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13 @node Changing defaults
14 @chapter Changing defaults
16 The purpose of LilyPond's design is to provide the finest quality
17 output by default. Nevertheless, it may happen that you need to
18 change this default layout. The layout is controlled through a large
19 number of @q{knobs and switches} collectively called @q{properties}.
20 A tutorial introduction to accessing and modifying these properties
21 can be found in the Learning Manual, see @rlearning{Tweaking output}.
22 This should be read first. This chapter covers similar ground, but
23 in a style more appropriate to a reference manual.
25 @cindex Internals Reference
27 The definitive description of the controls available for tuning can
28 be found in a separate document: @rinternalsnamed{Top,the Internals
29 Reference}. That manual lists all the variables, functions and
30 options available in LilyPond. It is written as a HTML document,
32 @c leave the @uref as one long line.
33 @uref{http://@/lilypond@/.org/@/doc/@/stable/@/Documentation/@/internals/,on@/-line},
34 and is also included with the LilyPond documentation package.
36 Internally, LilyPond uses Scheme (a LISP dialect) to provide
37 infrastructure. Overriding layout decisions in effect accesses the
38 program internals, which requires Scheme input. Scheme elements are
39 introduced in a @file{.ly} file with the hash
40 mark@tie{}@code{#}.@footnote{@rextend{Scheme tutorial}, contains a
41 short tutorial on entering numbers, lists, strings, and symbols in
46 * Interpretation contexts::
47 * Explaining the Internals Reference::
48 * Modifying properties::
49 * Useful concepts and properties::
51 * Using music functions::
55 @node Interpretation contexts
56 @section Interpretation contexts
58 This section describes what contexts are, and how to modify them.
61 * Contexts explained::
62 * Creating and referencing contexts::
63 * Keeping contexts alive::
64 * Modifying context plug-ins::
65 * Changing context default settings::
66 * Defining new contexts::
67 * Context layout order::
72 @rlearning{Contexts and engravers}.
75 @file{ly/engraver-init.ly},
76 @file{ly/performer-init.ly}.
79 @rlsr{Contexts and engravers}.
82 @rinternals{Contexts},
83 @rinternals{Engravers and Performers}.
86 @node Contexts explained
87 @subsection Contexts explained
90 @c TODO Rethink and rewrite
92 >> > > - list of contexts: my *danger unmaintainable*
93 >> > > alarm just went off. I'm
94 I knew it would... And leaving out some of them is perfectly fine
95 with me. I do think that a list like this, with the main contexts and a
96 brief description of what they do (perhaps also with a note about what
97 default behavior is associated with each of them, but this may be
98 unmanageable), should be there, and then we could simply list the
99 remaining ones without further explanation and with links to the IR.
102 @c TODO Improve layout, order and consistency of wording -td
104 @c TODO Add introduction which explains contexts in generality -td
106 @c TODO Describe propagation of property values -td
108 Contexts are arranged hierarchically:
111 * Output definitions - blueprints for contexts::
112 * Score - the master of all contexts::
113 * Top-level contexts - staff containers::
114 * Intermediate-level contexts - staves::
115 * Bottom-level contexts - voices::
118 @node Output definitions - blueprints for contexts
119 @unnumberedsubsubsec Output definitions - blueprints for contexts
121 This section explains the relevance of output definitions when
122 working with contexts. Examples for actual output definitions are
123 given later (see @ref{Changing all contexts of the same type}).
125 @cindex output definitions
127 While music written in a file may refer to context types and
128 names, contexts are created only when the music is actually being
129 interpreted. LilyPond interprets music under control of an
130 @q{output definition} and may do so for several different output
131 definitions, resulting in different output. The output definition
132 relevant for printing music is specified using @code{\layout}.
135 A much simpler output definition used for producing Midi output is
136 specified using @code{\midi}. Several other output definitions
137 are used by LilyPond internally, like when using the part combiner
138 (@ref{Automatic part combining}) or creating music quotes
139 (@ref{Quoting other voices}).
141 Output definitions define the relation between contexts as well as
142 their respective default settings. While most changes will
143 usually be made inside of a @code{\layout} block, Midi-related
144 settings will only have an effect when made within a @code{\midi}
147 @funindex autoBeaming
148 Some settings affect several outputs: for example, if
149 @code{autoBeaming} is turned off in some context, beams count as
150 melismata for the purpose of matching music to lyrics as described
151 in @ref{Automatic syllable durations}. This matching is done both
152 for printed output as well as for Midi. If changes made to
153 @code{autoBeaming} within a context definition of a @code{\layout}
154 block are not repeated in the corresponding @code{\midi} block,
155 lyrics and music will get out of sync in Midi.
159 @file{ly/engraver-init.ly}.
160 @file{ly/performer-init.ly}.
162 @node Score - the master of all contexts
163 @unnumberedsubsubsec Score - the master of all contexts
165 This is the top level notation context. No other context can
166 contain a Score context. By default the Score context handles
167 the administration of time signatures and makes sure that items
168 such as clefs, time signatures, and key-signatures are aligned
171 A Score context is instantiated implicitly when a
172 @code{\score @{@dots{}@}} block is processed.
174 @node Top-level contexts - staff containers
175 @unnumberedsubsubsec Top-level contexts - staff containers
177 @strong{@emph{StaffGroup}}
179 Groups staves while adding a bracket on the left side, grouping
180 the staves together. The bar lines of the contained staves are
181 connected vertically. @code{StaffGroup} only consists of a collection
182 of staves, with a bracket in front and spanning bar lines.
184 @strong{@emph{ChoirStaff}}
186 Identical to @code{StaffGroup} except that the bar lines of the
187 contained staves are not connected vertically.
189 @strong{@emph{GrandStaff}}
191 A group of staves, with a brace on the left side, grouping the
192 staves together. The bar lines of the contained staves are
193 connected vertically.
195 @strong{@emph{PianoStaff}}
197 Just like @code{GrandStaff}, but with support for instrument names
198 to the left of each system.
200 @node Intermediate-level contexts - staves
201 @unnumberedsubsubsec Intermediate-level contexts - staves
203 @strong{@emph{Staff}}
205 Handles clefs, bar lines, keys, accidentals. It can contain
206 @code{Voice} contexts.
208 @strong{@emph{RhythmicStaff}}
210 Like @code{Staff} but for printing rhythms. Pitches are ignored
211 when engraving; the notes are printed on one line. The MIDI
212 rendition retains pitches unchanged.
214 @strong{@emph{TabStaff}}
216 Context for generating tablature. By default lays the music
217 expression out as a guitar tablature, printed on six lines.
219 @strong{@emph{DrumStaff}}
221 Handles typesetting for percussion. Can contain @code{DrumVoice}.
223 @strong{@emph{VaticanaStaff}}
225 Same as @code{Staff}, except that it is designed for typesetting
226 a piece in gregorian style.
228 @strong{@emph{MensuralStaff}}
230 Same as @code{Staff}, except that it is designed for typesetting
231 a piece in mensural style.
233 @node Bottom-level contexts - voices
234 @unnumberedsubsubsec Bottom-level contexts - voices
236 Voice-level contexts initialise certain properties and start
237 appropriate engravers. A bottom-level context is one without
238 @code{defaultchild}. While it is possible to let it
239 accept/@/contain subcontexts, they can only be created and entered
242 @strong{@emph{Voice}}
244 Corresponds to a voice on a staff. This context handles the
245 conversion of dynamic signs, stems, beams, super- and sub-scripts,
246 slurs, ties, and rests. You have to instantiate this explicitly
247 if you require multiple voices on the same staff.
249 @strong{@emph{VaticanaVoice}}
251 Same as @code{Voice}, except that it is designed for typesetting
252 a piece in gregorian style.
254 @strong{@emph{MensuralVoice}}
256 Same as @code{Voice}, with modifications for typesetting a piece in
259 @strong{@emph{Lyrics}}
261 Corresponds to a voice with lyrics. Handles the printing of a
262 single line of lyrics.
264 @strong{@emph{DrumVoice}}
266 The voice context used in a percussion staff.
268 @strong{@emph{FiguredBass}}
270 The context in which @code{BassFigure} objects are created from
271 input entered in @code{\figuremode} mode.
273 @strong{@emph{TabVoice}}
275 The voice context used within a @code{TabStaff} context. Usually
276 left to be created implicitly.
278 @strong{@emph{CueVoice}}
280 A voice context used to render notes of a reduced size, intended
281 primarily for adding cue notes to a staff, see @ref{Formatting
282 cue notes}. Usually left to be created implicitly.
284 @strong{@emph{ChordNames}}
286 Typesets chord names.
291 Then the following, which I don't know what to do with:
293 * GregorianTranscriptionVoice
294 * GregorianTranscriptionStaff
297 Engraves fretboards from chords. Not easy... Not
299 There is now some documentation on FretBoards in the NR, under
300 instrument-specific notation -- cds.
305 Hard coded entry point for LilyPond. Cannot be tuned.
307 Silently discards all musical information given to this
312 @node Creating and referencing contexts
313 @subsection Creating and referencing contexts
318 @cindex referencing contexts
319 @cindex Contexts, creating and referencing
321 LilyPond will create lower-level contexts automatically if a music
322 expression is encountered before a suitable context exists, but this
323 is usually successful only for simple scores or music fragments like
324 the ones in the documentation. For more complex scores it is
325 advisable to specify all contexts explicitly with either the
326 @code{\new} or @code{\context} command. The syntax of
327 these two commands is very similar:
330 [\new | \context] @var{Context} [ = @var{name}] [@var{music-expression}]
334 where either @code{\new} or @code{\context} may be specified.
335 @var{Context} is the type of context which is to be created,
336 @var{name} is an optional name to be given to the particular context
337 being created and @var{music-expression} is a single music expression
338 that is to be interpreted by the engravers and performers in this
341 The @code{\new} prefix without a name is commonly used to create
342 scores with many staves:
344 @lilypond[quote,verbatim]
346 \new Staff \relative {
347 % leave the Voice context to be created implicitly
350 \new Staff \relative {
357 and to place several voices into one staff:
359 @lilypond[quote,verbatim]
361 \new Voice \relative {
365 \new Voice \relative {
373 @code{\new} should always be used to specify unnamed contexts.
375 The difference between @code{\new} and @code{\context} is in the
380 @code{\new} with or without a name will always create a fresh,
381 distinct, context, even if one with the same name already exists:
383 @lilypond[quote,verbatim]
385 \new Voice = "A" \relative {
389 \new Voice = "A" \relative {
397 @code{\context} with a name specified will create a distinct context
398 only if a context of the same type with the same name in the same
399 context hierarchy does not already exist. Otherwise it will be taken
400 as a reference to that previously created context, and its music
401 expression will be passed to that context for interpretation.
403 One application of named contexts is in separating the score layout
404 from the musical content. Either of these two forms is valid:
406 @lilypond[quote,verbatim]
420 \context Voice = "one" {
425 \context Voice = "two" {
434 @lilypond[quote,verbatim]
439 \context Voice = "one" {
442 \context Voice = "two" {
448 \context Voice = "one" {
453 \context Voice = "two" {
463 Alternatively, variables may be employed to similar effect. See
464 @rlearning{Organizing pieces with variables}.
467 @code{\context} with no name will match the first of any previously
468 created contexts of the same type in the same context heirarchy,
469 even one that has been given a name, and its music expression will be
470 passed to that context for interpretation. This form is rarely
471 useful. However, @code{\context} with no name and no music expression
472 is used to set the context in which a Scheme procedure specified with
473 @code{\applyContext} is executed:
476 \new Staff \relative @{
479 \applyContext #(lambda (ctx)
481 (display (ly:context-current-moment ctx)))
488 A context must be named if it is to be referenced later, for example
489 when lyrics are associated with music:
492 \new Voice = "tenor" @var{music}
494 \new Lyrics \lyricsto "tenor" @var{lyrics}
498 For details of associating lyrics with music see
499 @ref{Automatic syllable durations}.
501 The properties of all contexts of a particular type can be modified
502 in a @code{\layout} block (with a different syntax), see
503 @ref{Changing all contexts of the same type}. This construct also
504 provides a means of keeping layout instructions separate from the
505 musical content. If a single context is to be modified, a @code{\with}
506 block must be used, see @ref{Changing just one specific context}.
510 @rlearning{Organizing pieces with variables}.
513 @ref{Changing just one specific context},
514 @ref{Automatic syllable durations}.
517 @node Keeping contexts alive
518 @subsection Keeping contexts alive
520 @cindex contexts, keeping alive
521 @cindex contexts, lifetime
523 Contexts are usually terminated at the first musical moment in
524 which they have nothing to do. So @code{Voice} contexts die as
525 soon as they contain no events, @code{Staff} contexts die as soon
526 as all the @code{Voice} contexts within them contain no events, etc.
527 This can cause difficulties if earlier contexts which have died
528 have to be referenced, for example, when changing staves with
529 @code{\change} commands, associating lyrics with a voice with
530 @code{\lyricsto} commands, or when adding further musical events to
533 There is an exception to this general rule: inside of an
534 @code{@{@dots{}@}} construct (sequential music), the construct's
535 notion of the ``current context'' will descend whenever an element
536 of the sequence ends in a subcontext of the previous current
537 context. This avoids spurious creation of implicit contexts in a
538 number of situations but means that the first context descended
539 into will be kept alive until the end of the expression.
541 In contrast, the contexts of a @code{<<@dots{}>>} construct's
542 (simultaneous music) expression are not carried forth, so
543 enclosing a context creating command in an extra pair of
544 @code{<<@dots{}>>} will keep the context from persisting through
545 all of the enclosing @code{@{@dots{}@}} sequence.
547 Any context can be kept alive by ensuring it has something to do at
548 every musical moment. @code{Staff} contexts are kept alive by
549 ensuring one of their voices is kept alive. One way of doing this
550 is to add spacer rests to a voice in parallel with the real music.
551 These need to be added to every @code{Voice} context which needs to
552 be kept alive. If several voices are to be used sporadically it is
553 safest to keep them all alive rather than attempting to rely on the
554 exceptions mentioned above.
556 In the following example, both voice A and voice B are kept alive
557 in this way for the duration of the piece:
559 @lilypond[quote,verbatim]
560 musicA = \relative { d''4 d d d }
561 musicB = \relative { g'4 g g g }
564 \new Voice = "A" { s1*5 } % Keep Voice "A" alive for 5 bars
565 \new Voice = "B" { s1*5 } % Keep Voice "B" alive for 5 bars
570 \context Voice = "A" {
574 \context Voice = "B" {
578 \context Voice = "A" { \musicA }
579 \context Voice = "B" { \musicB }
580 \context Voice = "A" { \musicA }
591 @cindex lyrics, aligning with sporadic melody
593 The following example shows how a sporadic melody line with lyrics
594 might be written using this approach. In a real situation the
595 melody and accompaniment would consist of several different
598 @lilypond[quote,verbatim]
599 melody = \relative { a'4 a a a }
600 accompaniment = \relative { d'4 d d d }
601 words = \lyricmode { These words fol -- low the mel -- o -- dy }
604 \new Staff = "music" {
606 \new Voice = "melody" {
608 s1*4 % Keep Voice "melody" alive for 4 bars
611 \new Voice = "accompaniment" {
616 \context Voice = "melody" { \melody }
617 \context Voice = "accompaniment" { \accompaniment }
619 \context Voice = "accompaniment" { \accompaniment }
621 \context Voice = "melody" { \melody }
622 \context Voice = "accompaniment" { \accompaniment }
627 \new Lyrics \with { alignAboveContext = #"music" }
628 \lyricsto "melody" { \words }
633 An alternative way, which may be better in many circumstances, is
634 to keep the melody line alive by simply including spacer notes to
635 line it up correctly with the accompaniment:
637 @lilypond[quote,verbatim]
644 accompaniment = \relative {
650 words = \lyricmode { These words fol -- low the mel -- o -- dy }
654 \new Staff = "music" {
656 \new Voice = "melody" {
660 \new Voice = "accompaniment" {
666 \new Lyrics \with { alignAboveContext = #"music" }
667 \lyricsto "melody" { \words }
673 @node Modifying context plug-ins
674 @subsection Modifying context plug-ins
676 @c TODO Should this be Modifying engravers or Modifying contexts?
678 Notation contexts (like @code{Score} and @code{Staff}) not only store
679 properties, they also contain plug-ins called @q{engravers} that create
680 notation elements. For example, the @code{Voice} context contains a
681 @code{Note_heads_engraver} and the @code{Staff} context contains a
684 For a full a description of each plug-in, see
686 @rinternals{Engravers and Performers}.
689 Internals Reference @expansion{} Translation @expansion{} Engravers.
691 Every context described in
693 @rinternals{Contexts}
696 Internals Reference @expansion{} Translation @expansion{} Context.
698 lists the engravers used for that context.
701 It can be useful to shuffle around these plug-ins. This is done by
702 starting a new context with @code{\new} or @code{\context}, and
708 \new @var{context} \with @{
716 @emph{@dots{}music@dots{}}
721 where the @dots{} should be the name of an engraver. Here is a simple
722 example which removes @code{Time_signature_engraver} and
723 @code{Clef_engraver} from a @code{Staff} context,
725 @lilypond[quote,verbatim]
727 \new Staff \relative {
731 \remove "Time_signature_engraver"
732 \remove "Clef_engraver"
739 In the second staff there are no time signature or clef symbols. This
740 is a rather crude method of making objects disappear since it will affect
741 the entire staff. This method also influences the spacing, which may or
742 may not be desirable. More sophisticated methods of blanking objects
743 are shown in @rlearning{Visibility and color of objects}.
745 The next example shows a practical application. Bar lines and time
746 signatures are normally synchronized across the score. This is done
747 by the @code{Timing_translator} and @code{Default_bar_line_engraver}.
748 This plug-in keeps an administration of time signature, location
749 within the measure, etc. By moving these engraver from @code{Score} to
750 @code{Staff} context, we can have a score where each staff has its own
753 @cindex polymetric scores
754 @cindex time signature, multiple
756 @lilypond[quote,verbatim]
760 \consists "Timing_translator"
761 \consists "Default_bar_line_engraver"
768 \consists "Timing_translator"
769 \consists "Default_bar_line_engraver"
779 \remove "Timing_translator"
780 \remove "Default_bar_line_engraver"
788 The order in which the engravers are specified is the order in
789 which they are called to carry out their processing. Usually the
790 order in which the engravers are specified does not matter, but in
791 a few special cases the order is important, for example where one
792 engraver writes a property and another reads it, or where one
793 engraver creates a grob and another must process it.
795 The following orderings are important:
799 the @code{Bar_engraver} must normally be first,
802 the @code{New_fingering_engraver} must come before the
803 @code{Script_column_engraver},
806 the @code{Timing_translator} must come before the
807 @code{Bar_number_engraver}.
813 @file{ly/engraver-init.ly}.
816 @node Changing context default settings
817 @subsection Changing context default settings
819 @cindex default context properties, changing
820 @cindex context properties, changing defaults
822 Context and grob properties can be changed with @code{\set}
823 and @code{\override} commands, as described in
824 @ref{Modifying properties}. These commands create music events,
825 making the changes take effect at the point in time the music
828 In contrast, this section explains how to change the @emph{default}
829 values of context and grob properties at the time the context is
830 created. There are two ways of doing this. One modifies the default
831 values in all contexts of a particular type, the other modifies the
832 default values in just one particular instance of a context.
835 * Changing all contexts of the same type::
836 * Changing just one specific context::
837 * Order of precedence::
840 @node Changing all contexts of the same type
841 @unnumberedsubsubsec Changing all contexts of the same type
843 @cindex \context in \layout block
847 The default context settings which are to be used for typesetting in
848 @code{Score}, @code{Staff}, @code{Voice} and other contexts may be
849 specified in a @code{\context} block within any @code{\layout}
852 Settings for Midi output as opposed to typesetting will have to be
853 separately specified in @code{\midi} blocks (see @ref{Output
854 definitions - blueprints for contexts}).
856 The @code{\layout} block should be placed within the @code{\score}
857 block to which it is to apply, after the music.
863 [context settings for all Voice contexts]
867 [context settings for all Staff contexts]
872 The following types of settings may be specified:
876 An @code{\override} command, but with the context name omitted
878 @lilypond[quote,verbatim]
881 a'4^"Thicker stems" a a a
887 \override Stem.thickness = #4.0
894 Directly setting a context property
896 @lilypond[quote,verbatim]
899 a'4^"Smaller font" a a a
912 A predefined command such as @code{\dynamicUp} or a music
913 expression like @code{\accidentalStyle dodecaphonic}
915 @lilypond[quote,verbatim]
918 a'4^"Dynamics above" a a a
928 \accidentalStyle dodecaphonic
935 A user-defined variable containing a @code{\with} block; for details
936 of the @code{\with} block see
937 @ref{Changing just one specific context}.
939 @lilypond[quote,verbatim]
940 StaffDefaults = \with {
947 a'4^"Smaller font" a a a
962 Property-setting commands can be placed in a @code{\layout} block
963 without being enclosed in a @code{\context} block. Such settings
964 are equivalent to including the same property-setting commands at
965 the start of every context of the type specified. If no context
966 is specified @emph{every} bottom-level context is affected, see
967 @ref{Bottom-level contexts - voices}. The syntax of a
968 property-setting command in a @code{\layout} block is the same as
969 the same command written in the music stream.
971 @lilypond[quote,verbatim]
975 a'4^"Smaller font" a a a
980 \accidentalStyle dodecaphonic
982 \override Voice.Stem.thickness = #4.0
988 @node Changing just one specific context
989 @unnumberedsubsubsec Changing just one specific context
994 The context properties of just one specific context instance can be
995 changed in a @code{\with} block. All other context instances of the
996 same type retain the default settings built into LilyPond and modified
997 by any @code{\layout} block within scope. The @code{\with} block
998 must be placed immediately after the @code{\new} @var{context-type}
1002 \new Staff \with @{ [context settings for this context instance only] @}
1008 Alternatively, if the music is being entered using the short form of the
1009 input mode-specifying commands, e.g. @code{\chords} rather than
1010 @code{\chordmode}, the @code{\with} command must be placed immediately
1011 after the mode-specifying command:
1014 \chords \with @{ [context settings for this (implicit) context instance only] @}
1021 as it is the implicit context created by these short forms which should
1022 be modified. The same consideration applies to the other input
1023 mode-specifying short forms (@code{\drums}, @code{\figures}), see
1026 Since context modifications specified in @code{\with} blocks are inside
1027 music, they will affect @emph{all} outputs (typesetting @emph{and}
1028 Midi) as opposed to changes within an output definition.
1030 The following types of settings may be specified:
1034 An @code{\override} command, but with the context name omitted
1036 @lilypond[quote,verbatim]
1039 \new Voice \with { \override Stem.thickness = #4.0 }
1042 a'4^"Thick stems" a a a
1051 Directly setting a context property
1053 @lilypond[quote,verbatim]
1058 a'4^"Default font" a a a
1062 \new Staff \with { fontSize = #-4 }
1065 a'4^"Smaller font" a a a
1074 A predefined command such as @code{\dynamicUp}
1076 @lilypond[quote,verbatim]
1082 a'4^"Dynamics below" a a a
1087 \new Staff \with { \accidentalStyle dodecaphonic }
1089 \new Voice \with { \dynamicUp }
1092 a'4^"Dynamics above" a a a
1107 @node Order of precedence
1108 @unnumberedsubsubsec Order of precedence
1110 The value of a property which applies at a particular time is
1111 determined as follows:
1115 if an @code{\override} or @code{\set} command in the input stream is
1116 in effect that value is used,
1119 otherwise the default value taken from a @code{\with} statement
1120 on the context initiation statement is used,
1123 otherwise the default value taken from the most recent appropriate
1124 @code{\context} block in the @code{\layout} or @code{\midi} blocks
1128 otherwise the LilyPond built-in default is used.
1133 @rlearning{Modifying context properties}.
1136 @ref{Contexts explained},
1137 @ref{Bottom-level contexts - voices},
1138 @ref{The set command},
1139 @ref{The override command},
1140 @ref{The layout block,,The @code{@bs{}layout} block}.
1143 @node Defining new contexts
1144 @subsection Defining new contexts
1146 @cindex contexts, defining new
1147 @cindex engravers, including in contexts
1156 Specific contexts, like @code{Staff} and @code{Voice}, are made from
1157 simple building blocks. It is possible to create new types of
1158 contexts with different combinations of engraver plug-ins.
1160 The next example shows how to build a different type of
1161 @code{Voice} context from scratch. It will be similar to
1162 @code{Voice}, but only prints centered slash note heads. It can be used
1163 to indicate improvisation in jazz pieces,
1165 @lilypond[quote,ragged-right]
1166 \layout { \context {
1168 \type "Engraver_group"
1169 \consists "Note_heads_engraver"
1170 \consists "Rhythmic_column_engraver"
1171 \consists "Text_engraver"
1172 \consists "Pitch_squash_engraver"
1173 squashedPosition = #0
1174 \override NoteHead.style = #'slash
1179 \accepts "ImproVoice"
1183 a'4 d8 bes8 \new ImproVoice { c4^"ad lib" c
1184 c4 c^"undress" c_"while playing :)" c }
1190 These settings are defined within a @code{\context} block inside a
1191 @code{\layout} block,
1201 In the following discussion, the example input shown should go in place
1202 of the @dots{} in the previous fragment.
1204 First it is necessary to define a name for the new context:
1210 Since it is similar to the @code{Voice} context, we want commands that
1211 work in (existing) @code{Voice} contexts to continue working. This is
1212 achieved by giving the new context an alias of @code{Voice},
1218 The context will print notes and instructive texts, so we need to add
1219 the engravers which provide this functionality, plus the engraver which
1220 groups notes, stems and rests which occur at the same musical moment
1224 \consists "Note_heads_engraver"
1225 \consists "Text_engraver"
1226 \consists "Rhythmic_column_engraver"
1229 The note heads should all be placed on the center line,
1232 \consists "Pitch_squash_engraver"
1233 squashedPosition = #0
1236 The @code{Pitch_squash_engraver} modifies note heads (created
1237 by the @code{Note_heads_engraver}) and sets their vertical
1238 position to the value of @code{squashedPosition}, in this
1239 case@tie{}@code{0}, the center line.
1241 The notes look like a slash, and have no stem,
1244 \override NoteHead.style = #'slash
1248 All these plug-ins have to communicate under the control of the
1249 context. The mechanisms with which contexts communicate are
1250 established by declaring the context @code{\type}. Within a
1251 @code{\layout} block, most contexts will be of type
1252 @code{Engraver_group}. Some special contexts and contexts in
1253 @code{\midi} blocks use other context types. Copying and
1254 modifying an existing context definition will also fill in the
1255 type. Since this example creates a definition from scratch, it
1256 needs to be specified explicitly.
1259 \type "Engraver_group"
1262 Put together, we get
1267 \type "Engraver_group"
1268 \consists "Note_heads_engraver"
1269 \consists "Text_engraver"
1270 \consists "Rhythmic_column_engraver"
1271 \consists "Pitch_squash_engraver"
1272 squashedPosition = #0
1273 \override NoteHead.style = #'slash
1280 Contexts form hierarchies. We want to place the @code{ImproVoice}
1281 context within the @code{Staff} context, just like normal @code{Voice}
1282 contexts. Therefore, we modify the @code{Staff} definition with the
1283 @code{\accepts} command,
1292 @funindex \inherit-acceptability
1293 Often when reusing an existing context definition, the resulting
1294 context can be used anywhere where the original context would have
1300 \inherit-acceptability @var{to} @var{from}
1305 will arrange to have contexts of type @var{to} accepted by all
1306 contexts also accepting @var{from}. For example, using
1311 \inherit-acceptability "ImproVoice" "Voice"
1316 will add an @code{\accepts} for @code{ImproVoice} to both
1317 @code{Staff} and @code{RhythmicStaff} definitions.
1320 The opposite of @code{\accepts} is @code{\denies},
1321 which is sometimes needed when reusing existing context definitions.
1323 Arranging the required pieces into a @code{\layout} block leaves
1332 \inherit-acceptability "ImproVoice" "Voice"
1336 Then the output at the start of this subsection can be entered as
1344 c c_"while playing :)"
1350 To complete this example, changes affecting the context hierarchy
1351 should be repeated in a @code{\midi} block so that Midi output
1352 depends on the same context relations.
1356 Internals Reference:
1357 @rinternals{Note_heads_engraver},
1358 @rinternals{Text_engraver},
1359 @rinternals{Rhythmic_column_engraver},
1360 @rinternals{Pitch_squash_engraver}.
1363 @node Context layout order
1364 @subsection Context layout order
1366 @cindex contexts, layout order
1370 Contexts are normally positioned in a system from top to bottom
1371 in the order in which they are encountered in the input file. When
1372 contexts are nested, the outer context will include inner nested
1373 contexts as specified in the input file, provided the inner contexts
1374 are included in the outer context's @qq{accepts} list. Nested
1375 contexts which are not included in the outer context's @qq{accepts}
1376 list will be repositioned below the outer context rather than nested
1379 The @qq{accepts} list of a context can be changed with the
1380 @code{\accepts} or @code{\denies} commands. @code{\accepts} adds a
1381 context to the @qq{accepts} list and @code{\denies} removes a context
1384 For example, a square-braced staff group is not usually found within a
1385 curved-braced staff with connecting staff bars, and a @code{GrandStaff}
1386 does not accept a @code{StaffGroup} inside it by default.
1388 @lilypond[verbatim,quote]
1395 \new Staff { \set Staff.instrumentName = bottom f'1 }
1400 However, by using the @code{\accepts} command, @code{StaffGroup} can be
1401 added to the @code{GrandStaff} context:
1403 @lilypond[verbatim,quote]
1410 \new Staff { \set Staff.instrumentName = bottom f'1 }
1415 \accepts "StaffGroup"
1421 @code{\denies} is mainly used when a new context is being based on
1422 another, but the required nesting differs. For example, the
1423 @code{VaticanaStaff} context is based on the @code{Staff} context, but
1424 with the @code{VaticanaVoice} context substituted for the @code{Voice}
1425 context in the @qq{accepts} list.
1427 @cindex contexts, implicit
1428 @cindex implicit contexts
1429 @funindex \defaultchild
1431 Note that a context will be silently created implicitly if a
1432 command is encountered when there is no suitable context available
1435 Within a context definition, the type of subcontext to be
1436 implicitly created is specified using @code{\defaultchild}. A
1437 number of music events require a @samp{Bottom} context: when such
1438 an event is encountered, subcontexts are created recursively until
1439 reaching a context with no @samp{defaultchild} setting.
1441 Implicit context creation can at times give rise to unexpected new
1442 staves or scores. Using @code{\new} to create contexts explicitly
1443 avoids those problems.
1445 @cindex alignAboveContext
1446 @cindex alignBelowContext
1447 @funindex alignAboveContext
1448 @funindex alignBelowContext
1450 Sometimes a context is required to exist for just a brief period, a
1451 good example being the staff context for an ossia. This is usually
1452 achieved by introducing the context definition at the appropriate
1453 place in parallel with corresponding section of the main music.
1454 By default, the temporary context will be placed below all the
1455 existing contexts. To reposition it above the context called
1456 @qq{main}, it should be defined like this:
1459 \new Staff \with @{ alignAboveContext = #"main" @}
1462 A similar situation arises when positioning a temporary lyrics
1463 context within a multi-staved layout such as a @code{ChoirStaff},
1464 for example, when adding a second verse to a repeated section.
1465 By default the temporary lyrics context will be placed beneath the
1466 lower staves. By defining the temporary lyrics context with
1467 @code{alignBelowContext} it can be positioned correctly beneath
1468 the (named) lyrics context containing the first verse.
1470 Examples showing this repositioning of temporary contexts can be
1471 found elsewhere --- see @rlearning{Nesting music expressions},
1472 @ref{Modifying single staves} and @ref{Techniques specific to lyrics}.
1476 @rlearning{Nesting music expressions}.
1479 @ref{Modifying single staves},
1480 @ref{Techniques specific to lyrics}.
1483 @rprogram{An extra staff appears}.
1486 @file{ly/engraver-init.ly}.
1489 @node Explaining the Internals Reference
1490 @section Explaining the Internals Reference
1493 * Navigating the program reference::
1494 * Layout interfaces::
1495 * Determining the grob property::
1496 * Naming conventions::
1499 @node Navigating the program reference
1500 @subsection Navigating the program reference
1502 @c TODO remove this (it's in the LM)
1503 @c Replace with more factual directions
1505 Suppose we want to move the fingering indication in the fragment
1508 @lilypond[quote,fragment,verbatim]
1512 If you visit the documentation on fingering instructions (in
1513 @ref{Fingering instructions}), you will notice:
1518 Internals Reference: @rinternals{Fingering}.
1523 @c outdated info; probably will delete.
1525 This fragment points to two parts of the program reference: a page
1526 on @code{FingeringEvent} and one on @code{Fingering}.
1528 The page on @code{FingeringEvent} describes the properties of the music
1529 expression for the input @w{@code{-2}}. The page contains many links
1530 forward. For example, it says
1533 Accepted by: @rinternals{Fingering_engraver},
1537 That link brings us to the documentation for the Engraver, the
1541 This engraver creates the following layout objects: @rinternals{Fingering}.
1544 In other words, once the @code{FingeringEvent}s are interpreted, the
1545 @code{Fingering_engraver} plug-in will process them.
1549 @c I can't figure out what this is supposed to mean. -gp
1551 The @code{Fingering_engraver} is also listed to create
1552 @rinternals{Fingering} objects,
1554 @c old info? it doesn't make any sense to me with our current docs.
1556 second bit of information listed under @b{See also} in the Notation
1561 The programmer's reference is available as an HTML document. It is
1562 highly recommended that you read it in HTML form, either online or
1563 by downloading the HTML documentation. This section will be much more
1564 difficult to understand if you are using the
1568 Follow the link to @rinternals{Fingering}. At the top of the
1572 Fingering objects are created by: @rinternals{Fingering_engraver} and
1573 @rinternals{New_fingering_engraver}.
1576 By following related links inside the program reference, we can follow the
1577 flow of information within the program:
1581 @item @rinternals{Fingering}:
1582 @rinternals{Fingering} objects are created by:
1583 @rinternals{Fingering_engraver}
1585 @item @rinternals{Fingering_engraver}:
1586 Music types accepted: @rinternals{fingering-event}
1588 @item @rinternals{fingering-event}:
1589 Music event type @code{fingering-event} is in Music expressions named
1590 @rinternals{FingeringEvent}
1593 This path goes against the flow of information in the program: it
1594 starts from the output, and ends at the input event. You could
1595 also start at an input event, and read with the flow of
1596 information, eventually ending up at the output object(s).
1598 The program reference can also be browsed like a normal document. It
1599 contains chapters on
1601 @rinternals{Music definitions},
1604 @code{Music definitions}
1606 on @rinternals{Translation}, and the @rinternals{Backend}. Every
1607 chapter lists all the definitions used and all properties that may be
1611 @node Layout interfaces
1612 @subsection Layout interfaces
1614 @cindex interface, layout
1615 @cindex layout interface
1618 The HTML page that we found in the previous section describes the
1619 layout object called @rinternals{Fingering}. Such an object is a
1620 symbol within the score. It has properties that store numbers (like
1621 thicknesses and directions), but also pointers to related objects. A
1622 layout object is also called a @emph{Grob}, which is short for Graphical
1623 Object. For more details about Grobs, see @rinternals{grob-interface}.
1625 The page for @code{Fingering} lists the definitions for the
1626 @code{Fingering} object. For example, the page says
1629 @code{padding} (dimension, in staff space):
1635 which means that the number will be kept at a distance of at least 0.5
1639 Each layout object may have several functions as a notational or
1640 typographical element. For example, the Fingering object
1641 has the following aspects
1645 Its size is independent of the horizontal spacing, unlike slurs or beams.
1648 It is a piece of text. Granted, it is usually a very short text.
1651 That piece of text is typeset with a font, unlike slurs or beams.
1654 Horizontally, the center of the symbol should be aligned to the
1655 center of the note head.
1658 Vertically, the symbol is placed next to the note and the staff.
1661 The vertical position is also coordinated with other superscript
1662 and subscript symbols.
1665 Each of these aspects is captured in so-called @emph{interface}s,
1666 which are listed on the @rinternals{Fingering} page at the bottom
1669 This object supports the following interfaces:
1670 @rinternals{item-interface},
1671 @rinternals{self-alignment-interface},
1672 @rinternals{side-position-interface}, @rinternals{text-interface},
1673 @rinternals{text-script-interface}, @rinternals{font-interface},
1674 @rinternals{finger-interface}, and @rinternals{grob-interface}.
1677 Clicking any of the links will take you to the page of the respective
1678 object interface. Each interface has a number of properties. Some of
1679 them are not user-serviceable (@q{Internal properties}), but others
1682 We have been talking of @emph{the} @code{Fingering} object, but actually it
1683 does not amount to much. The initialization file (see
1684 @rlearning{Other sources of information})
1685 @file{scm/define-grobs.scm} shows the soul of the @q{object},
1690 (avoid-slur . around)
1691 (slur-padding . 0.2)
1692 (staff-padding . 0.5)
1693 (self-alignment-X . 0)
1694 (self-alignment-Y . 0)
1695 (script-priority . 100)
1696 (stencil . ,ly:text-interface::print)
1697 (direction . ,ly:script-interface::calc-direction)
1698 (font-encoding . fetaText)
1699 (font-size . -5) ; don't overlap when next to heads.
1700 (meta . ((class . Item)
1701 (interfaces . (finger-interface
1703 text-script-interface
1705 side-position-interface
1706 self-alignment-interface
1707 item-interface))))))
1711 As you can see, the @code{Fingering} object is nothing more than a
1712 bunch of variable settings, and the webpage in the Internals Reference
1713 is directly generated from this definition.
1716 @node Determining the grob property
1717 @subsection Determining the grob property
1719 @c TODO remove this (it's in the LM)
1720 @c Replace with more factual directions
1722 Recall that we wanted to change the position of the @b{2} in
1724 @lilypond[quote,fragment,verbatim]
1728 Since the @b{2} is vertically positioned next to its note, we have to
1729 meddle with the interface associated with this positioning. This is
1730 done using @code{side-position-interface}. The page for this interface
1734 @code{side-position-interface}
1736 Position a victim object (this one) next to other objects (the
1737 support). The property @code{direction} signifies where to put the
1738 victim object relative to the support (left or right, up or down?)
1743 Below this description, the variable @code{padding} is described as
1748 (dimension, in staff space)
1750 Add this much extra space between objects that are next to each other.
1754 By increasing the value of @code{padding}, we can move the fingering
1755 away from the note head. The following command will insert @qq{three
1756 staff spaces} worth of distance between the note and a fingering mark:
1759 \once \override Voice.Fingering.padding = #3
1762 Inserting the padding before the fingering object is created results in
1765 @lilypond[quote,fragment,verbatim]
1766 \once \override Voice.Fingering.padding = #3
1770 In this case, the context for this tweak is @code{Voice}. See
1771 @rinternals{Fingering_engraver} plug-in, which says:
1774 Fingering_engraver is part of contexts: @dots{} @rinternals{Voice}
1778 @node Naming conventions
1779 @subsection Naming conventions
1781 Another thing that is needed, is an overview of the various naming
1785 @item scheme functions: lowercase-with-hyphens (also includes one-word
1788 @item LilyPond-specific scheme functions: ly:plus-scheme-style
1790 @item music events, music classes and music properties:
1793 @item Grob interfaces: scheme-style
1795 @item backend properties: scheme-style (but X and Y!)
1797 @item contexts (and MusicExpressions and grobs): Capitalized or
1800 @item context properties: lowercaseFollowedByCamelCase
1802 @item engravers: Capitalized_followed_by_lowercase_and_with_underscores
1805 Questions to be answered:
1808 @item Which of these are conventions and which are rules?
1810 @item Which are rules of the underlying language, and which are
1814 @node Modifying properties
1815 @section Modifying properties
1817 @c TODO change the menu and subsection node names to use
1818 @c backslash once the new macro to handle the refs
1819 @c is available. Need to find and change all refs at
1820 @c the same time. -td
1823 * Overview of modifying properties::
1825 * The override command::
1826 * The tweak command::
1827 * set versus override::
1828 * Modifying alists::
1832 @node Overview of modifying properties
1833 @subsection Overview of modifying properties
1835 Each context is responsible for creating certain types of graphical
1836 objects. The settings used for printing these objects are also stored by
1837 context. By changing these settings, the appearance of objects can be
1840 There are two different kinds of properties stored in contexts:
1841 context properties and grob properties. Context properties are
1842 properties that apply to the context as a whole and control
1843 how the context itself is displayed. In contrast, grob properties
1844 apply to specific grob types that will be displayed in the context.
1846 The @code{\set} and @code{\unset} commands are used to change values
1847 for context properties. The @code{\override} and @code{\revert}
1848 commands are used to change values for grob properties.
1851 The syntax for this is
1854 \override @var{context}.@var{name} #'@var{property} = #@var{value}
1857 Here @var{name} is the name of a graphical object, like
1858 @code{Stem} or @code{NoteHead}, and @var{property} is an internal
1859 variable of the formatting system (@q{grob property} or @q{layout
1860 property}). The latter is a symbol, so it must be quoted. The
1861 subsection @ref{Modifying properties}, explains what to fill in
1862 for @var{name}, @var{property}, and @var{value}. Here we only
1863 discuss the functionality of this command.
1868 \override Staff.Stem.thickness = #4.0
1872 makes stems thicker (the default is 1.3, with staff line thickness as a
1873 unit). Since the command specifies @code{Staff} as context, it only
1874 applies to the current staff. Other staves will keep their normal
1875 appearance. Here we see the command in action:
1877 @lilypond[quote,fragment,verbatim]
1879 \override Staff.Stem.thickness = #4.0
1885 The @code{\override} command changes the definition of the @code{Stem}
1886 within the current @code{Staff}. After the command is interpreted
1887 all stems are thickened.
1889 Analogous to @code{\set}, the @var{context} argument may be left out,
1890 causing the default context @code{Voice} to be used. Adding
1891 @code{\once} applies the change during one timestep only.
1893 @lilypond[quote,fragment,verbatim]
1895 \once \override Stem.thickness = #4.0
1900 The @code{\override} must be done before the object is
1901 started. Therefore, when altering @emph{Spanner} objects such as slurs
1902 or beams, the @code{\override} command must be executed at the moment
1903 when the object is created. In this example,
1905 @lilypond[quote,fragment,verbatim]
1906 \override Slur.thickness = #3.0
1908 \override Beam.beam-thickness = #0.6
1913 the slur is fatter but the beam is not. This is because the command for
1914 @code{Beam} comes after the Beam is started, so it has no effect.
1916 Analogous to @code{\unset}, the @code{\revert} command for a context
1917 undoes an @code{\override} command; like with @code{\unset}, it only
1918 affects settings that were made in the same context. In other words, the
1919 @code{\revert} in the next example does not do anything.
1922 \override Voice.Stem.thickness = #4.0
1923 \revert Staff.Stem.thickness
1926 Some tweakable options are called @q{subproperties} and reside inside
1927 properties. To tweak those, use commands of the form
1929 @c leave this as a long long
1931 \override @var{context}.@var{name} #'@var{property} #'@var{subproperty} = #@var{value}
1938 \override Stem.details.beamed-lengths = #'(4 4 3)
1944 Internals Reference:
1945 @rinternals{Backend},
1946 @rinternals{All layout objects},
1947 @rinternals{OverrideProperty},
1948 @rinternals{RevertProperty},
1949 @rinternals{PropertySet}.
1952 The back-end is not very strict in type-checking object properties.
1953 Cyclic references in Scheme values for properties can cause hangs
1954 or crashes, or both.
1957 @node The set command
1958 @subsection The @code{@bs{}set} command
1962 @cindex changing properties
1964 Each context has a set of @emph{properties}, variables contained
1965 in that context. Context properties are changed with the @code{\set}
1966 command, which has the following syntax:
1969 \set @var{context}.@var{property} = #@var{value}
1972 @var{value} is a Scheme object, which is why it must be preceded by
1973 the @code{#}@tie{}character.
1975 Contexts properties are usually named in
1976 @code{studlyCaps}. They mostly control the translation from
1977 music to notation, e.g., @code{localAlterations} (for determining
1978 whether to print accidentals), or @code{measurePosition} (for
1979 determining when to print a bar line). Context properties can
1980 change value over time while interpreting a piece of music;
1981 @code{measurePosition} is an obvious example of
1982 this. Context properties are modified with @code{\set}.
1984 For example, multimeasure rests will be combined into a single bar
1985 if the context property @code{skipBars} is set to @code{#t}:
1987 @lilypond[quote,fragment,verbatim]
1989 \set Score.skipBars = ##t
1993 If the @var{context} argument is left out, then the property will be
1994 set in the current bottom context (typically @code{ChordNames},
1995 @code{Voice}, @code{TabVoice}, or @code{Lyrics}).
1997 @lilypond[quote,fragment,verbatim]
1998 \set Score.autoBeaming = ##f
2001 \set autoBeaming = ##t
2009 The change is applied @q{on-the-fly}, during the music, so that the
2010 setting only affects the second group of eighth notes.
2012 Note that the bottom-most context does not always contain the property
2013 that you wish to change -- for example, attempting to set the
2014 @code{skipBars} property of the default bottom context, in this case
2015 @code{Voice}, will have no effect, because skipBars is a property of
2016 the @code{Score} context.
2018 @lilypond[quote,fragment,verbatim]
2024 Contexts are hierarchical, so if an enclosing context was specified, for
2025 example @code{Staff}, then the change would also apply to all
2026 @code{Voice}s in the current staff.
2030 The @code{\unset} command:
2033 \unset @var{context}.@var{property}
2037 is used to remove the definition of @var{property} from
2038 @var{context}. This command removes
2039 the definition only if it is set in @var{context}.
2040 Properties that have been set in enclosing contexts will
2041 not be altered by an unset in an enclosed context:
2043 @lilypond[quote,fragment,verbatim]
2044 \set Score.autoBeaming = ##t
2048 \unset Score.autoBeaming
2056 Like @code{\set}, the @var{context} argument does not have to be
2057 specified for a bottom context, so the two statements
2060 \set Voice.autoBeaming = ##t
2061 \set autoBeaming = ##t
2065 are equivalent if the current bottom context is @code{Voice}.
2069 Preceding a @code{\set} or @code{\unset} command by @code{\once}
2070 makes the setting apply to only a single time-step:
2072 @lilypond[quote,fragment,verbatim]
2074 \once \set fontSize = #4.7
2079 A full description of all available context properties is in the
2080 internals reference, see
2082 @rinternals{Tunable context properties}.
2085 Translation @expansion{} Tunable context properties.
2089 Internals Reference:
2090 @rinternals{Tunable context properties}.
2093 @node The override command
2094 @subsection The @code{\override} command
2096 @cindex grob properties
2097 @cindex properties, grob
2100 There is a special type of context property: the grob
2101 description. Grob descriptions are named in @code{StudlyCaps}
2102 (starting with capital letters). They contain the
2103 @q{default settings} for a particular kind of grob as an
2104 association list. See @file{scm/define-grobs.scm}
2105 to see the settings for each grob description. Grob descriptions
2106 are modified with @code{\override}.
2108 The syntax for the @code{\override} command is
2111 \override [@var{context}.]@var{GrobName}.@var{property} = #@var{value}
2114 For example, we can increase the thickness of a note stem by
2115 overriding the @code{thickness} property of the @code{Stem}
2118 @lilypond[quote,fragment,verbatim]
2120 \override Voice.Stem.thickness = #3.0
2124 If no context is specified in an @code{\override}, the bottom
2127 @lilypond[quote,fragment,verbatim]
2128 \override Staff.Stem.thickness = #3.0
2132 \override Stem.thickness = #0.5
2141 Some tweakable options are called @q{subproperties} and reside inside
2142 properties. To tweak those, use commands in the form
2145 \override Stem.details.beamed-lengths = #'(4 4 3)
2148 or to modify the ends of spanners, use a form like these
2151 \override TextSpanner.bound-details.left.text = #"left text"
2152 \override TextSpanner.bound-details.right.text = #"right text"
2156 @cindex reverting overrides
2157 @cindex overrides, reverting
2159 The effects of @code{\override} can be undone by @code{\revert}.
2161 The syntax for the @code{\revert} command is
2164 \revert [@var{context}.]@var{GrobName}.@var{property}
2169 @lilypond[quote,verbatim]
2172 \override Voice.Stem.thickness = #3.0
2174 \revert Voice.Stem.thickness
2179 The effects of @code{\override} and @code{\revert} apply to all
2180 grobs in the affected context from the current time forward:
2182 @lilypond[quote,verbatim]
2186 \override Staff.Stem.thickness = #3.0
2191 \revert Staff.Stem.thickness
2198 @cindex overriding for only one moment
2200 @code{\once} can be used with @code{\override} or @code{\revert}
2201 to affect only the current time step:
2203 @lilypond[quote,verbatim]
2206 \override Stem.thickness = #3.0
2211 \once \override Stem.thickness = #3.0
2219 Commands which change output generally look like
2222 \override Voice.Stem.thickness = #3.0
2226 To construct this tweak we must determine these bits of information:
2229 @item the context: here @code{Voice}.
2230 @item the layout object: here @code{Stem}.
2231 @item the layout property: here @code{thickness}.
2232 @item a sensible value: here @code{3.0}.
2235 @cindex internal documentation
2236 @cindex finding graphical objects
2237 @cindex graphical object descriptions
2240 @cindex internal documentation
2242 For many properties, regardless of the data type of the property, setting the
2243 property to false (@code{#f}) will result in turning it off, causing
2244 LilyPond to ignore that property entirely. This is particularly useful for
2245 turning off grob properties which may otherwise be causing problems.
2247 We demonstrate how to glean this information from the notation manual
2248 and the program reference.
2252 Internals Reference:
2253 @rinternals{Backend}
2256 @node The tweak command
2257 @subsection The @code{\tweak} command
2262 Changing grob properties
2263 with @code{\override} causes the changes to apply to all of the
2264 given grobs in the context at the moment the change applies.
2265 Sometimes, however, it is desirable to have changes apply to just
2266 one grob, rather than to all grobs in the affected context. This is
2267 accomplished with the @code{\tweak} command, which has the following
2271 \tweak [@var{layout-object}.]@var{grob-property} @var{value}
2274 Specifying @var{layout-object} is optional.
2275 The @code{\tweak} command applies to the music object that immediately
2276 follows @var{value} in the music stream.
2279 In some cases, it is possible to take a short-cut for tuning
2280 graphical objects. For objects that are created directly from
2281 an item in the input file, you can use the @code{\tweak} command.
2284 @lilypond[verbatim,quote]
2290 \tweak duration-log #1
2300 The main use of the @code{\tweak} command is to modify just
2301 one of a number of notation elements which start at the same musical
2302 moment, like the notes of a chord, or tuplet brackets which start
2305 The @code{\tweak} command sets a property in the following object
2306 directly, without requiring the grob name or context to be
2307 specified. For this to work, it is necessary for the @code{\tweak}
2308 command to remain immediately adjacent to the object to which it is
2309 to apply after the input file has been converted to a music stream.
2310 This is often not the case, as many additional elements are inserted
2311 into the music stream implicitly. For example, when a note which is
2312 not part of a chord is processed, LilyPond implicitly inserts a
2313 @code{ChordEvent} event before the note, so separating the tweak
2314 from the note. However, if chord symbols are placed round the
2315 tweak and the note, the @code{\tweak} command comes after the
2316 @code{ChordEvent} in the music stream, so remaining adjacent to the
2317 note, and able to modify it.
2321 @lilypond[verbatim,fragment,quote]
2322 <\tweak color #red c''>4
2328 @lilypond[verbatim,fragment,quote]
2329 \tweak color #red c''4
2334 For an introduction to the syntax and uses of the tweak command
2335 see @rlearning{Tweaking methods}.
2337 When several similar items are placed at the same musical moment,
2338 the @code{\override} command cannot be used to modify just one of
2339 them -- this is where the @code{\tweak} command must be used.
2340 Items which may appear more than once at the same musical moment
2341 include the following:
2343 @c TODO expand to include any further uses of \tweak
2345 @item note heads of notes inside a chord
2346 @item articulation signs on a single note
2347 @item ties between notes in a chord
2348 @item tuplet brackets starting at the same time
2351 @c TODO add examples of these
2353 @cindex chord, modifying one note in
2355 In this example, the color of one note head and the type of another
2356 note head are modified within a single chord:
2358 @lilypond[verbatim,fragment,quote]
2363 \tweak duration-log #1
2368 @code{\tweak} can be used to modify slurs:
2370 @lilypond[verbatim,quote]
2371 \relative { c'-\tweak thickness #5 ( d e f) }
2375 For the @code{\tweak} command to work, it must
2376 remain immediately adjacent to the object to which it is
2377 to apply after the input file has been converted to a music stream.
2378 Tweaking a whole chord does not do anything since its music event
2379 only acts as a container, and all layout objects are created from events
2380 inside of the @code{EventChord}:
2382 @lilypond[verbatim,fragment,quote]
2383 \tweak color #red c''4
2384 \tweak color #red <c'' e''>4
2385 <\tweak color #red c'' e''>4
2388 The simple @code{\tweak} command cannot be used to modify any object
2389 that is not directly created from the input. In particular
2390 it will not affect stems, automatic
2391 beams or accidentals, since these are generated later by
2392 @code{NoteHead} layout objects rather than by music elements in the
2395 Such indirectly created layout objects can be tweaked using the form
2396 of the @code{\tweak} command in which the grob name is specified
2399 @lilypond[fragment,verbatim,quote]
2400 \tweak Stem.color #red
2401 \tweak Beam.color #green c''8 e''
2402 <c'' e'' \tweak Accidental.font-size #-3 ges''>4
2405 @code{\tweak} cannot be used to modify clefs or time
2406 signatures, since these become separated from any preceding
2407 @code{\tweak} command in the input stream by the automatic
2408 insertion of extra elements required to specify the context.
2410 Several @code{\tweak} commands may be placed before a
2411 notational element -- all affect it:
2413 @lilypond[verbatim,fragment,quote]
2415 -\tweak style #'dashed-line
2416 -\tweak dash-fraction #0.2
2417 -\tweak thickness #3
2423 The music stream which is generated from a section of an input file,
2424 including any automatically inserted elements, may be examined,
2425 see @rextend{Displaying music expressions}. This may be helpful in
2426 determining what may be modified by a @code{\tweak} command, or
2427 in determining how to adjust the input to make a @code{\tweak}
2432 @rlearning{Tweaking methods}.
2435 @rextend{Displaying music expressions}.
2439 @cindex tweaking control points
2440 @cindex control points, tweaking
2442 The @code{\tweak} command cannot be used to modify the control
2443 points of just one of several ties in a chord, other than the first
2444 one encountered in the input file.
2446 @node set versus override
2447 @subsection @code{\set} vs. @code{\override}
2449 @c TODO Should't a bunch of that be explained earlier?
2454 The @code{\set} and @code{\override} commands manipulate properties
2455 associated with contexts. In both cases, the properties follow a
2456 @emph{hierarchy of contexts}; properties that are not set themselves in
2457 a context will still show the values of their respective parent's
2460 The lifetime and value of a context property is dynamic and only
2461 available when music is being interpreted (i.e., @q{iterated}). At the
2462 time of the context's creation, properties are initialized from its
2463 corresponding definitions (along with any other modifications) of that
2464 context. Any subsequent changes are achieved with any
2465 @q{property-setting} commands that are within the music itself.
2467 Graphical Object (or @qq{grob}) definitions are a @emph{special}
2468 category of context properties as their structure and use is different
2469 from that of normal context properties. Unlike normal context
2470 properties, grob definitions are subdivided into @emph{grob properties}.
2472 Also, in contrast to normal context properties, grob definitions have
2473 their own internal @q{bookkeeping} used to keep track of their own
2474 individual grob properties and any sub-properties. This means that it
2475 is possible to define those parts within different contexts and yet
2476 still have the overall grob definition at the time of grob creation from
2477 all the pieces provided amongst the current context and its parent(s).
2479 A grob is usually created by an engraver at the time of interpreting a
2480 music expression and receives its initial properties from the current
2481 grob definition of the engraver's context. The engraver (or other
2482 @q{backend} parts of LilyPond) can then change (or add to) the grob's
2483 initial properties. However, this does not affect the context's own
2486 What LilyPond calls @emph{grob properties} in the context of
2487 @q{user-level} tweaks are really the properties of a @emph{context's}
2488 own grob definition.
2490 Grob definitions are accessed with a different set of commands and are
2491 manipulated using @code{\override} and @code{\revert} and have a name
2492 starting with a capital letter (e.g., @samp{NoteHead}); whereas normal
2493 context properties are manipulated using @code{\set} and @code{\unset}
2494 and are named starting with a lowercase letter.
2496 @cindex tweak, relation to @code{\override}
2498 @funindex \overrideProperty
2500 The commands @code{\tweak} and @code{\overrideProperty} change grob
2501 properties by bypassing all context properties completely and, instead,
2502 catch grobs as they are being created, setting properties on them for
2503 a music event (@code{\tweak}) or, in the case of
2504 @code{\overrideProperty} for a specific override.
2507 @node Modifying alists
2508 @subsection Modifying alists
2510 Some user-configurable properties are internally represented as
2511 @emph{alists} (association lists), which store pairs of
2512 @emph{keys} and @emph{values}. The structure of an alist is:
2515 '((@var{key1} . @var{value1})
2516 (@var{key2} . @var{value2})
2517 (@var{key3} . @var{value3})
2521 If an alist is a grob property or @code{\paper} variable, its keys
2522 can be modified individually without affecting other keys.
2524 For example, to reduce the space between adjacent staves in a
2525 staff-group, use the @code{staff-staff-spacing} property of the
2526 @code{StaffGrouper} grob. The property is an alist with four
2527 keys: @code{basic-distance}, @code{minimum-distance},
2528 @code{padding}, and @code{stretchability}. The standard settings
2529 for this property are listed in the @qq{Backend} section of the
2530 Internals Reference (see @rinternals{StaffGrouper}):
2533 '((basic-distance . 9)
2534 (minimum-distance . 7)
2536 (stretchability . 5))
2539 One way to bring the staves closer together is by reducing the
2540 value of the @code{basic-distance} key (@code{9}) to match the
2541 value of @code{minimum-distance} (@code{7}). To modify a single
2542 key individually, use a @emph{nested declaration}:
2544 @lilypond[quote,verbatim]
2545 % default space between staves
2547 \new Staff { \clef treble c''1 }
2548 \new Staff { \clef bass c1 }
2551 % reduced space between staves
2552 \new PianoStaff \with {
2553 % this is the nested declaration
2554 \override StaffGrouper.staff-staff-spacing.basic-distance = #7
2556 \new Staff { \clef treble c''1 }
2557 \new Staff { \clef bass c1 }
2561 Using a nested declaration will update the specified key (such as
2562 @code{basic-distance} in the above example) without altering any
2563 other keys already set for the same property.
2565 Now suppose we want the staves to be as close as possible without
2566 overlapping. The simplest way to do this is to set all four alist
2567 keys to zero. However, it is not necessary to enter four nested
2568 declarations, one for each key. Instead, the property can be
2569 completely re-defined with one declaration, as an alist:
2571 @lilypond[quote,verbatim]
2572 \new PianoStaff \with {
2573 \override StaffGrouper.staff-staff-spacing =
2574 #'((basic-distance . 0)
2575 (minimum-distance . 0)
2577 (stretchability . 0))
2579 \new Staff { \clef treble c''1 }
2580 \new Staff { \clef bass c1 }
2584 Note that any keys not explicitly listed in the alist definition
2585 will be reset to their @emph{default-when-unset} values. In the
2586 case of @code{staff-staff-spacing}, any unset key-values would be
2587 reset to zero (except @code{stretchability}, which takes the value
2588 of @code{basic-distance} when unset). Thus the following two
2589 declarations are equivalent:
2592 \override StaffGrouper.staff-staff-spacing =
2593 #'((basic-distance . 7))
2595 \override StaffGrouper.staff-staff-spacing =
2596 #'((basic-distance . 7)
2597 (minimum-distance . 0)
2599 (stretchability . 7))
2602 One (possibly unintended) consequence of this is the removal of
2603 any standard settings that are set in an initialization file and
2604 loaded each time an input file is compiled. In the above example,
2605 the standard settings for @code{padding} and
2606 @code{minimum-distance} (defined in @file{scm/define-grobs.scm})
2607 are reset to their default-when-unset values (zero for both keys).
2608 Defining a property or variable as an alist (of any size) will
2609 always reset all unset key-values to their default-when-unset
2610 values. Unless this is the intended result, it is safer to update
2611 key-values individually with a nested declaration.
2613 @warning{Nested declarations will not work for context property
2614 alists (such as @code{beamExceptions}, @code{keyAlterations},
2615 @code{timeSignatureSettings}, etc.). These properties can only be
2616 modified by completely re-defining them as alists.}
2619 @node Useful concepts and properties
2620 @section Useful concepts and properties
2625 * Direction and placement::
2626 * Distances and measurements::
2628 * Staff symbol properties::
2630 * Visibility of objects::
2632 * Rotating objects::
2636 @subsection Input modes
2638 The way in which the notation contained within an input file is
2639 interpreted is determined by the current input mode.
2641 @subsubsubheading Chord mode
2643 This is activated with the @code{\chordmode} command, and causes
2644 input to be interpreted with the syntax of chord notation, see
2645 @ref{Chord notation}. Chords are rendered as notes on a staff.
2647 Chord mode is also activated with the @code{\chords} command.
2648 This also creates a new @code{ChordNames} context and
2649 causes the following input to be interpreted with the syntax of
2650 chord notation and rendered as chord names in the @code{ChordNames}
2651 context, see @ref{Printing chord names}.
2653 @subsubsubheading Drum mode
2655 This is activated with the @code{\drummode} command, and causes
2656 input to be interpreted with the syntax of drum notation, see
2657 @ref{Basic percussion notation}.
2659 Drum mode is also activated with the @code{\drums} command.
2660 This also creates a new @code{DrumStaff} context and causes the
2661 following input to be interpreted with the syntax of drum notation
2662 and rendered as drum symbols on a drum staff, see
2663 @ref{Basic percussion notation}.
2665 @subsubsubheading Figure mode
2667 This is activated with the @code{\figuremode} command, and causes
2668 input to be interpreted with the syntax of figured bass, see
2669 @ref{Entering figured bass}.
2671 Figure mode is also activated with the @code{\figures} command.
2672 This also creates a new @code{FiguredBass} context and causes the
2673 following input to be interpreted with the figured bass syntax
2674 and rendered as figured bass symbols in the @code{FiguredBass}
2675 context, see @ref{Introduction to figured bass}.
2677 @subsubsubheading Fret and tab modes
2679 There are no special input modes for entering fret and tab symbols.
2681 To create tab diagrams, enter notes or chords in note mode and
2682 render them in a @code{TabStaff} context, see
2683 @ref{Default tablatures}.
2685 To create fret diagrams above a staff, you have two choices.
2686 You can either use the @code{FretBoards} context (see
2687 @ref{Automatic fret diagrams}) or you can enter them as a markup
2688 above the notes using the @code{\fret-diagram} command (see
2689 @ref{Fret diagram markups}).
2691 @subsubsubheading Lyrics mode
2693 This is activated with the @code{\lyricmode} command, and causes
2694 input to be interpreted as lyric syllables with optional durations
2695 and associated lyric modifiers, see @ref{Vocal music}.
2697 Lyric mode is also activated with the @code{\addlyrics} command.
2698 This also creates a new @code{Lyrics} context and an implicit
2699 @code{\lyricsto} command which associates the following lyrics
2700 with the preceding music.
2702 @subsubsubheading Markup mode
2704 This is activated with the @code{\markup} command, and causes
2705 input to be interpreted with the syntax of markup, see
2706 @ref{Text markup commands}.
2708 @subsubsubheading Note mode
2710 This is the default mode or it may be activated with the
2711 @code{\notemode} command. Input is interpreted as pitches,
2712 durations, markup, etc and typeset as musical notation on a staff.
2714 It is not normally necessary to specify note mode explicitly, but
2715 it may be useful to do so in certain situations, for example if you
2716 are in lyric mode, chord mode or any other mode and want to insert
2717 something that only can be done with note mode syntax.
2720 @node Direction and placement
2721 @subsection Direction and placement
2723 In typesetting music the direction and placement of many items is
2724 a matter of choice. For example, the stems of notes can
2725 be directed up or down; lyrics, dynamics, and other expressive
2726 marks may be placed above or below the staff; text may be aligned
2727 left, right or center; etc. Most of these choices may be left to
2728 be determined automatically by LilyPond, but in some cases it may
2729 be desirable to force a particular direction or placement.
2732 * Articulation direction indicators::
2733 * The direction property::
2737 @node Articulation direction indicators
2738 @unnumberedsubsubsec Articulation direction indicators
2740 By default some directions are always up or always down (e.g.,
2741 dynamics or fermata), while other things can alternate between
2742 up or down based on the stem direction (like slurs or accents).
2744 @c TODO Add table showing these
2746 The default action may be overridden by prefixing the articulation
2747 by a @emph{direction indicator}. Three direction indicators are
2748 available: @code{^} (meaning @qq{up}), @code{_} (meaning @qq{down})
2749 and @code{-} (meaning @qq{use default direction}). The direction
2750 indicator can usually be omitted, in which case @code{-} is assumed,
2751 but a direction indicator is @strong{always} required before
2754 @item @code{\tweak} commands
2755 @item @code{\markup} commands
2756 @item @code{\tag} commands
2757 @item string markups, e.g., -"string"
2758 @item fingering instructions, e.g., @w{@code{-1}}
2759 @item articulation shortcuts, e.g., @w{@code{-.}}, @w{@code{->}}, @w{@code{--}}
2762 Direction indicators affect only the next note:
2764 @lilypond[verbatim,quote]
2774 @node The direction property
2775 @unnumberedsubsubsec The direction property
2777 The position or direction of many layout objects is controlled by the
2778 @code{direction} property.
2780 The value of the @code{direction} property may be set to @code{1},
2781 meaning @qq{up} or @qq{above}, or to @w{@code{-1}}, meaning @qq{down} or
2782 @qq{below}. The symbols @code{UP} and @code{DOWN} may be used instead
2783 of @code{1} and @w{@code{-1}} respectively. The default direction may
2784 be specified by setting @code{direction} to @code{0} or @code{CENTER}.
2785 Alternatively, in many cases predefined commands exist to specify the
2786 direction. These are of the form
2789 \xxxUp, \xxxDown or \xxxNeutral
2793 where @code{\xxxNeutral} means @qq{use the default} direction.
2794 See @rlearning{Within-staff objects}.
2796 In a few cases, arpeggio for example, the value of the @code{direction}
2797 property can specify whether the object is to be placed to the right or
2798 left of the parent. In this case @w{@code{-1}} or @code{LEFT} means
2799 @qq{to the left} and @code{1} or @code{RIGHT} means @qq{to the right}.
2800 @code{0} or @code{CENTER} means @qq{use the default} direction.
2803 These all have side-axis set to #X
2804 AmbitusAccidental - direction has no effect
2806 StanzaNumber - not tried
2807 TrillPitchAccidental - not tried
2808 TrillPitchGroup - not tried
2811 These indications affect all notes until they are canceled.
2813 @lilypond[verbatim,quote]
2824 In polyphonic music, it is generally better to specify an explicit
2825 @code{voice} than change an object's direction. For more information,
2826 see @ref{Multiple voices}.
2830 @rlearning{Within-staff objects}.
2833 @ref{Multiple voices}.
2836 @node Distances and measurements
2837 @subsection Distances and measurements
2839 @cindex distances, absolute
2840 @cindex distances, scaled
2847 Distances in LilyPond are of two types: absolute and scaled.
2849 Absolute distances are used for specifying margins, indents, and
2850 other page layout details, and are by default specified in
2851 millimeters. Distances may be specified in other units by
2852 following the quantity by @code{\mm}, @code{\cm},
2853 @code{\in}@tie{}(inches), or @code{\pt}@tie{}(points, 1/72.27 of
2854 an inch). Page layout distances can also be specified in scalable
2855 units (see the following paragraph) by appending
2856 @code{\staff-space} to the quantity. Page layout is described in
2857 detail in @ref{Page layout}.
2859 Scaled distances are always specified in units of the staff-space
2860 or, rarely, the half staff-space. The staff-space is the distance
2861 between two adjacent staff lines. The default value can be changed
2862 globally by setting the global staff size, or it can be overridden
2863 locally by changing the @code{staff-space} property of
2864 @code{StaffSymbol}. Scaled distances automatically scale with any
2865 change to the either the global staff size or the
2866 @code{staff-space} property of @code{StaffSymbol}, but fonts scale
2867 automatically only with changes to the global staff size.
2868 The global staff size thus enables the overall size of a rendered
2869 score to be easily varied. For the methods of setting the global
2870 staff size see @ref{Setting the staff size}.
2874 If just a section of a score needs to be rendered to a different
2875 scale, for example an ossia section or a footnote, the global staff
2876 size cannot simply be changed as this would affect the entire score.
2877 In such cases the change in size is made by overriding both the
2878 @code{staff-space} property of @code{StaffSymbol} and the size of
2879 the fonts. A Scheme function, @code{magstep}, is available to
2880 convert from a font size change to the equivalent change in
2881 @code{staff-space}. For an explanation and an example of its use,
2882 see @rlearning{Length and thickness of objects}.
2886 @rlearning{Length and thickness of objects}.
2890 @ref{Setting the staff size}.
2894 @subsection Dimensions
2897 @cindex bounding box
2899 The dimensions of a graphical object specify the positions of the left
2900 and right edges and the bottom and top edges of the objects' bounding
2901 box as distances from the objects' reference point in units of
2902 staff-spaces. These positions are usually coded as two Scheme pairs.
2903 For example, the text markup command @code{\with-dimensions} takes
2904 three arguments, the first two of which are a Scheme pair giving the
2905 left and right edge positions and a Scheme pair giving the bottom and
2909 \with-dimensions #'(-5 . 10) #'(-3 . 15) @var{arg}
2912 This specifies a bounding box for @var{arg} with its left edge at -5,
2913 its right edge at 10, its bottom edge at -3 and its top edge at 15,
2914 all measured from the objects' reference point in units of
2919 @ref{Distances and measurements}.
2922 @node Staff symbol properties
2923 @subsection Staff symbol properties
2925 @cindex adjusting staff symbol
2926 @cindex drawing staff symbol
2927 @cindex staff symbol, setting of
2929 @c TODO Extend or remove this section. See also NR 1.6.2 Staff symbol
2930 @c Need to think of uses for these properties. Eg 'line-positions
2931 @c is used in a snippet to thicken centre line.
2932 @c If retained, add @ref to here in 1.6.2 -td
2934 The vertical position of staff lines and the number of staff lines
2935 can be defined at the same time. As the following example shows,
2936 note positions are not influenced by the staff line positions.
2938 @warning{The @code{'line-positions} property overrides the
2939 @code{'line-count} property. The number of staff lines is
2940 implicitly defined by the number of elements in the list of values
2941 for @code{'line-positions}.}
2943 @lilypond[verbatim,quote]
2945 \override StaffSymbol.line-positions = #'(7 3 0 -4 -6 -7)
2947 \relative { a4 e' f b | d1 }
2950 The width of a staff can be modified. The units are staff
2951 spaces. The spacing of objects inside the staff is not affected by
2954 @lilypond[verbatim,quote]
2956 \override StaffSymbol.width = #23
2958 \relative { a4 e' f b | d1 }
2963 @subsection Spanners
2965 Many objects of musical notation extend over several notes or even
2966 several bars. Examples are slurs, beams, tuplet brackets, volta
2967 repeat brackets, crescendi, trills, and glissandi. Such objects
2968 are collectively called @qq{spanners}, and have special properties to control
2969 their appearance and behaviour. Some of these properties are common
2970 to all spanners; others are restricted to a sub-set of the spanners.
2972 All spanners support the @code{spanner-interface}. A few, essentially
2973 those that draw a straight line between the two objects, support in
2974 addition the @code{line-spanner-interface}.
2977 * Using the spanner-interface::
2978 * Using the line-spanner-interface::
2981 @node Using the spanner-interface
2982 @unnumberedsubsubsec Using the @code{spanner-interface}
2984 This interface provides two properties that apply to several spanners.
2986 @subsubsubheading The @code{minimum-length} property
2988 The minimum length of the spanner is specified by the
2989 @code{minimum-length} property. Increasing this usually has the
2990 necessary effect of increasing the spacing of the notes between the
2991 two end points. However, this override has no effect on
2992 many spanners, as their length is determined by other considerations.
2993 A few examples where it is effective are shown below.
3003 Works as long as callback is made:
3007 Works not at all for:
3016 @lilypond[verbatim,quote,fragment]
3019 % increase the length of the tie
3020 -\tweak minimum-length #5
3024 @lilypond[verbatim,quote]
3025 \relative \compressMMRests {
3028 % increase the length of the rest bar
3029 \once \override MultiMeasureRest.minimum-length = #20
3035 @lilypond[verbatim,quote]
3038 % increase the length of the hairpin
3039 \override Hairpin.minimum-length = #20
3044 This override can also be used to increase the length of slurs and
3047 @lilypond[verbatim,quote]
3051 -\tweak minimum-length #5
3056 -\tweak minimum-length #5
3061 For some layout objects, the @code{minimum-length} property becomes
3062 effective only if the @code{set-spacing-rods} procedure is called
3063 explicitly. To do this, the @code{springs-and-rods} property should
3064 be set to @code{ly:spanner::set-spacing-rods}. For example,
3065 the minimum length of a glissando has no effect unless the
3066 @code{springs-and-rods} property is set:
3068 @lilypond[verbatim,fragment,quote]
3072 % not effective alone
3073 \once \override Glissando.minimum-length = #20
3076 % effective only when both overrides are present
3077 \once \override Glissando.minimum-length = #20
3078 \once \override Glissando.springs-and-rods = #ly:spanner::set-spacing-rods
3082 The same is true of the @code{Beam} object:
3084 @lilypond[verbatim,fragment,quote]
3085 % not effective alone
3086 \once \override Beam.minimum-length = #20
3089 % effective only when both overrides are present
3090 \once \override Beam.minimum-length = #20
3091 \once \override Beam.springs-and-rods = #ly:spanner::set-spacing-rods
3095 @subsubsubheading The @code{to-barline} property
3097 The second useful property of the @code{spanner-interface} is
3098 @code{to-barline}. By default this is true, causing hairpins and
3099 other spanners which are terminated on the first note of a measure to
3100 end instead on the immediately preceding bar line. If set to false,
3101 the spanner will extend beyond the bar line and end on the note
3104 @lilypond[verbatim,quote]
3106 a' \< a a a a \! a a a \break
3107 \override Hairpin.to-barline = ##f
3108 a \< a a a a \! a a a
3112 This property is not effective for all spanners. For example,
3113 setting it to @code{#t} has no effect on slurs or phrasing slurs
3114 or on other spanners for which terminating on the bar line would
3117 @node Using the line-spanner-interface
3118 @unnumberedsubsubsec Using the @code{line-spanner-interface}
3120 Objects which support the @code{line-spanner-interface} include
3123 @item @code{DynamicTextSpanner}
3124 @item @code{Glissando}
3125 @item @code{TextSpanner}
3126 @item @code{TrillSpanner}
3127 @item @code{VoiceFollower}
3130 The routine responsible for drawing the stencils for these spanners is
3131 @code{ly:line-spanner::print}. This routine determines the
3132 exact location of the two end points and draws a line
3133 between them, in the style requested. The locations of the two
3134 end points of the spanner are computed on-the-fly, but it is
3135 possible to override their Y-coordinates. The
3136 properties which need to be specified are nested
3137 two levels down within the property hierarchy, but the syntax of
3138 the @code{\override} command is quite simple:
3140 @lilypond[quote,fragment,verbatim]
3142 \once \override Glissando.bound-details.left.Y = #3
3143 \once \override Glissando.bound-details.right.Y = #-2
3147 The units for the @code{Y} property are @code{staff-space}s,
3148 with the center line of the staff being the zero point.
3149 For the glissando, this is the value for @code{Y} at the
3150 X-coordinate corresponding to the center point of each note head,
3151 if the line is imagined to be extended to there.
3153 If @code{Y} is not set, the value is computed from the vertical
3154 position of the corresponding attachment point of the spanner.
3156 In case of a line break, the values for the end points are
3157 specified by the @code{left-broken} and @code{right-broken}
3158 sub-lists of @code{bound-details}. For example:
3160 @lilypond[ragged-right,fragment,verbatim,quote]
3161 \override Glissando.breakable = ##t
3162 \override Glissando.bound-details.right-broken.Y = #-3
3163 c''1 \glissando \break
3168 A number of further properties of the @code{left} and
3169 @code{right} sub-lists of the @code{bound-details} property
3170 may be modified in the same way as @code{Y}:
3174 This sets the Y-coordinate of the end point, in @code{staff-space}s
3175 offset from the staff center line. By default, it is the center of
3176 the bound object, so a glissando points to the vertical center of
3179 For horizontal spanners, such as text spanners and trill spanners,
3180 it is hardcoded to 0.
3183 This determines where the line starts and ends in the X-direction,
3184 relative to the bound object. So, a value of @w{@code{-1}} (or
3185 @code{LEFT}) makes the line start/end at the left side of the note
3186 head it is attached to.
3189 This is the absolute X-coordinate of the end point. It is usually
3190 computed on the fly, and overriding it has little useful effect.
3193 Line spanners may have symbols at the beginning or end, which is
3194 contained in this sub-property. This is for internal use; it is
3195 recommended that @code{text} be used instead.
3198 This is a markup that is evaluated to yield the stencil. It is used
3199 to put @i{cresc.}, @i{tr} and other text on horizontal spanners.
3201 @lilypond[quote,ragged-right,fragment,verbatim]
3202 \override TextSpanner.bound-details.left.text
3203 = \markup { \small \bold Slower }
3204 \relative { c''2\startTextSpan b c a\stopTextSpan }
3207 @item stencil-align-dir-y
3208 @item stencil-offset
3209 Without setting one of these, the stencil is simply put at the
3210 end-point, centered on the line, as defined by the @code{X} and
3211 @code{Y} sub-properties. Setting either @code{stencil-align-dir-y}
3212 or @code{stencil-offset} will move the symbol at the edge vertically
3213 relative to the end point of the line:
3215 @lilypond[quote,fragment,verbatim]
3216 \override TextSpanner.bound-details.left.stencil-align-dir-y = #-2
3217 \override TextSpanner.bound-details.right.stencil-align-dir-y = #UP
3219 \override TextSpanner.bound-details.left.text = #"ggg"
3220 \override TextSpanner.bound-details.right.text = #"hhh"
3222 \relative { c'4^\startTextSpan c c c \stopTextSpan }
3225 Note that negative values move the text @emph{up}, contrary to the
3226 effect that might be expected, as a value of @w{@code{-1}} or
3227 @code{DOWN} means align the @emph{bottom} edge of the text with
3228 the spanner line. A value of @code{1} or @code{UP} aligns
3229 the top edge of the text with the spanner line.
3232 Setting this sub-property to @code{#t} produces an arrowhead at the
3233 end-points of the line.
3236 This sub-property controls the space between the specified
3237 end point of the line and the actual end. Without padding, a
3238 glissando would start and end in the center of each note head.
3242 The music function @code{\endSpanners} terminates the spanner
3243 which starts on the immediately following note prematurely. It
3244 is terminated after exactly one note, or at the following bar line
3245 if @code{to-barline} is true and a bar line occurs before the next
3248 @lilypond[verbatim,quote,ragged-right]
3251 c2 \startTextSpan c2 c2
3257 When using @code{\endSpanners} it is not necessary to close
3258 \startTextSpan with \stopTextSpan, nor is it necessary to close
3259 hairpins with @code{\!}.
3262 Internals Reference:
3263 @rinternals{TextSpanner},
3264 @rinternals{Glissando},
3265 @rinternals{VoiceFollower},
3266 @rinternals{TrillSpanner},
3267 @rinternals{line-spanner-interface}.
3270 @node Visibility of objects
3271 @subsection Visibility of objects
3273 @cindex objects, visibility of
3274 @cindex grobs, visibility of
3275 @cindex visibility of objects
3277 There are four main ways in which the visibility of layout objects
3278 can be controlled: their stencil can be removed, they can be made
3279 transparent, they can be colored white, or their
3280 @code{break-visibility} property can be overridden. The first
3281 three apply to all layout objects; the last to just a few -- the
3282 @emph{breakable} objects. The Learning Manual introduces these
3283 four techniques, see @rlearning{Visibility and color of objects}.
3285 There are also a few other techniques which are specific to
3286 certain layout objects. These are covered under Special
3290 * Removing the stencil::
3291 * Making objects transparent::
3292 * Painting objects white::
3293 * Using break-visibility::
3294 * Special considerations::
3298 @node Removing the stencil
3299 @unnumberedsubsubsec Removing the stencil
3301 @cindex stencil, removing
3304 Every layout object has a stencil property. By default this is set
3305 to the specific function which draws that object. If this property
3306 is overridden to @code{#f} no function will be called and the object
3307 will not be drawn. The default action can be recovered with
3310 @lilypond[quote,fragment,verbatim]
3312 \override Score.BarLine.stencil = ##f
3314 \revert Score.BarLine.stencil
3318 This rather common operation has a shortcut @code{\omit}:
3320 @lilypond[quote,fragment,verbatim]
3324 \undo \omit Score.BarLine
3328 @node Making objects transparent
3329 @unnumberedsubsubsec Making objects transparent
3331 @cindex transparent, making objects
3334 Every layout object has a transparent property which by default is
3335 set to @code{#f}. If set to @code{#t} the object still occupies
3336 space but is made invisible.
3338 @lilypond[quote,fragment,verbatim]
3340 \once \override NoteHead.transparent = ##t
3344 This rather common operation has a shortcut @code{\hide}:
3346 @lilypond[quote,fragment,verbatim]
3348 \once \hide NoteHead
3352 @node Painting objects white
3353 @unnumberedsubsubsec Painting objects white
3355 @cindex objects, coloring
3356 @cindex coloring objects
3358 @cindex printing order
3359 @cindex overwriting objects
3360 @cindex objects, overwriting
3361 @cindex grobs, overwriting
3363 Every layout object has a color property which by default is set
3364 to @code{black}. If this is overridden to @code{white} the object
3365 will be indistinguishable from the white background. However,
3366 if the object crosses other objects the color of the crossing
3367 points will be determined by the order in which they are drawn,
3368 and this may leave a ghostly image of the white object, as shown
3371 @lilypond[quote,fragment,verbatim]
3372 \override Staff.Clef.color = #white
3376 This may be avoided by changing the order of printing the objects.
3377 All layout objects have a @code{layer} property which should be set
3378 to an integer. Objects with the lowest value of @code{layer} are
3379 drawn first, then objects with progressively higher values are drawn,
3380 so objects with higher values overwrite objects with lower values.
3381 By default most objects are assigned a @code{layer} value of
3382 @code{1}, although a few objects, including @code{StaffSymbol} and
3383 @code{BarLine}, are assigned a value of @code{0}. The order of
3384 printing objects with the same value of @code{layer} is indeterminate.
3386 In the example above the white clef, with a default @code{layer}
3387 value of @code{1}, is drawn after the staff lines (default
3388 @code{layer} value @code{0}), so overwriting them. To change this,
3389 the @code{Clef} object must be given in a lower value of
3390 @code{layer}, say @w{@code{-1}}, so that it is drawn earlier:
3392 @lilypond[quote,fragment,verbatim]
3393 \override Staff.Clef.color = #white
3394 \override Staff.Clef.layer = #-1
3398 @node Using break-visibility
3399 @unnumberedsubsubsec Using break-visibility
3401 @c TODO Add making other objects breakable
3403 @cindex break-visibility
3405 Most layout objects are printed only once, but some like
3406 bar lines, clefs, time signatures and key signatures, may need
3407 to be printed twice when a line break occurs -- once at the end
3408 of the line and again at the start of the next line. Such
3409 objects are called @emph{breakable}, and have a property, the
3410 @code{break-visibility} property to control their visibility
3411 at the three positions in which they may appear -- at the
3412 start of a line, within a line if they are changed, and at the
3413 end of a line if a change takes place there.
3415 For example, the time signature
3416 by default will be printed at the start of the first line, but
3417 nowhere else unless it changes, when it will be printed at the
3418 point at which the change occurs. If this change occurs at the
3419 end of a line the new time signature will be printed at the start
3420 of the next line and a cautionary time signature will be printed
3421 at the end of the previous line as well.
3423 This behaviour is controlled by the @code{break-visibility}
3424 property, which is explained in
3425 @c Leave this ref on a newline - formats incorrectly otherwise -td
3426 @rlearning{Visibility and color of objects}. This property takes
3427 a vector of three booleans which, in order, determine whether the
3428 object is printed at the end of, within the body of, or at the
3429 beginning of a line. Or to be more precise, before a line break,
3430 where there is no line break, or after a line break.
3432 Alternatively, these eight combinations may be specified
3433 by pre-defined functions, defined in @file{scm/output-lib.scm},
3434 where the last three columns indicate whether the layout objects
3435 will be visible in the positions shown at the head of the columns:
3437 @multitable {@code{begin-of-line-invisible}} {@code{#(#t #t #t)}} {Before} {At no} {After}
3438 @headitem Function @tab Vector @tab Before @tab At no @tab After
3439 @headitem form @tab form @tab break @tab break @tab break
3441 @item @code{all-visible} @tab @code{#(#t #t #t)} @tab yes @tab yes @tab yes
3442 @item @code{begin-of-line-visible} @tab @code{#(#f #f #t)} @tab no @tab no @tab yes
3443 @item @code{center-visible} @tab @code{#(#f #t #f)} @tab no @tab yes @tab no
3444 @item @code{end-of-line-visible} @tab @code{#(#t #f #f)} @tab yes @tab no @tab no
3445 @item @code{begin-of-line-invisible} @tab @code{#(#t #t #f)} @tab yes @tab yes @tab no
3446 @item @code{center-invisible} @tab @code{#(#t #f #t)} @tab yes @tab no @tab yes
3447 @item @code{end-of-line-invisible} @tab @code{#(#f #t #t)} @tab no @tab yes @tab yes
3448 @item @code{all-invisible} @tab @code{#(#f #f #f)} @tab no @tab no @tab no
3451 The default settings of @code{break-visibility} depend on the
3452 layout object. The following table shows all the layout objects
3453 of interest which are affected by @code{break-visibility} and the
3454 default setting of this property:
3456 @multitable @columnfractions .3 .3 .4
3458 @headitem Layout object @tab Usual context @tab Default setting
3460 @c omit Ambitus as it appears not to be affected by break-visibility -td
3461 @c @item @code{Ambitus} @tab as specified @tab @code{begin-of-line-visible}
3462 @item @code{BarLine} @tab @code{Score} @tab calculated
3463 @item @code{BarNumber} @tab @code{Score} @tab @code{begin-of-line-visible}
3464 @c omit the following item until it can be explained -td
3465 @c @item @code{BreakAlignGroup} @tab @code{Score} @tab calculated
3466 @item @code{BreathingSign} @tab @code{Voice} @tab @code{begin-of-line-invisible}
3467 @item @code{Clef} @tab @code{Staff} @tab @code{begin-of-line-visible}
3468 @item @code{Custos} @tab @code{Staff} @tab @code{end-of-line-visible}
3469 @item @code{DoublePercentRepeat} @tab @code{Voice} @tab @code{begin-of-line-invisible}
3470 @item @code{KeyCancellation} @tab @code{Staff} @tab @code{begin-of-line-invisible}
3471 @item @code{KeySignature} @tab @code{Staff} @tab @code{begin-of-line-visible}
3472 @c omit LeftEdge until it can be explained -td
3473 @c @item @code{LeftEdge} @tab @code{Score} @tab @code{center-invisible}
3474 @item @code{ClefModifier} @tab @code{Staff} @tab @code{begin-of-line-visible}
3475 @item @code{RehearsalMark} @tab @code{Score} @tab @code{end-of-line-invisible}
3476 @item @code{TimeSignature} @tab @code{Staff} @tab @code{all-visible}
3480 The example below shows the use of the vector form to control the
3481 visibility of bar lines:
3483 @lilypond[quote,verbatim,ragged-right]
3487 % Remove bar line at the end of the current line
3488 \once \override Score.BarLine.break-visibility = ##(#f #t #t)
3495 Although all three components of the vector used to override
3496 @code{break-visibility} must be present, not all of them are
3497 effective with every layout object, and some combinations may
3498 even give errors. The following limitations apply:
3501 @item Bar lines cannot be printed at the start of line.
3503 @item A bar number cannot be printed at the start of the @emph{first}
3504 line unless it is set to be different from @code{1}.
3506 @item Clef -- see the next section.
3508 @item Double percent repeats are either @emph{all printed} or
3509 @emph{all suppressed}. Use @code{begin-of-line-invisible}
3510 to print them and @code{all-invisible} to suppress them.
3512 @item Key signature -- see the next section.
3514 @item ClefModifier -- see the next section.
3518 @node Special considerations
3519 @unnumberedsubsubsec Special considerations
3521 @subsubsubheading Visibility following explicit changes
3523 @cindex key signature, visibility following explicit change
3524 @cindex explicitKeySignatureVisibility
3525 @cindex clef, visibility following explicit change
3526 @cindex explicitClefVisibility
3528 The @code{break-visibility} property controls the visibility of
3529 key signatures and changes of clef only at the start of lines,
3530 i.e., after a break. It has no effect on the visibility of the
3531 key signature or clef following an explicit key change or an
3532 explicit clef change within or at the end of a line. In the
3533 following example the key signature following the explicit change
3534 to B-flat major is still visible, even though @code{all-invisible}
3537 @lilypond[quote,verbatim,ragged-right]
3541 % Try to remove all key signatures
3542 \override Staff.KeySignature.break-visibility = #all-invisible
3551 The visibility of such explicit key signature and clef changes is
3552 controlled by the @code{explicitKeySignatureVisibility} and
3553 @code{explicitClefVisibility} properties. These are the equivalent
3554 of the @code{break-visibility} property and both take a vector of
3555 three booleans or the predefined functions listed above, exactly like
3556 @code{break-visibility}. Both are properties of the Staff context,
3557 not the layout objects themselves, and so they are set using the
3558 @code{\set} command. Both are set by default to @code{all-visible}.
3559 These properties control only the visibility of key signatures and
3560 clefs resulting from explicit changes and do not affect key
3561 signatures and clefs at the beginning of lines;
3562 @code{break-visibility} must still be overridden in the appropriate
3563 object to remove these.
3565 @lilypond[quote,verbatim,ragged-right]
3569 \set Staff.explicitKeySignatureVisibility = #all-invisible
3570 \override Staff.KeySignature.break-visibility = #all-invisible
3578 @subsubsubheading Visibility of cancelling accidentals
3580 To remove the cancelling accidentals printed at an explicit key
3581 change, set the Staff context property @code{printKeyCancellation}
3584 @lilypond[quote,verbatim,ragged-right]
3588 \set Staff.explicitKeySignatureVisibility = #all-invisible
3589 \set Staff.printKeyCancellation = ##f
3590 \override Staff.KeySignature.break-visibility = #all-invisible
3598 With these overrides only the accidentals before the notes remain
3599 to indicate the change of key.
3601 Note that when changing the key to C@tie{}major or A@tie{}minor
3602 the cancelling accidentals would be the @emph{only} indication of
3603 the key change. In this case setting @code{printKeyCancellation} to
3604 @code{#f} has no effect:
3606 @lilypond[quote,verbatim,ragged-right]
3610 \set Staff.explicitKeySignatureVisibility = #all-invisible
3611 \set Staff.printKeyCancellation = ##f
3619 To suppress the cancelling accidentals even when the key is
3620 changed to C@tie{}major or A@tie{}minor, override
3621 the visibility of the @code{KeyCancellation} grob instead:
3623 @lilypond[quote,verbatim,ragged-right]
3627 \set Staff.explicitKeySignatureVisibility = #all-invisible
3628 \override Staff.KeyCancellation.break-visibility = #all-invisible
3636 @c TODO Add visibility of cautionary accidentals before notes
3638 @subsubsubheading Automatic bars
3640 @cindex automaticBars
3641 @cindex bar lines, suppressing
3643 As a special case, the printing of bar lines can also be turned off
3644 by setting the @code{automaticBars} property in the Score context.
3645 If set to @code{#f}, bar lines will not be printed automatically;
3646 they must be explicitly created with a @code{\bar} command. Unlike
3647 the @code{\cadenzaOn} predefined command, measures are still counted.
3648 Bar generation will resume according to that count if this property
3649 is later set to @code{#t}. When set to @code{#f}, line breaks can
3650 occur only at explicit @code{\bar} commands.
3654 @subsubsubheading Transposed clefs
3656 @cindex transposed clefs, visibility of
3657 @cindex visibility of transposed clefs
3658 @cindex clefs, visibility of transposition
3660 The small transposition symbol on transposed clefs is produced by the
3661 @code{ClefModifier} layout object. Its visibility is automatically
3662 inherited from the @code{Clef} object, so it is not necessary to apply
3663 any required @code{break-visibility} overrides to the @code{ClefModifier}
3664 layout objects to suppress transposition symbols for invisible clefs.
3666 For explicit clef changes, the @code{explicitClefVisibility}
3667 property controls both the clef symbol and any transposition symbol
3672 @rlearning{Visibility and color of objects}.
3676 @subsection Line styles
3678 Some performance indications, e.g., @i{rallentando} and
3679 @i{accelerando} and @i{trills} are written as text and are
3680 extended over many measures with lines, sometimes dotted or wavy.
3682 These all use the same routines as the glissando for drawing the
3683 texts and the lines, and tuning their behavior is therefore also
3684 done in the same way. It is done with a spanner, and the routine
3685 responsible for drawing the spanners is
3686 @code{ly:line-spanner::print}. This routine determines the
3687 exact location of the two @i{span points} and draws a line
3688 between them, in the style requested.
3690 Here is an example showing the different line styles available,
3691 and how to tune them.
3693 @lilypond[ragged-right,verbatim,quote]
3696 \once \override Glissando.style = #'dashed-line
3698 \override Glissando.style = #'dotted-line
3700 \override Glissando.style = #'zigzag
3702 \override Glissando.style = #'trill
3707 The locations of the end-points of the spanner are computed
3708 on-the-fly for every graphic object, but it is possible to
3712 @lilypond[ragged-right,verbatim,quote]
3715 \once \override Glissando.bound-details.right.Y = #-2
3720 The value for @code{Y} is set to @w{@code{-2}} for the right end
3721 point. The left side may be similarly adjusted by specifying
3722 @code{left} instead of @code{right}.
3724 If @code{Y} is not set, the value is computed from the vertical
3725 position of the left and right attachment points of the spanner.
3727 Other adjustments of spanners are possible, for details, see
3730 @node Rotating objects
3731 @subsection Rotating objects
3733 Both layout objects and elements of markup text can be rotated by
3734 any angle about any point, but the method of doing so differs.
3737 * Rotating layout objects::
3741 @node Rotating layout objects
3742 @unnumberedsubsubsec Rotating layout objects
3744 @cindex rotating objects
3745 @cindex objects, rotating
3747 All layout objects which support the @code{grob-interface} can be
3748 rotated by setting their @code{rotation} property. This takes a
3749 list of three items: the angle of rotation counter-clockwise,
3750 and the x and y coordinates of the point relative to the object's
3751 reference point about which the rotation is to be performed. The
3752 angle of rotation is specified in degrees and the coordinates in
3755 The angle of rotation and the coordinates of the rotation point must
3756 be determined by trial and error.
3758 @cindex hairpins, angled
3759 @cindex angled hairpins
3761 There are only a few situations where the rotation of layout
3762 objects is useful; the following example shows one situation where
3765 @lilypond[quote,fragment,verbatim]
3767 \override Hairpin.rotation = #'(20 -1 0)
3771 @node Rotating markup
3772 @unnumberedsubsubsec Rotating markup
3774 All markup text can be rotated to lie at any angle by prefixing it
3775 with the @code{\rotate} command. The command takes two arguments:
3776 the angle of rotation in degrees counter-clockwise and the text to
3777 be rotated. The extents of the text are not rotated: they take
3778 their values from the extremes of the x and y coordinates of the
3779 rotated text. In the following example the
3780 @code{outside-staff-priority} property for text is set to @code{#f}
3781 to disable the automatic collision avoidance, which would push some
3782 of the text too high.
3784 @lilypond[quote,fragment,verbatim]
3785 \override TextScript.outside-staff-priority = ##f
3786 g4^\markup { \rotate #30 "a G" }
3787 b^\markup { \rotate #30 "a B" }
3788 des'^\markup { \rotate #30 "a D-Flat" }
3789 fis'^\markup { \rotate #30 "an F-Sharp" }
3792 @node Advanced tweaks
3793 @section Advanced tweaks
3795 This section discusses various approaches to fine tuning the
3796 appearance of the printed score.
3799 * Aligning objects::
3800 * Vertical grouping of grobs::
3801 * Modifying stencils::
3802 * Modifying shapes::
3803 * Modifying broken spanners::
3804 * Unpure-pure containers::
3809 @rlearning{Tweaking output},
3810 @rlearning{Other sources of information}.
3813 @ref{Explaining the Internals Reference},
3814 @ref{Modifying properties}.
3817 @rextend{Interfaces for programmers}.
3820 @file{scm/define-grobs.scm}.
3823 @rlsr{Tweaks and overrides}.
3825 Internals Reference:
3826 @rinternals{All layout objects}.
3829 @node Aligning objects
3830 @subsection Aligning objects
3832 Graphical objects which support the @code{self-alignment-interface}
3833 and/or the @code{side-position-interface} can be aligned to a previously
3834 placed object in a variety of ways. For a list of these objects, see
3835 @rinternals{self-alignment-interface} and @rinternals{side-position-interface}.
3837 All graphical objects have a reference point, a horizontal extent and a
3838 vertical extent. The horizontal extent is a pair of numbers
3839 giving the displacements from the reference point of the left and
3840 right edges, displacements to the left being negative. The vertical
3841 extent is a pair of numbers giving the displacement from the reference
3842 point to the bottom and top edges, displacements down being negative.
3844 An object's position on a staff is given by the values of the
3845 @code{X-offset} and @code{Y-offset} properties. The value of
3846 @code{X-offset} gives the displacement from the X coordinate of
3847 the reference point of the parent object, and the value of
3848 @code{Y-offset} gives the displacement from the center line of the
3849 staff. The values of @code{X-offset} and @code{Y-offset} may
3850 be set directly or may be set to be calculated by procedures in order
3851 to achieve alignment with the parent object.
3853 @warning{Many objects have special positioning considerations which
3854 cause any setting of @code{X-offset} or @code{Y-offset} to be
3855 ignored or modified, even though the object supports the
3856 @code{self-alignment-interface}. Overriding the @code{X-offset}
3857 or @code{Y-offset} properties to a fixed value causes the respective
3858 @code{self-alignment} property to be disregarded.}
3860 For example, an accidental can be repositioned vertically by setting
3861 @code{Y-offset} but any changes to @code{X-offset} have no effect.
3863 Rehearsal marks may be aligned with breakable objects such as bar
3864 lines, clef symbols, time signature symbols and key signatures. There
3865 are special properties to be found in the @code{break-aligned-interface}
3866 for positioning rehearsal marks on such objects.
3870 @ref{Using the break-alignable-interface}.
3873 @rextend{Callback functions}.
3876 * Setting X-offset and Y-offset directly::
3877 * Using the side-position-interface::
3878 * Using the self-alignment-interface::
3879 * Using the break-alignable-interface::
3882 @node Setting X-offset and Y-offset directly
3883 @unnumberedsubsubsec Setting @code{X-offset} and @code{Y-offset} directly
3885 Numerical values may be given to the @code{X-offset} and @code{Y-offset}
3886 properties of many objects. The following example shows three
3887 notes with the default fingering position and the positions with @code{X-offset}
3888 and @code{Y-offset} modified.
3890 @lilypond[verbatim,fragment,quote]
3897 -\tweak X-offset #-1
3904 @node Using the side-position-interface
3905 @unnumberedsubsubsec Using the @code{side-position-interface}
3907 An object which supports the @code{side-position-interface} can be
3908 placed next to its parent object so that
3909 the specified edges of the two objects touch. The object may be
3910 placed above, below, to the right or to the left of the parent.
3911 The parent cannot be specified; it is determined by the order of
3912 elements in the input stream. Most objects have the associated
3913 note head as their parent.
3915 The values of the @code{side-axis} and @code{direction} properties
3916 determine where the object is to be placed, as follows:
3918 @c TODO add an example of each to the table
3920 @multitable @columnfractions .3 .3 .3
3921 @headitem @code{side-axis} @tab @code{direction} @tab
3922 @headitem property @tab property @tab Placement
3924 @item @code{0} @tab @code{-1} @tab left
3925 @item @code{0} @tab @code{1} @tab right
3926 @item @code{1} @tab @code{-1} @tab below
3927 @item @code{1} @tab @code{1} @tab above
3931 When @code{side-axis} is @code{0}, @code{X-offset} should be set to
3932 the procedure @code{ly:side-position-interface::x-aligned-side}.
3933 This procedure will return the correct value of @code{X-offset} to
3934 place the object to the left or right side of the parent according
3935 to value of @code{direction}.
3937 When @code{side-axis} is @code{1}, @code{Y-offset} should be set to
3938 the procedure @code{ly:side-position-interface::y-aligned-side}.
3939 This procedure will return the correct value of @code{Y-offset} to
3940 place the object to the top or bottom of the parent according
3941 to value of @code{direction}.
3943 @c TODO Add examples
3945 @node Using the self-alignment-interface
3946 @unnumberedsubsubsec Using the @code{self-alignment-interface}
3948 @subsubsubheading Self-aligning objects horizontally
3950 The horizontal alignment of an object which supports the
3951 @code{self-alignment-interface} is controlled by the value of
3952 the @code{self-alignment-X} property, provided the object's
3953 @code{X-offset} property is set to
3954 @code{ly:self-alignment-interface::x-aligned-on-self}.
3955 @code{self-alignment-X} may be given any
3956 real value, in units of half the total X extent of the
3957 object. Negative values move the object to the right, positive
3958 to the left. A value of @code{0} centers the object on the
3959 reference point of its parent, a value of @w{@code{-1}} aligns the
3960 left edge of the object on the reference point of its parent,
3961 and a value of @code{1} aligns the right edge of the object on the
3962 reference point of its parent. The symbols @code{LEFT},
3963 @code{CENTER}, and @code{RIGHT} may be used instead of the values
3964 @w{@code{-1}}, @code{0}, and @code{1}, respectively.
3966 Normally the @code{\override} command would be used to modify the
3967 value of @code{self-alignment-X}, but the @code{\tweak} command
3968 can be used to separately align several annotations on a single
3971 @lilypond[quote,verbatim,fragment]
3973 -\tweak self-alignment-X #-1
3975 -\tweak self-alignment-X #0
3977 -\tweak self-alignment-X #RIGHT
3979 -\tweak self-alignment-X #-2.5
3980 ^"aligned further to the right"
3983 @subsubsubheading Self-aligning objects vertically
3985 Objects may be aligned vertically in an analogous way to aligning
3986 them horizontally if the @code{Y-offset} property is set to
3987 @code{ly:self-alignment-interface::y-aligned-on-self}. However,
3988 other mechanisms are often involved in vertical alignment: the
3989 value of @code{Y-offset} is just one variable taken into account.
3990 This may make adjusting the value of some objects tricky.
3991 The units are just half the vertical extent of the object, which
3992 is usually quite small, so quite large numbers may be required.
3993 A value of @w{@code{-1}} aligns the lower edge of the object with
3994 the reference point of the parent object, a value of @code{0}
3995 aligns the center of the object with the reference point of the
3996 parent, and a value of @code{1} aligns the top edge of the object
3997 with the reference point of the parent. The symbols @code{DOWN},
3998 @code{CENTER}, and @code{UP} may be substituted for @w{@code{-1}},
3999 @code{0}, and @code{1}, respectively.
4001 @subsubsubheading Self-aligning objects in both directions
4003 By setting both @code{X-offset} and @code{Y-offset}, an object may
4004 be aligned in both directions simultaneously.
4006 The following example shows how to adjust a fingering mark so
4007 that it nestles close to the note head.
4009 @lilypond[quote,verbatim,fragment]
4011 -\tweak self-alignment-X #0.5 % move horizontally left
4012 -\tweak Y-offset #ly:self-alignment-interface::y-aligned-on-self
4013 -\tweak self-alignment-Y #-1 % move vertically up
4018 @unnumberedsubsubsec Using the @code{aligned-on-parent} procedures
4020 @c Cannot document as they do not seem to operate consistently on all objects -td
4021 @c TODO investigate further
4023 The @code{aligned-on-parent} procedures are used in the same way
4024 as the @code{aligned-on-self} procedures, they difference being
4025 that they permit an object to be aligned with the @emph{edges} of
4026 the parent rather than the parent's reference point. The following
4027 example shows the difference:
4031 @lilypond[verbatim,quote]
4037 @unnumberedsubsubsec Using the @code{centered-on-parent} procedures
4039 @c Cannot document as they do not seem to operate consistently on all objects -td
4040 @c TODO investigate further
4044 @c TODO The align-interface, BassFigureAlignment and VerticalAlignment
4046 @node Using the break-alignable-interface
4047 @unnumberedsubsubsec Using the @code{break-alignable-interface}
4049 @cindex align to objects
4050 @cindex break-align-symbols
4052 Rehearsal marks and bar numbers may be aligned with notation
4053 objects other than bar lines. These objects include @code{ambitus},
4054 @code{breathing-sign}, @code{clef}, @code{custos}, @code{staff-bar},
4055 @code{left-edge}, @code{key-cancellation}, @code{key-signature}, and
4056 @code{time-signature}.
4058 Each type of object has its own default reference point, to which
4059 rehearsal marks are aligned:
4061 @lilypond[verbatim,quote,fragment]
4062 % The rehearsal mark will be aligned to the right edge of the Clef
4063 \override Score.RehearsalMark.break-align-symbols = #'(clef)
4068 % The rehearsal mark will be aligned to the left edge of the Time Signature
4069 \override Score.RehearsalMark.break-align-symbols = #'(time-signature)
4075 % The rehearsal mark will be centered above the Breath Mark
4076 \override Score.RehearsalMark.break-align-symbols = #'(breathing-sign)
4085 A list of possible target alignment objects may be specified. If
4086 some of the objects are invisible at that point due to the setting
4087 of @code{break-visibility} or the explicit visibility settings for
4088 keys and clefs, the rehearsal mark or bar number is aligned to the
4089 first object in the list which is visible. If no objects in the
4090 list are visible the object is aligned to the bar line. If the bar
4091 line is invisible the object is aligned to the place where the bar
4094 @lilypond[verbatim,quote,fragment]
4095 % The rehearsal mark will be aligned to the right edge of the Key Signature
4096 \override Score.RehearsalMark.break-align-symbols = #'(key-signature clef)
4101 % The rehearsal mark will be aligned to the right edge of the Clef
4102 \set Staff.explicitKeySignatureVisibility = #all-invisible
4103 \override Score.RehearsalMark.break-align-symbols = #'(key-signature clef)
4108 % The rehearsal mark will be centered above the Bar Line
4109 \set Staff.explicitKeySignatureVisibility = #all-invisible
4110 \set Staff.explicitClefVisibility = #all-invisible
4111 \override Score.RehearsalMark.break-align-symbols = #'(key-signature clef)
4118 The alignment of the rehearsal mark relative to the notation object
4119 can be changed, as shown in the following example. In a score with
4120 multiple staves, this setting should be done for all the staves.
4122 @lilypond[verbatim,quote,fragment]
4123 % The RehearsalMark will be aligned with the right edge of the Key Signature
4124 \override Score.RehearsalMark.break-align-symbols = #'(key-signature)
4130 % The RehearsalMark will be centered above the Key Signature
4131 \once \override Score.KeySignature.break-align-anchor-alignment = #CENTER
4135 % The RehearsalMark will be aligned with the left edge of the Key Signature
4136 \once \override Score.KeySignature.break-align-anchor-alignment = #LEFT
4142 The rehearsal mark can also be offset to the right or left of the left
4143 edge by an arbitrary amount. The units are staff-spaces:
4145 @lilypond[verbatim,quote,fragment]
4146 % The RehearsalMark will be aligned with the left edge of the Key Signature
4147 % and then shifted right by 3.5 staff-spaces
4148 \override Score.RehearsalMark.break-align-symbols = #'(key-signature)
4149 \once \override Score.KeySignature.break-align-anchor = #3.5
4153 % The RehearsalMark will be aligned with the left edge of the Key Signature
4154 % and then shifted left by 2 staff-spaces
4155 \once \override Score.KeySignature.break-align-anchor = #-2
4162 @node Vertical grouping of grobs
4163 @subsection Vertical grouping of grobs
4165 @c TODO Expand this section
4167 The VerticalAlignment and VerticalAxisGroup grobs work together.
4168 VerticalAxisGroup groups together different grobs like Staff, Lyrics,
4169 etc. VerticalAlignment then vertically aligns the different grobs
4170 grouped together by VerticalAxisGroup. There is usually only one
4171 VerticalAlignment per score but every Staff, Lyrics, etc., has its own
4175 @node Modifying stencils
4176 @subsection Modifying stencils
4178 All layout objects have a @code{stencil} property which is part of
4179 the @code{grob-interface}. By default, this property is usually
4180 set to a function specific to the object that is tailor-made to
4181 render the symbol which represents it in the output. For example,
4182 the standard setting for the @code{stencil} property of the
4183 @code{MultiMeasureRest} object is @code{ly:multi-measure-rest::print}.
4185 The standard symbol for any object can be replaced by modifying the
4186 @code{stencil} property to reference a different, specially-written,
4187 procedure. This requires a high level of knowledge of the internal
4188 workings of LilyPond, but there is an easier way which can often
4189 produce adequate results.
4191 This is to set the @code{stencil} property to the procedure which
4192 prints text -- @code{ly:text-interface::print} -- and to add a
4193 @code{text} property to the object which is set to contain the
4194 markup text which produces the required symbol. Due to the
4195 flexibility of markup, much can be achieved -- see in particular
4196 @ref{Graphic notation inside markup}.
4198 The following example demonstrates this by changing the note head
4199 symbol to a cross within a circle.
4201 @lilypond[verbatim,quote]
4203 \once \override NoteHead.stencil = #ly:text-interface::print
4204 \once \override NoteHead.text = \markup {
4206 \halign #-0.7 \draw-circle #0.85 #0.2 ##f
4207 \musicglyph #"noteheads.s2cross"
4215 Any of the glyphs in the Feta Font can be supplied to the
4216 @code{\musicglyph} markup command -- see @ref{The Feta font}.
4218 @file{EPS} files and Postscript commands can both be inserted inline
4219 using the @code{\epsfile} and @code{\postscript} markup commands
4220 respectively -- see @ref{Graphic}.
4225 @ref{Graphic notation inside markup},
4226 @ref{Formatting text},
4227 @ref{Text markup commands},
4228 @ref{The Feta font},
4232 @node Modifying shapes
4233 @subsection Modifying shapes
4236 * Modifying ties and slurs::
4239 @node Modifying ties and slurs
4240 @unnumberedsubsubsec Modifying ties and slurs
4242 @cindex slurs, modifying
4243 @cindex ties, modifying
4244 @cindex Bézier curves, control points
4245 @cindex control points, Bézier curves
4247 @code{Tie}s, @code{Slur}s, @code{PhrasingSlur}s,
4248 @code{LaissezVibrerTie}s and @code{RepeatTie}s are all drawn as
4249 third-order Bézier curves. If the shape of the tie or slur which
4250 is calculated automatically is not optimum, the shape may be
4251 modified manually in two ways:
4255 by specifying the displacements to be made to the control points
4256 of the automatically calculated Bézier curve, or
4259 by explicitly specifying the positions of the four control points
4260 required to define the wanted curve.
4263 Both methods are explained below. The first method is more suitable
4264 if only slight adjustments to the curve are required; the second may
4265 be better for creating curves which are related to just a single
4268 @subsubsubheading Cubic Bézier curves
4270 Third-order or cubic Bézier curves are defined by four control
4271 points. The first and fourth control points are precisely the
4272 starting and ending points of the curve. The intermediate two
4273 control points define the shape. Animations showing how the curve
4274 is drawn can be found on the web, but the following description
4275 may be helpful. The curve starts from the first control point
4276 heading directly towards the second, gradually bending over to
4277 head towards the third and continuing to bend over to head towards
4278 the fourth, arriving there travelling directly from the third
4279 control point. The curve is entirely contained in the
4280 quadrilateral defined by the four control points. Translations,
4281 rotations and scaling of the control points all result in exactly
4282 the same operations on the curve.
4284 @subsubsubheading Specifying displacements from current control points
4286 @cindex shaping slurs and ties
4289 In this example the automatic placement of the tie is not optimum,
4290 and @code{\tieDown} would not help.
4292 @lilypond[verbatim,quote]
4296 \relative { r4 <g' c,> <g c,> <g c,> }
4300 Adjusting the control points of the tie with @code{\shape} allows
4301 the collisions to be avoided.
4303 The syntax of @code{\shape} is
4306 [-]\shape @var{displacements} @var{item}
4309 This will reposition the control-points of @var{item} by the amounts
4310 given by @var{displacements}. The @var{displacements} argument is a
4311 list of number pairs or a list of such lists. Each element of a pair
4312 represents the displacement of one of the coordinates of a
4313 control-point. If @var{item} is a string, the result is
4314 @code{\once\override} for the specified grob type. If @var{item} is
4315 a music expression, the result is the same music expression with an
4316 appropriate tweak applied.
4318 In other words, the @code{\shape} function can act as either a
4319 @code{\once\override} command or a @code{\tweak} command depending
4320 on whether the @var{item} argument is a grob name, like @qq{Slur},
4321 or a music expression, like @qq{(}. The @var{displacements} argument
4322 specifies the displacements of the four control points as a list of
4323 four pairs of (dx . dy) values in units of staff-spaces (or a list
4324 of such lists if the curve has more than one segment).
4326 The leading hyphen is required if and only if the @code{\tweak} form
4329 So, using the same example as above and the @code{\once\override}
4330 form of @code{\shape}, this will raise the tie by half a staff-space:
4332 @lilypond[verbatim,quote]
4335 \shape #'((0 . 0.5) (0 . 0.5) (0 . 0.5) (0 . 0.5)) Tie
4339 \relative { r4 <g' c,> <g c,> <g c,> }
4343 This positioning of the tie is better, but maybe it should be raised
4344 more in the center. The following example does this, this time using
4345 the alternative @code{\tweak} form:
4347 @lilypond[verbatim,quote]
4350 e'1-\shape #'((0 . 0.5) (0 . 1) (0 . 1) (0 . 0.5)) ~ e'
4353 \relative { r4 <g' c,> <g c,> <g c,> }
4357 Changes to the horizontal positions of the control points may be made
4358 in the same way, and two different curves starting at the same
4359 musical moment may also be shaped:
4361 @lilypond[verbatim,quote,ragged-right]
4363 c''8(\( a) a'4 e c\)
4364 \shape #'((0.7 . -0.4) (0.5 . -0.4) (0.3 . -0.3) (0 . -0.2)) Slur
4365 \shape #'((0 . 0) (0 . 0.5) (0 . 0.5) (0 . 0)) PhrasingSlur
4370 The @code{\shape} function can also displace the control points of
4371 curves which stretch across line breaks. Each piece of the broken
4372 curve can be given its own list of offsets. If changes to a
4373 particular segment are not needed, the empty list can serve as a
4374 placeholder. In this example the line break makes the single slur
4377 @lilypond[verbatim,quote,ragged-right]
4385 Changing the shapes of the two halves of the slur makes it clearer
4386 that the slur continues over the line break:
4388 @lilypond[verbatim,quote,ragged-right]
4389 % () may be used as a shorthand for ((0 . 0) (0 . 0) (0 . 0) (0 . 0))
4390 % if any of the segments does not need to be changed
4393 (( 0 . 0) (0 . 0) (0 . 0) (0 . 1))
4394 ((0.5 . 1.5) (1 . 0) (0 . 0) (0 . -1.5))
4402 If an S-shaped curve is required the control points must always be
4403 adjusted manually --- LilyPond will never select such shapes
4406 @lilypond[verbatim,quote]
4408 c8( e b-> f d' a e-> g)
4409 \shape #'((0 . -1) (5.5 . -0.5) (-5.5 . -10.5) (0 . -5.5)) PhrasingSlur
4410 c8\( e b-> f d' a e-> g\)
4414 @subsubsubheading Specifying control points explicitly
4416 The coordinates of the Bézier control points are specified in units
4417 of staff-spaces. The X@tie{}coordinate is relative to the reference
4418 point of the note to which the tie or slur is attached, and the
4419 Y@tie{}coordinate is relative to the staff center line. The
4420 coordinates are specified as a list of four pairs of decimal numbers
4421 (reals). One approach is to estimate the coordinates of the two
4422 end points, and then guess the two intermediate points. The optimum
4423 values are then found by trial and error. Be aware that these values
4424 may need to be manually adjusted if any further changes are made to
4425 the music or the layout.
4427 One situation where specifying the control points explicitly is
4428 preferable to specifying displacements is when they need to be
4429 specified relative to a single note. Here is an example of this.
4430 It shows one way of indicating a slur extending into alternative
4431 sections of a volta repeat.
4433 @lilypond[verbatim,quote]
4436 \repeat volta 3 { c4 d( e f }
4441 % create a slur and move it to a new position
4442 % the <> is just an empty chord to carry the slur termination
4443 -\tweak control-points #'((-2 . 3.8) (-1 . 3.9) (0 . 4) (1 . 3.4)) ( <> )
4448 % create a slur and move it to a new position
4449 -\tweak control-points #'((-2 . 3) (-1 . 3.1) (0 . 3.2) (1 . 2.4)) ( <> )
4457 It is not possible to modify shapes of ties or slurs by changing
4458 the @code{control-points} property if there are multiple ties or slurs
4459 at the same musical moment -- the @code{\tweak} command will also not
4460 work in this case. However, the @code{tie-configuration} property of
4461 @code{TieColumn} can be overridden to set start line and direction as
4465 Internals Reference:
4466 @rinternals{TieColumn}.
4469 @node Modifying broken spanners
4470 @subsection Modifying broken spanners
4473 * Using alterBroken::
4476 @node Using alterBroken
4477 @unnumberedsubsubsec Using @code{\alterBroken}
4479 @cindex spanners, modifying
4480 @cindex broken spanners, modifying
4481 @funindex \alterBroken
4483 When a spanner crosses a line break or breaks, each piece
4484 inherits the attributes of the original spanner. Thus, ordinary
4485 tweaking of a broken spanner applies the same modifications to
4486 each of its segments. In the example below, overriding
4487 @code{thickness} affects the slur on either side of the line
4490 @lilypond[verbatim,quote,ragged-right]
4493 \once\override Slur.thickness = 10
4500 Independently modifying the appearance of individual pieces
4501 of a broken spanner is possible with the @code{\alterBroken}
4502 command. This command can produce either an @code{\override}
4503 or a @code{\tweak} of a spanner property.
4505 The syntax for @code{\alterBroken} is
4508 [-]\alterBroken @var{property} @var{values} @var{item}
4511 The argument @var{values} is a list of values, one for each
4512 broken piece. If @var{item} is a grob name like @code{Slur} or
4513 @code{Staff.PianoPedalBracket}, the result is an @code{\override}
4514 of the specified grob type. If @var{item} is a music expression
4515 such as @qq{(} or @qq{[} the result is the same music expression
4516 with an appropriate tweak applied.
4518 The leading hyphen must be used with the @code{\tweak} form. Do
4519 not add it when @code{\alterBroken} is used as an
4522 In its @code{\override} usage, @code{\alterBroken} may be
4523 prefaced by @code{\once} or @code{\temporary} and reverted by
4524 using @code{\revert} with @var{property}.
4526 The following code applies an independent @code{\override} to
4527 each of the slur segments in the previous example:
4529 @lilypond[verbatim,quote,ragged-right]
4532 \alterBroken thickness #'(10 1) Slur
4539 The @code{\alterBroken} command may be used with any spanner
4540 object, including @code{Tie}, @code{PhrasingSlur}, @code{Beam}
4541 and @code{TextSpanner}. For example, an editor preparing a
4542 scholarly edition may wish to indicate the absence of part of a
4543 phrasing slur in a source by dashing only the segment which has
4544 been added. The following example illustrates how this can be
4545 done, in this case using the @code{\tweak} form of the command:
4547 @lilypond[verbatim,quote,ragged-right]
4548 % The empty list is conveniently used below, because it is the
4549 % default setting of dash-definition, resulting in a solid curve.
4551 c''2-\alterBroken dash-definition #'(() ((0 1.0 0.4 0.75))) \(e
4557 It is important to understand that @code{\alterBroken} will set
4558 each piece of a broken spanner to the corresponding value in
4559 @var{values}. When there are fewer values than pieces, any
4560 additional piece will be assigned the empty list. This may lead
4561 to undesired results if the layout property is not set to the
4562 empty list by default. In such cases, each segment should be
4563 assigned an appropriate value.
4566 Line breaks may occur in different places following changes in
4567 layout. Settings chosen for @code{\alterBroken} may be unsuitable
4568 for a spanner that is no longer broken or is split into more
4569 segments than before. Explicit use of @code{\break} can guard
4570 against this situation.
4572 The @code{\alterBroken} command is ineffective for spanner
4573 properties accessed before line-breaking such as
4578 @rextend{Difficult tweaks}.
4581 @node Unpure-pure containers
4582 @subsection Unpure-pure containers
4584 @cindex Scheme, pure containers
4585 @cindex Scheme, unpure containers
4586 @cindex pure containers, Scheme
4587 @cindex unpure containers, Scheme
4588 @cindex horizontal spacing, overriding
4590 Unpure-pure containers are useful for overriding @emph{Y-axis} spacing
4591 calculations - specifically @code{Y-offset} and @code{Y-extent} - with a
4592 Scheme function instead of a literal (i.e., a number or pair).
4594 For certain grobs, the @code{Y-extent} is based on the @code{stencil}
4595 property, overriding the stencil property of one of these will
4596 require an additional @code{Y-extent} override with an unpure-pure
4597 container. When a function overrides a @code{Y-offset} and/or
4598 @code{Y-extent} it is assumed that this will trigger line breaking
4599 calculations too early during compilation. So the function is not
4600 evaluated at all (usually returning a value of @samp{0} or
4601 @samp{'(0 . 0)}) which can result in collisions. A @q{pure} function
4602 will not affect properties, objects or grob suicides and therefore will
4603 always have its Y-axis-related evaluated correctly.
4605 Currently, there are about thirty functions that are already considered
4606 @q{pure} and Unpure-pure containers are a way to set functions not on
4607 this list as @q{pure}. The @q{pure} function is evaluated @emph{before}
4608 any line-breaking and so the horizontal spacing can be adjusted
4609 @q{in time}. The @q{unpure} function is then evaluated @emph{after}
4612 @warning{As it is difficult to always know which functions are on this
4613 list we recommend that any @q{pure} functions you create do not use
4614 @code{Beam} or @code{VerticalAlignment} grobs.}
4616 An unpure-pure container is constructed as follows;
4618 @code{(ly:make-unpure-pure-container f0 f1)}
4620 where @code{f0} is a function taking @var{n} arguments (@var{n >= 1})
4621 and the first argument must always be the grob. This is the function
4622 that gives the actual result. @var{f1} is the function being labeled
4623 as @q{pure} that takes @var{n + 2} arguments. Again, the first argument
4624 must always still be the grob but the second and third are @q{start}
4625 and @q{end} arguments.
4627 @var{start} and @var{end} are, for all intents and purposes, dummy
4628 values that only matter for @code{Spanners} (i.e @code{Hairpin} or
4629 @code{Beam}), that can return different height estimations based on a
4630 starting and ending column.
4632 The rest are the other arguments to the first function (which
4633 may be none if @var{n = 1}).
4635 The results of the second function are used as an approximation of the
4636 value needed which is then used by the first function to get the real
4637 value which is then used for fine-tuning much later during the spacing
4640 @c TODO: The following example supposedly showing a collision no longer
4641 @c 'works' since 2.18.x. Another example of a collision is needed.
4644 @lilypond[verbatim,quote,ragged-right]
4645 #(define (square-line-circle-space grob)
4646 (let* ((pitch (ly:event-property (ly:grob-property grob 'cause) 'pitch))
4647 (notename (ly:pitch-notename pitch)))
4648 (if (= 0 (modulo notename 2))
4649 (make-circle-stencil 0.5 0.0 #t)
4650 (make-filled-box-stencil '(0 . 1.0)
4653 squareLineCircleSpace = {
4654 \override NoteHead.stencil = #square-line-circle-space
4657 smartSquareLineCircleSpace = {
4658 \squareLineCircleSpace
4659 \override NoteHead.Y-extent =
4660 #(ly:make-unpure-pure-container
4661 ly:grob::stencil-height
4662 (lambda (grob start end) (ly:grob::stencil-height grob)))
4665 \new Voice \with { \remove "Stem_engraver" }
4667 \squareLineCircleSpace
4669 \smartSquareLineCircleSpace
4674 In the first measure, without the unpure-pure container, the spacing
4675 engine does not know the width of the note head and lets it collide with
4676 the accidentals. In the second measure, with unpure-pure containers,
4677 the spacing engine knows the width of the note heads and avoids the
4678 collision by lengthening the line accordingly.
4680 Usually for simple calculations nearly-identical functions for
4681 both the @q{unpure} and @q{pure} parts can be used, by only
4682 changing the number of arguments passed to, and the scope of, the
4683 function. This use case is frequent enough that
4684 @code{ly:make-unpure-pure-container} constructs such a second
4685 function by default when called with only one function argument.
4687 @warning{If a function is labeled as @q{pure} and it turns out not to
4688 be, the results can be unexpected.}
4691 @node Using music functions
4692 @section Using music functions
4694 @c TODO -- add @seealso, etc. to these subsections
4696 Where tweaks need to be reused with different music expressions,
4697 it is often convenient to make the tweak part of a @emph{music
4698 function}. In this section, we discuss only @emph{substitution}
4699 functions, where the object is to substitute a variable into a
4700 piece of LilyPond input code. Other more complex functions are
4701 described in @rextend{Music functions}.
4704 * Substitution function syntax::
4705 * Substitution function examples::
4708 @node Substitution function syntax
4709 @subsection Substitution function syntax
4711 Making a function that substitutes a variable into LilyPond
4712 code is easy. The general form of these functions is
4716 #(define-music-function
4717 (@var{arg1} @var{arg2} @dots{})
4718 (@var{type1?} @var{type2?} @dots{})
4720 @var{@dots{}music@dots{}}
4727 @multitable @columnfractions .33 .66
4728 @item @code{@var{argN}}
4729 @tab @var{n}th argument
4731 @item @code{@var{typeN?}}
4732 @tab a scheme @emph{type predicate} for which @code{@var{argN}}
4733 must return @code{#t}.
4735 @item @code{@var{@dots{}music@dots{}}}
4736 @tab normal LilyPond input, using @code{$} (in places where only
4737 LilyPond constructs are allowed) or @code{#} (to use it as a Scheme
4738 value or music function argument or music inside of music lists) to
4743 The list of type predicates is required. Some of the most common
4744 type predicates used in music functions are:
4748 cheap-list? @emph{(use instead of }@q{list?}@emph{ for faster processing)}
4760 For a list of available type predicates, see
4761 @ref{Predefined type predicates}. User-defined type predicates
4766 @ref{Predefined type predicates}.
4769 @rextend{Music functions}.
4772 @file{lily/music-scheme.cc},
4774 @file{scm/lily.scm}.
4777 @node Substitution function examples
4778 @subsection Substitution function examples
4780 This section introduces some substitution function examples.
4781 These are not intended to be exhaustive, but rather to demonstrate
4782 some of the possibilities of simple substitution functions.
4784 In the first example, a function is defined that simplifies
4785 setting the padding of a TextScript:
4787 @lilypond[quote,verbatim,ragged-right]
4789 #(define-music-function
4793 \once \override TextScript.padding = #padding
4797 c''4^"piu mosso" b a b
4799 c4^"piu mosso" b a b
4801 c4^"piu mosso" b a b
4805 In addition to numbers, we can use music expressions such
4806 as notes for arguments to music functions:
4808 @lilypond[quote,verbatim,ragged-right]
4810 #(define-music-function
4814 \tweak NoteHead.stencil #ly:text-interface::print
4815 \tweak NoteHead.text
4816 \markup \musicglyph #"custodes.mensural.u0"
4817 \tweak Stem.stencil ##f
4821 \relative { c'4 d e f \custosNote g }
4825 Both of those functions are simple single expressions where only
4826 the last element of a function call or override is missing. For
4827 those particular function definitions, there is a simpler
4828 alternative syntax, namely just writing out the constant part of
4829 the expression and replacing its final missing element with
4832 @lilypond[quote,verbatim,ragged-right]
4834 \once \override TextScript.padding = \etc
4837 c''4^"piu mosso" b a b
4839 c4^"piu mosso" b a b
4841 c4^"piu mosso" b a b
4845 @lilypond[quote,verbatim,ragged-right]
4847 \tweak NoteHead.stencil #ly:text-interface::print
4848 \tweak NoteHead.text
4849 \markup \musicglyph #"custodes.mensural.u0"
4850 \tweak Stem.stencil ##f
4853 \relative { c'4 d e f \custosNote g }
4857 Substitution functions with multiple arguments can be defined:
4859 @lilypond[quote,verbatim,ragged-right]
4861 #(define-music-function
4865 \once \override Score.MetronomeMark.padding = #padding
4866 \tempo \markup { \bold #tempotext }
4870 \tempo \markup { "Low tempo" }
4872 \tempoPadded #4.0 "High tempo"
4877 @c TODO: add appropriate @@ref's here.