backend}. Every
-chapter lists all the definitions used, and all properties that may be
+on @rinternals{Translation}, and the @rinternals{Backend}. Every
+chapter lists all the definitions used and all properties that may be
tuned.
-
+
@node Layout interfaces
@subsection Layout interfaces
@cindex layout interface
@cindex grob
-The HTML page that we found in the previous section, describes the
-layout object called @internalsref{Fingering}. Such an object is a
+The HTML page that we found in the previous section describes the
+layout object called @rinternals{Fingering}. Such an object is a
symbol within the score. It has properties that store numbers (like
thicknesses and directions), but also pointers to related objects. A
layout object is also called a @emph{Grob}, which is short for Graphical
-Object. For more details about Grobs, see @internalsref{grob-interface}.
+Object. For more details about Grobs, see @rinternals{grob-interface}.
The page for @code{Fingering} lists the definitions for the
@code{Fingering} object. For example, the page says
@quotation
@code{padding} (dimension, in staff space):
-
-@code{0.6}
+
+@code{0.5}
@end quotation
@noindent
-which means that the number will be kept at a distance of at least 0.6
+which means that the number will be kept at a distance of at least 0.5
of the note head.
typographical element. For example, the Fingering object
has the following aspects
-@itemize @bullet
+@itemize
@item
Its size is independent of the horizontal spacing, unlike slurs or beams.
@item
Horizontally, the center of the symbol should be aligned to the
-center of the notehead.
+center of the note head.
@item
Vertically, the symbol is placed next to the note and the staff.
@item
-The vertical position is also coordinated with other super- and subscript
-symbols.
+The vertical position is also coordinated with other superscript
+and subscript symbols.
@end itemize
Each of these aspects is captured in so-called @emph{interface}s,
-which are listed on the @internalsref{Fingering} page at the bottom
+which are listed on the @rinternals{Fingering} page at the bottom
@quotation
This object supports the following interfaces:
-@internalsref{item-interface},
-@internalsref{self-alignment-interface},
-@internalsref{side-position-interface}, @internalsref{text-interface},
-@internalsref{text-script-interface}, @internalsref{font-interface},
-@internalsref{finger-interface}, and @internalsref{grob-interface}.
+@rinternals{item-interface},
+@rinternals{self-alignment-interface},
+@rinternals{side-position-interface}, @rinternals{text-interface},
+@rinternals{text-script-interface}, @rinternals{font-interface},
+@rinternals{finger-interface}, and @rinternals{grob-interface}.
@end quotation
Clicking any of the links will take you to the page of the respective
object interface. Each interface has a number of properties. Some of
-them are not user-serviceable (``Internal properties''), but others
-are.
+them are not user-serviceable (@q{Internal properties}), but others
+can be modified.
We have been talking of @emph{the} @code{Fingering} object, but actually it
-does not amount to much. The initialization file
-@file{scm/@/define@/-grobs@/.scm} shows the soul of the `object',
+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},
@example
(Fingering
- . ((print-function . ,Text_interface::print)
- (padding . 0.6)
- (staff-padding . 0.6)
+ . ((padding . 0.5)
+ (avoid-slur . around)
+ (slur-padding . 0.2)
+ (staff-padding . 0.5)
(self-alignment-X . 0)
(self-alignment-Y . 0)
(script-priority . 100)
- (font-size . -5)
- (meta . ((interfaces . (finger-interface font-interface
- text-script-interface text-interface
- side-position-interface
- self-alignment-interface
- item-interface))))))
+ (stencil . ,ly:text-interface::print)
+ (direction . ,ly:script-interface::calc-direction)
+ (font-encoding . fetaNumber)
+ (font-size . -5) ; don't overlap when next to heads.
+ (meta . ((class . Item)
+ (interfaces . (finger-interface
+ font-interface
+ text-script-interface
+ text-interface
+ side-position-interface
+ self-alignment-interface
+ item-interface))))))
@end example
@noindent
As you can see, the @code{Fingering} object is nothing more than a
-bunch of variable settings, and the webpage in the Program Reference
+bunch of variable settings, and the webpage in the Internals Reference
is directly generated from this definition.
+
@node Determining the grob property
@subsection Determining the grob property
-
-Recall that we wanted to change the position of the @b{2} in
+Recall that we wanted to change the position of the @b{2} in
@lilypond[quote,fragment,relative=2,verbatim]
c-2
Since the @b{2} is vertically positioned next to its note, we have to
meddle with the interface associated with this positioning. This is
-done using @code{side-position-interface}. The page for this interface
+done using @code{side-position-interface}. The page for this interface
says
@quotation
@cindex padding
@noindent
-below this description, the variable @code{padding} is described as
+Below this description, the variable @code{padding} is described as
@quotation
@table @code
@item padding
(dimension, in staff space)
-Add this much extra space between objects that are next to each other.
+Add this much extra space between objects that are next to each other.
@end table
@end quotation
-By increasing the value of @code{padding}, we can move away the
-fingering. The following command inserts 3 staff spaces of white
+By increasing the value of @code{padding}, we can move the
+fingering away from the note head. The following command inserts
+3 staff spaces of white
between the note and the fingering:
@example
\once \override Voice.Fingering #'padding = #3
@end lilypond
-In this case, the context for this tweak is @context{Voice}. This
+In this case, the context for this tweak is @code{Voice}. This
fact can also be deduced from the program reference, for the page for
-the @internalsref{Fingering_engraver} plug-in says
+the @rinternals{Fingering_engraver} plug-in says
@quotation
-Fingering_engraver is part of contexts: @dots{} @b{@internalsref{Voice}}
+Fingering_engraver is part of contexts: @dots{} @rinternals{Voice}
@end quotation
-@node Difficult tweaks
-@subsection Difficult tweaks
-There are two classes of difficult adjustments. First, when there are
-several of the same objects at one point, and you want to adjust only
-one. For example, if you want to change only one note head in a chord.
+@node Naming conventions
+@subsection Naming conventions
-In this case, the @code{\applyoutput} function must be used. The
-next example defines a Scheme function @code{set-position-font-size}
-that sets the @code{font-size} property, but only
-on objects that have @internalsref{note-head-interface} and are at the
-right Y-position.
+Another thing that is needed, is an overview of the various naming
+conventions:
-@lilypond[quote,verbatim]
-#(define ((set-position-font-size pos size) grob origin current)
- (let*
- ((interfaces (ly:grob-property grob 'interfaces))
- (position (ly:grob-property grob 'staff-position)))
- (if (and
- ; is this a note head?
- (memq 'note-head-interface interfaces)
+ scheme functions: lowercase-with-hyphens (incl. one-word
+names)
+ scheme functions: ly:plus-scheme-style
+ 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
+CamelCase
+ context properties: lowercaseFollowedByCamelCase
+ engravers:
+Capitalized_followed_by_lowercase_and_with_underscores
- ; is the Y coordinate right?
- (= pos position))
+Which of these are conventions and which are rules?
+Which are rules of the underlying language, and which are
+LP-specific?
- ; then do it.
- (set! (ly:grob-property grob 'font-size) size))))
-\relative {
- c
- \applyoutput #(set-position-font-size -2 4)
- <c e g>
-}
+@node Modifying properties
+@section Modifying properties
+
+@menu
+* Overview of modifying properties::
+* The \set command::
+* The \override command::
+* \set versus \override::
+* Objects connected to the input::
+@end menu
+
+
+@node Overview of modifying properties
+@subsection Overview of modifying properties
+
+Each context is responsible for creating certain types of graphical
+objects. The settings used for printing these objects are also stored by
+context. By changing these settings, the appearance of objects can be
+altered.
+
+The syntax for this is
+
+@example
+\override @var{context}.@var{name} #'@var{property} = #@var{value}
+@end example
+
+Here @var{name} is the name of a graphical object, like
+@code{Stem} or @code{NoteHead}, and @var{property} is an internal
+variable of the formatting system (@q{grob property} or @q{layout
+property}). The latter is a symbol, so it must be quoted. The
+subsection @ref{Modifying properties}, explains what to fill in
+for @var{name}, @var{property}, and @var{value}. Here we only
+discuss the functionality of this command.
+
+The command
+
+@verbatim
+\override Staff.Stem #'thickness = #4.0
+@end verbatim
+
+@noindent
+makes stems thicker (the default is 1.3, with staff line thickness as a
+unit). Since the command specifies @code{Staff} as context, it only
+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]
+c4
+\override Staff.Stem #'thickness = #4.0
+c4
+c4
+c4
+@end lilypond
+
+The @code{\override} command changes the definition of the @code{Stem}
+within the current @code{Staff}. After the command is interpreted
+all stems are thickened.
+
+Analogous to @code{\set}, the @var{context} argument may be left out,
+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]
+c4
+\once \override Stem #'thickness = #4.0
+c4
+c4
+@end lilypond
+
+The @code{\override} must be done before the object is
+started. Therefore, when altering @emph{Spanner} objects such as slurs
+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]
+\override Slur #'thickness = #3.0
+c8[( c
+\override Beam #'thickness = #0.6
+c8 c])
@end lilypond
@noindent
-A similar technique can be used for accidentals. In that case, the
-function should check for @code{accidental-interface}.
-
-Another 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} property 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 @bullet
-@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}.
+the slur is fatter but the beam is not. This is because the command for
+@code{Beam} comes after the Beam is started, so it has no effect.
+
+Analogous to @code{\unset}, the @code{\revert} command for a context
+undoes an @code{\override} command; like with @code{\unset}, it only
+affects settings that were made in the same context. In other words, the
+@code{\revert} in the next example does not do anything.
+
+@example
+\override Voice.Stem #'thickness = #4.0
+\revert Staff.Stem #'thickness
+@end example
+
+Some tweakable options are called @q{subproperties} and reside inside
+properties. To tweak those, use commands of the form
+
+@c leave this as a long long
+@example
+\override @var{context}.@var{name} #'@var{property} #'@var{subproperty} = #@var{value}
+@end example
+
+@noindent
+such as
+
+@example
+\override Stem #'details #'beamed-lengths = #'(4 4 3)
+@end example
+
+
+@seealso
+
+Internals: @rinternals{OverrideProperty}, @rinternals{RevertProperty},
+@rinternals{PropertySet}, @rinternals{Backend}, and
+@rinternals{All layout objects}.
+
+
+@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
+
+@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,
+
+@example
+\set @var{context}.@var{prop} = #@var{value}
+@end example
+
+For example,
+@lilypond[quote,verbatim,relative=2,fragment]
+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 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
+@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]
+R1*2
+\set skipBars = ##t
+R1*2
+@end lilypond
+
+Contexts are hierarchical, so if a bigger 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.
+
+@funindex \unset
+
+There is also an @code{\unset} command,
+@example
+\unset @var{context}.@var{prop}
+@end example
+
+@noindent
+which removes the definition of @var{prop}. This command removes
+the definition only if it is set in @var{context}, so
+
+@example
+\set Staff.autoBeaming = ##f
+@end example
+
+@noindent
+introduces a property setting at @code{Staff} level. The setting also
+applies to the current @code{Voice}. However,
+
+@example
+\unset Voice.autoBeaming
+@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
+@example
+\unset Staff.autoBeaming
+@end example
+
+Like @code{\set}, the @var{context} argument does not have to be
+specified for a bottom context, so the two statements
+
+@example
+\set Voice.autoBeaming = ##t
+\set autoBeaming = ##t
+@end example
+
+@noindent
+are equivalent.
+
+
+@cindex \once
+Settings that should only apply to a single time-step can be entered
+with @code{\once}, for example in
+
+@lilypond[quote,verbatim,relative=2,fragment]
+c4
+\once \set fontSize = #4.7
+c4
+c4
+@end lilypond
+
+the property @code{fontSize} is unset automatically after the second
+note.
+
+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
+
+
+
+@node The \override command
+@subsection The @code{\override} command
+
+Commands which change output generally look like
+
+@example
+\override Voice.Stem #'thickness = #3.0
+@end example
+
+@noindent
+To construct this tweak we must determine these bits of information:
+
+@itemize
+@item the context: here @code{Voice}.
+@item the layout object: here @code{Stem}.
+@item the layout property: here @code{thickness}.
+@item a sensible value: here @code{3.0}.
@end itemize
-This procedure is installed into @internalsref{Tie}, so the last part
-of the broken tie is translated up.
+Some tweakable options are called @q{subproperties} and reside inside
+properties. To tweak those, use commands in the form
+
+@example
+\override Stem #'details #'beamed-lengths = #'(4 4 3)
+@end example
+
+@cindex internal documentation
+@cindex finding graphical objects
+@cindex graphical object descriptions
+@cindex tweaking
+@funindex \override
+@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
+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.
-@lilypond[quote,verbatim,raggedright]
-#(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) '() )))
+@node \set versus \override
+@subsection @code{\set} vs. @code{\override}
- (if (and (>= (length siblings) 2)
- (eq? (car (last-pair siblings)) grob))
- (ly:grob-set-property! grob 'extra-offset '(-2 . 5)))))
+We have seen two methods of changing properties: @code{\set} and
+@code{\override}. There are actually two different kinds of
+properties.
-\relative c'' {
- \override Tie #'after-line-breaking-callback =
- #my-callback
- c1 ~ \break c2 ~ c
-}
+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}.
+
+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}.
+
+@code{\override} is actually a shorthand;
+
+@example
+\override @var{context}.@var{name} #'@var{property} = #@var{value}
+@end example
+
+@noindent
+is more or less equivalent to
+
+@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})
+@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.
+
+@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.
+
+
+@node Objects connected to the input
+@subsection Objects connected to the input
+
+TODO: can't use \tweak in a variable
+
+@funindex \tweak
+
+In some cases, it is possible to take a short-cut for tuning graphical
+objects. For objects that result directly from a piece of the input,
+you can use the @code{\tweak} function, for example
+
+@lilypond[relative=2,fragment,verbatim,ragged-right]
+<
+ c
+ \tweak #'color #red d
+ g
+ \tweak #'duration-log #1 a
+>4-\tweak #'padding #10 -.
@end lilypond
+As you can see, properties are set in the objects directly,
+without mentioning the grob name or context where this should be
+applied.
+
+This technique only works for objects that are directly connected to
+an @rinternals{Event} from the input, for example
+
+@itemize
+@item note heads, caused by chord-pitch (i.e., notes inside a chord)
+@item articulation signs, caused by articulation instructions
+@end itemize
+
+It notably does not work for stems and accidentals (these are caused
+by note heads, not by music events) or clefs (these are not caused by
+music inputs, but rather by the change of a property value).
+
+There are very few objects which are @emph{directly} connected to
+output. A normal note (like @code{c4}) is not directly connected
+to output, so
+
+@example
+\tweak #'color #red c4
+@end example
+
@noindent
-When applying this trick, the new @code{after-line-breaking-callback}
-should also call the old @code{after-line-breaking-callback}, if there
-is one. For example, if using this with @code{Slur},
-@code{Slur::after_line_breaking} should also be called.
+does not change color. See @ref{Displaying music expressions}, for
+details.
+
+
+
+@node Common properties
+@section Common properties
+
+@menu
+* Controlling visibility of objects::
+* Line styles::
+* Rotating objects::
+* Aligning objects::
+@end menu
+
+@node Controlling visibility of objects
+@subsection Controlling visibility of objects
+
+
+@node Line styles
+@subsection Line styles
+
+@c TODO: split the following explanations between expressive marks and
+@c text-related stuff. Perhaps create a new subsection named
+@c "Spanner limits", "Spanner boundaries"? -vv
+
+Some performance indications, e.g., @i{rallentando} and
+@i{accelerando} and @i{trills} are written as text and are
+extended over many measures with lines, sometimes dotted or wavy.
+
+These all use the same routines as the glissando for drawing the
+texts and the lines, and tuning their behavior is therefore also
+done in the same way. It is done with a spanner, and the routine
+responsible for drawing the spanners is
+@code{ly:line-interface::print}. This routine determines the
+exact location of the two @i{span points} and draws a line in
+between, in the style requested.
+
+Here is an example of the different line styles available, and how
+to tune them.
+
+@lilypond[relative=2,ragged-right,verbatim,fragment]
+d2 \glissando d'2
+\once \override Glissando #'style = #'dashed-line
+d,2 \glissando d'2
+\override Glissando #'style = #'dotted-line
+d,2 \glissando d'2
+\override Glissando #'style = #'zigzag
+d,2 \glissando d'2
+\override Glissando #'style = #'trill
+d,2 \glissando d'2
+@end lilypond
+
+The information that determines the end-points is computed
+on-the-fly for every graphic object, but it is possible to
+override these.
+
+@lilypond[relative=2,ragged-right,verbatim,fragment]
+e2 \glissando f
+\once \override Glissando #'bound-details #'right #'Y = #-2
+e2 \glissando f
+@end lilypond
+
+The @code{Glissando} object, like any other using the
+@code{ly:line-interface::print} routine, carries a nested
+association list. In the above statement, the value for @code{Y}
+is set to @code{-2} for the association list corresponding to the
+right end point. Of course, it is also possible to adjust the
+left side with @code{left} instead of @code{right}.
+
+If @code{Y} is not set, the value is computed from the vertical
+position of right attachment point of the spanner.
+
+In case of a line break, the values for the span-points are
+extended with contents of the @code{left-broken} and
+@code{right-broken} sublists, for example
+
+@lilypond[relative=2,ragged-right,verbatim,fragment]
+\override Glissando #'breakable = ##T
+\override Glissando #'bound-details #'right-broken #'Y = #-3
+c1 \glissando \break
+f1
+@end lilypond
+
+The following properties can be used for the
+
+@table @code
+@item Y
+This sets the Y-coordinate of the end point, in staff space. By
+default, it is the center of the bound object, so for a glissando
+it points to the vertical center of the note head.
+
+For horizontal spanners, such as text spanner and trill spanners,
+it is hardcoded to 0.
+
+@item attach-dir
+This determines where the line starts and ends in X-direction,
+relative to the bound object. So, a value of @code{-1} (or
+@code{LEFT}) makes the line start/end at the left side of the note
+head it is attached to.
+
+@item X
+This is the absolute coordinate of the end point. It is usually
+computed on the fly, and there is little use in overriding it.
+
+@item stencil
+Line spanners may have symbols at the beginning or end, which is
+contained in this sub-property. This is for internal use, it is
+recommended to use @code{text}.
+
+@item text
+This is a markup that is evaluated to yield stencil. It is used
+to put @i{cresc.} and @i{tr} on horizontal spanners.
+
+@lilypond[quote,ragged-right,fragment,relative=2,verbatim]
+\override TextSpanner #'bound-details #'left #'text
+ = \markup { \small \bold Slower }
+c2\startTextSpan b c a\stopTextSpan
+@end lilypond
+
+@item stencil-align-dir-y
+@item stencil-offset
+Without setting this, the stencil is simply put there at the
+end-point, as defined by the @code{X} and @code{Y} sub properties.
+Setting either @code{stencil-align-dir-y} or @code{stencil-offset}
+will move the symbol at the edge relative to the end point of the
+line
+
+@lilypond[relative=1,fragment,verbatim]
+\override TextSpanner #'bound-details
+ #'left #'stencil-align-dir-y = #DOWN
+\override TextSpanner #'bound-details
+ #'right #'stencil-align-dir-y = #UP
+
+\override TextSpanner #'bound-details
+ #'left #'text = #"gggg"
+\override TextSpanner #'bound-details
+ #'right #'text = #"hhhh"
+c4^\startTextSpan c c c \stopTextSpan
+@end lilypond
+
+@item arrow
+Setting this sub property to @code{#t} produce an arrowhead at the
+end of the line.
+
+@item padding
+This sub property controls the space between the specified
+end-point of the line and the actual end. Without padding, a
+glissando would start and end in the center of each note head.
+
+@end table
+
+FIXME: should this be in NR 3?
+
+The music function \endSpanners terminates spanners and hairpins
+after exactly one note.
+
+@lilypond[verbatim,quote,ragged-right,relative=2,fragment]
+\endSpanners
+c2 \startTextSpan c2
+c2 \< c2
+@end lilypond
+
+When using \endSpanners it is not necessary to close
+\startTextSpan with \stopTextSpan, nor is it necessary to close
+hairpins with \!.
+
+
+
+@seealso
+
+Internals Reference: @rinternals{TextSpanner},
+@rinternals{Glissando}, @rinternals{VoiceFollower},
+@rinternals{TrillSpanner},
+@rinternals{line-spanner-interface}.
+
+
+@node Rotating objects
+@subsection Rotating objects
+
+@node Aligning objects
+@subsection Aligning objects
+
+
+@node Advanced tweaks
+@section Advanced tweaks
+
+@menu
+* Vertical grouping of grobs::
+* Modifying ends of spanners::
+* Modifying stencils::
+@end menu
+
+
+
+
+@node Vertical grouping of grobs
+@subsection Vertical grouping of grobs
+
+The VerticalAlignment and VerticalAxisGroup grobs work together.
+VerticalAxisGroup groups together different grobs like Staff, Lyrics,
+etc. VerticalAlignment then vertically aligns the different grobs
+grouped together by VerticalAxisGroup. There is usually only one
+VerticalAlignment per score but every Staff, Lyrics, etc. has its own
+VerticalAxisGroup.
+
+
+@node Modifying ends of spanners
+@subsection Modifying ends of spanners
+
+
+@node Modifying stencils
+@subsection Modifying stencils
+
+
+
+@node old The \override command
+@section old The @code{\override} command
+
+In the previous section, we have already touched on a command that
+changes layout details: the @code{\override} command. In this section,
+we will look in more detail at how to use the command in practice. The
+general syntax of this command is:
+
+@example
+\override @var{context}.@var{layout_object} #'@var{layout_property} = #@var{value}
+@end example
+
+This will set the @var{layout_property} of the specified @var{layout_object},
+which is a member of the @var{context}, to the @var{value}.
+
+
+
+
+
+@node Discussion of specific tweaks
+@section Discussion of specific tweaks
+
+@menu
+* old Contexts explained::
+@end menu
+
+
+@node old Contexts explained
+@subsection old Contexts explained
+
+When music is printed, a lot of notational elements must be added to the
+output. For example, compare the input and output of the following example:
+
+@lilypond[quote,verbatim,relative=2,fragment]
+cis4 cis2. g4
+@end lilypond
+
+The input is rather sparse, but in the output, bar lines, accidentals,
+clef, and time signature are added. LilyPond @emph{interprets} the
+input. During this step, the musical information is inspected in time
+order, similar to reading a score from left to right. While reading
+the input, the program remembers where measure boundaries are, and which
+pitches require explicit accidentals. This information can be presented on
+several levels. For example, the effect of an accidental is limited
+to a single staff, while a bar line must be synchronized across the
+entire score.
+
+Within LilyPond, these rules and bits of information are grouped in
+@emph{Contexts}. Some examples of contexts are @code{Voice},
+@code{Staff}, and @code{Score}. They are hierarchical, for
+example: a @code{Staff} can contain many @code{Voice}s, and a
+@code{Score} can contain many @code{Staff} contexts.
+
+@quotation
+@sourceimage{context-example,5cm,,}
+@end quotation
+
+Each context has the responsibility for enforcing some notation rules,
+creating some notation objects and maintaining the associated
+properties. For example, the @code{Voice} context may introduce an
+accidental and then the @code{Staff} context maintains the rule to
+show or suppress the accidental for the remainder of the measure. The
+synchronization of bar lines is handled at @code{Score} context.
+
+However, in some music we may not want the bar lines to be
+synchronized -- consider a polymetric score in 4/4 and 3/4 time. In
+such cases, we must modify the default settings of the @code{Score}
+and @code{Staff} contexts.
+
+For very simple scores, contexts are created implicitly, and you need
+not be aware of them. For larger pieces, such as anything with more
+than one staff, they must be
+created explicitly to make sure that you get as many staves as you
+need, and that they are in the correct order. For typesetting pieces
+with specialized notation, it can be useful to modify existing or
+to define new contexts.
+
+
+A complete description of all available contexts is in the program
+reference, see
+@ifhtml
+@rinternals{Contexts}.
+@end ifhtml
+@ifnothtml
+Translation @expansion{} Context.
+@end ifnothtml
+
+@c [TODO: describe propagation]
+
+
projects / lilypond.git / blobdiff