1 @c -*- coding: utf-8; mode: texinfo; -*-
2 @node Changing defaults
3 @chapter Changing defaults
6 The purpose of LilyPond's design is to provide the finest output
7 quality as a default. Nevertheless, it may happen that you need to
8 change this default layout. The layout is controlled through a large
9 number of proverbial ``knobs and switches.'' This chapter does not
10 list each and every knob. Rather, it outlines what groups of controls
11 are available and explains how to lookup which knob to use for a
15 @cindex Program reference
17 The controls available for tuning are described in a separate
23 @ref{Top,Program reference,,lilypond-internals}.
26 lists all different variables, functions and options available in
27 LilyPond. It is written as a HTML document, which is available
28 @uref{http://@/lilypond@/.org/@/doc/@/v2.7/@/Documentation/@/user/@/lilypond@/-internals/,on@/-line},
29 but is also included with the LilyPond documentation package.
31 There are three areas where the default settings may be changed:
35 Output: changing the appearance of individual
36 objects. For example, changing stem directions or the location of
40 Context: changing aspects of the translation from music events to
41 notation. For example, giving each staff a separate time signature.
44 Global layout: changing the appearance of the spacing, line
45 breaks, and page dimensions.
48 Then there are separate systems for typesetting text (like
49 @emph{ritardando}) and selecting different fonts. This chapter also
52 Internally, LilyPond uses Scheme (a LISP dialect) to provide
53 infrastructure. Overriding layout decisions in effect accesses the
54 program internals, which requires Scheme input. Scheme elements are
55 introduced in a @code{.ly} file with the hash mark
56 @code{#}.@footnote{@ref{Scheme tutorial} contains a short tutorial
57 on entering numbers, lists, strings, and symbols in Scheme.}
61 * Interpretation contexts::
62 * The \override command::
66 @node Interpretation contexts
67 @section Interpretation contexts
69 When music is printed, a lot of notational elements must be added to the
70 input, which is often bare bones. For example, compare the input and
71 output of the following example:
73 @lilypond[quote,verbatim,relative=2,fragment]
77 The input is rather sparse, but in the output, bar lines, accidentals,
78 clef, and time signature are added. LilyPond @emph{interprets} the
79 input. During this step, the musical information is inspected in time
80 order, similar to reading a score from left to right. While reading,
81 the input, the program remembers where measure boundaries are, and what
82 pitches need explicit accidentals. This information can be presented on
83 several levels. For example, the effect of an accidental is limited
84 to a single staff, while a bar line must be synchronized across the
87 Within LilyPond, these rules and bits of information are grouped in
88 so-called Contexts. Examples of context are @context{Voice},
89 @context{Staff}, and @context{Score}. They are hierarchical, for
90 example, a @context{Staff} can contain many @context{Voice}s, and a
91 @context{Score} can contain many @context{Staff} contexts.
93 Each context has the responsibility for enforcing some notation rules,
94 creating some notation objects and maintaining the associated
95 properties. So, the synchronization of bar lines is handled at
96 @context{Score} context. The @context{Voice} may introduce an
97 accidental and then the @context{Staff} context maintains the rule to
98 show or suppress the accidental for the remainder of the measure.
100 For simple scores, contexts are created implicitly, and you need not
101 be aware of them. For larger pieces, such as piano music, they must be
102 created explicitly to make sure that you get as many staves as you
103 need, and that they are in the correct order. For typesetting pieces
104 with specialized notation, it can be useful to modify existing or
105 to define new contexts.
108 A complete description of all available contexts is in the program
111 @internalsref{Contexts}.
114 Translation @arrow{} Context.
117 @c [TODO: describe propagation]
121 * Creating contexts::
122 * Changing context properties on the fly::
123 * Modifying context plug-ins::
124 * Layout tunings within contexts::
125 * Changing context default settings::
126 * Defining new contexts::
129 @node Creating contexts
130 @subsection Creating contexts
132 For scores with only one voice and one staff, correct contexts are
133 created automatically. For more complex scores, it is necessary to
134 create them by hand. There are three commands that do this.
136 The easiest command is @code{\new}, and it also the quickest to type.
137 It is prepended to a music expression, for example
141 @cindex Context, creating
144 \new @var{type} @var{music expression}
148 where @var{type} is a context name (like @code{Staff} or
149 @code{Voice}). This command creates a new context, and starts
150 interpreting the @var{music expression} with that.
152 A practical application of @code{\new} is a score with many
153 staves. Each part that should be on its own staff, is preceded with
156 @lilypond[quote,verbatim,relative=2,ragged-right,fragment]
157 << \new Staff { c4 c }
162 The @code{\new} command may also give a name to the context,
165 \new @var{type} = @var{id} @var{music}
167 However, this user specified name is only used if there is no other
168 context already earlier with the same name.
170 @cindex @code{\context}
172 Like @code{\new}, the @code{\context} command also directs a music
173 expression to a context object, but gives the context an explicit name. The
177 \context @var{type} = @var{id} @var{music}
180 This form will search for an existing context of type @var{type}
181 called @var{id}. If that context does not exist yet, it is created.
182 This is useful if the context is referred to later on. For example, when
183 setting lyrics the melody is in a named context
186 \context Voice = "@b{tenor}" @var{music}
190 so the texts can be properly aligned to its notes,
193 \new Lyrics \lyricsto "@b{tenor}" @var{lyrics}
198 Another possibility is funneling two different music expressions into
199 one context. In the following example, articulations and notes are
204 arts = @{ s4-. s4-> @}
207 They are combined by sending both to the same @context{Voice} context,
210 << \new Staff \context Voice = "A" \music
211 \context Voice = "A" \arts
214 @lilypond[quote,ragged-right]
218 \new Staff \context Voice = "A" \music
219 \context Voice = "A" \arts
223 With this mechanism, it is possible to define an Urtext (original
224 edition), with the option to put several distinct articulations on the
227 @cindex creating contexts
229 The third command for creating contexts is
231 \context @var{type} @var{music}
236 This is similar to @code{\context} with @code{= @var{id}}, but matches
237 any context of type @var{type}, regardless of its given name.
239 This variant is used with music expressions that can be interpreted at
240 several levels. For example, the @code{\applyOutput} command (see
241 @ref{Running a function on all layout objects}). Without an explicit
242 @code{\context}, it is usually applied to @context{Voice}
245 \applyOutput #@var{function} % apply to Voice
248 To have it interpreted at the @context{Score} or @context{Staff} level use
252 \context Score \applyOutput #@var{function}
253 \context Staff \applyOutput #@var{function}
257 @node Changing context properties on the fly
258 @subsection Changing context properties on the fly
262 @cindex changing properties
264 Each context can have different @emph{properties}, variables contained
265 in that context. They can be changed during the interpretation step.
266 This is achieved by inserting the @code{\set} command in the music,
269 \set @var{context}.@var{prop} = #@var{value}
273 @lilypond[quote,verbatim,relative=2,fragment]
275 \set Score.skipBars = ##t
279 This command skips measures that have no notes. The result is that
280 multi-rests are condensed. The value assigned is a Scheme object. In
281 this case, it is @code{#t}, the boolean True value.
283 If the @var{context} argument is left out, then the current bottom-most
284 context (typically @context{ChordNames}, @context{Voice}, or
285 @context{Lyrics}) is used. In this example,
287 @lilypond[quote,verbatim,relative=2,fragment]
289 \set autoBeaming = ##f
294 the @var{context} argument to @code{\set} is left out, so automatic
295 beaming is switched off in the current @internalsref{Voice}. Note that
296 the bottom-most context does not always contain the property that you
297 wish to change -- for example, attempting to set the @code{skipBars}
298 property (of the bottom-most context, in this case @code{Voice}) will
301 @lilypond[quote,verbatim,relative=2,fragment]
307 Contexts are hierarchical, so if a bigger context was specified, for
308 example @context{Staff}, then the change would also apply to all
309 @context{Voice}s in the current stave. The change is applied
310 `on-the-fly', during the music, so that the setting only affects the
311 second group of eighth notes.
313 @cindex @code{\unset}
315 There is also an @code{\unset} command,
317 \unset @var{context}.@var{prop}
321 which removes the definition of @var{prop}. This command removes
322 the definition only if it is set in @var{context}, so
325 \set Staff.autoBeaming = ##f
329 introduces a property setting at @code{Staff} level. The setting also
330 applies to the current @code{Voice}. However,
333 \unset Voice.autoBeaming
337 does not have any effect. To cancel this setting, the @code{\unset}
338 must be specified on the same level as the original @code{\set}. In
339 other words, undoing the effect of @code{Staff.autoBeaming = ##f}
342 \unset Staff.autoBeaming
345 Like @code{\set}, the @var{context} argument does not have to be
346 specified for a bottom context, so the two statements
349 \set Voice.autoBeaming = ##t
350 \set autoBeaming = ##t
358 Settings that should only apply to a single time-step can be entered
359 with @code{\once}, for example in
361 @lilypond[quote,verbatim,relative=2,fragment]
363 \once \set fontSize = #4.7
368 the property @code{fontSize} is unset automatically after the second
371 A full description of all available context properties is in the
372 program reference, see
374 @internalsref{Tunable context properties}.
377 Translation @arrow{} Tunable context properties.
381 @node Modifying context plug-ins
382 @subsection Modifying context plug-ins
384 Notation contexts (like Score and Staff) not only store properties,
385 they also contain plug-ins, called ``engravers'' that create notation
386 elements. For example, the Voice context contains a
387 @code{Note_head_engraver} and the Staff context contains a
388 @code{Key_signature_engraver}.
390 For a full a description of each plug-in, see
392 @internalsref{Engravers}.
395 Program reference @arrow Translation @arrow{} Engravers.
397 Every context described in
399 @internalsref{Contexts}
402 Program reference @arrow Translation @arrow{} Context.
404 lists the engravers used for that context.
407 It can be useful to shuffle around these plug-ins. This is done by
408 starting a new context, with @code{\new} or @code{\context}, and
409 modifying it like this,
414 \new @var{context} \with @{
425 where the @dots{} should be the name of an engraver. Here is a simple
426 example which removes @code{Time_signature_engraver} and
427 @code{Clef_engraver} from a @code{Staff} context,
429 @lilypond[quote,relative=1,verbatim,fragment]
434 \remove "Time_signature_engraver"
435 \remove "Clef_engraver"
442 In the second staff there are no time signature or clef symbols. This
443 is a rather crude method of making objects disappear since it will affect
444 the entire staff. The spacing is adversely influenced too. A more
445 sophisticated method of blanking objects is shown in @ref{Common tweaks}.
447 The next example shows a practical application. Bar lines and time
448 signatures are normally synchronized across the score. This is done
449 by the @code{Timing_translator} and @code{Default_bar_line_engraver}.
450 This plug-in keeps an administration of time signature, location
451 within the measure, etc. By moving thes engraver from @code{Score} to
452 @code{Staff} context, we can have a score where each staff has its own
455 @cindex polymetric scores
456 @cindex Time signatures, multiple
458 @lilypond[quote,relative=1,ragged-right,verbatim,fragment]
460 \remove "Timing_translator"
461 \remove "Default_bar_line_engraver"
464 \consists "Timing_translator"
465 \consists "Default_bar_line_engraver"
471 \consists "Timing_translator"
472 \consists "Default_bar_line_engraver"
481 @node Layout tunings within contexts
482 @subsection Layout tunings within contexts
484 Each context is responsible for creating certain types of graphical
485 objects. The settings used for printing these objects are also stored by
486 context. By changing these settings, the appearance of objects can be
489 The syntax for this is
492 \override @var{context}.@var{name} #'@var{property} = #@var{value}
495 Here @var{name} is the name of a graphical object, like @code{Stem} or
496 @code{NoteHead}, and @var{property} is an internal variable of the
497 formatting system (`grob property' or `layout property'). The latter is a
498 symbol, so it must be quoted. The subsection @ref{Constructing a
499 tweak} explains what to fill in for @var{name}, @var{property}, and
500 @var{value}. Here we only discuss the functionality of this command.
505 \override Staff.Stem #'thickness = #4.0
509 makes stems thicker (the default is 1.3, with staff line thickness as a
510 unit). Since the command specifies @context{Staff} as context, it only
511 applies to the current staff. Other staves will keep their normal
512 appearance. Here we see the command in action:
514 @lilypond[quote,verbatim,relative=2,fragment]
516 \override Staff.Stem #'thickness = #4.0
522 The @code{\override} command changes the definition of the @code{Stem}
523 within the current @context{Staff}. After the command is interpreted
524 all stems are thickened.
526 Analogous to @code{\set}, the @var{context} argument may be left out,
527 causing it to default to @context{Voice}, and adding @code{\once} applies
528 the change during one timestep only
530 @lilypond[quote,fragment,verbatim,relative=2]
532 \once \override Stem #'thickness = #4.0
537 The @code{\override} must be done before the object is
538 started. Therefore, when altering @emph{Spanner} objects, like slurs or
539 beams, the @code{\override} command must be executed at the moment when
540 the object is created. In this example,
543 @lilypond[quote,fragment,verbatim,relative=2]
544 \override Slur #'thickness = #3.0
546 \override Beam #'thickness = #0.6
551 the slur is fatter but the beam is not. This is because the command for
552 @code{Beam} comes after the Beam is started. Therefore it has no effect.
554 Analogous to @code{\unset}, the @code{\revert} command for a context
555 undoes an @code{\override} command; like with @code{\unset}, it only
556 affects settings that were made in the same context. In other words, the
557 @code{\revert} in the next example does not do anything.
560 \override Voice.Stem #'thickness = #4.0
561 \revert Staff.Stem #'thickness
564 Some tweakable options are called ``subproperties'' and reside inside
565 properties. To tweak those, use
568 \override Stem #'details #'beamed-lengths = #'(4 4 3)
574 Internals: @internalsref{OverrideProperty}, @internalsref{RevertProperty},
575 @internalsref{PropertySet}, @internalsref{Backend}, and
576 @internalsref{All layout objects}.
581 The back-end is not very strict in type-checking object properties.
582 Cyclic references in Scheme values for properties can cause hangs
586 @node Changing context default settings
587 @subsection Changing context default settings
589 The adjustments of the previous subsections (@ref{Changing context
590 properties on the fly}, @ref{Modifying context plug-ins}, and
591 @ref{Layout tunings within contexts}) can also be entered separately
592 from the music, in the @code{\layout} block,
601 \override Stem #'thickness = #4.0
602 \remove "Time_signature_engraver"
613 takes the existing definition for context @context{Staff} from the
614 identifier @code{\Staff}.
619 \override Stem #'thickness = #4.0
620 \remove "Time_signature_engraver"
624 affect all staves in the score.
626 Other contexts can be modified analogously.
628 The @code{\set} keyword is optional within the @code{\layout} block, so
644 It is not possible to collect context changes in a variable, and apply
645 them to one @code{\context} definition by referring to that variable.
647 The @code{\RemoveEmptyStaffContext} will override your current
648 @code{\Staff} variable. If you wish to change the defaults for a
649 staff that uses @code{\RemoveEmptyStaffContext}, you must do so
650 after calling @code{\RemoveemptyStaffContext}, ie
655 \RemoveEmptyStaffContext
657 \override Stem #'thickness = #4.0
663 @node Defining new contexts
664 @subsection Defining new contexts
666 Specific contexts, like @context{Staff} and @code{Voice}, are made of
667 simple building blocks, and it is possible to compose engraver
668 plug-ins in different combinations, thereby creating new types of
671 The next example shows how to build a different type of
672 @context{Voice} context from scratch. It will be similar to
673 @code{Voice}, but prints centered slash noteheads only. It can be used
674 to indicate improvisation in Jazz pieces,
676 @lilypond[quote,ragged-right]
679 \type "Engraver_group"
680 \consists "Note_heads_engraver"
681 \consists "Text_engraver"
682 \consists Pitch_squash_engraver
683 squashedPosition = #0
684 \override NoteHead #'style = #'slash
685 \override Stem #'transparent = ##t
689 \accepts "ImproVoice"
693 a4 d8 bes8 \new ImproVoice { c4^"ad lib" c
694 c4 c^"undress" c_"while playing :)" c }
700 These settings are again done within a @code{\context} block inside a
701 @code{\layout} block,
711 In the following discussion, the example input shown should go on the
712 @dots{} in the previous fragment.
714 First, the context gets a name. Instead of @context{Voice} it
715 will be called @context{ImproVoice},
721 Since it is similar to the @context{Voice}, we want commands that work
722 on (existing) @context{Voice}s to remain working. This is achieved by
723 giving the new context an alias @context{Voice},
729 The context will print notes, and instructive texts
732 \consists Note_heads_engraver
733 \consists Text_engraver
736 but only on the center line,
739 \consists Pitch_squash_engraver
740 squashedPosition = #0
743 The @internalsref{Pitch_squash_engraver} modifies note heads (created
744 by @internalsref{Note_heads_engraver}) and sets their vertical
745 position to the value of @code{squashedPosition}, in this case@tie{}@code{0},
748 The notes look like a slash, without a stem,
751 \override NoteHead #'style = #'slash
752 \override Stem #'transparent = ##t
756 All these plug-ins have to cooperate, and this is achieved with a
757 special plug-in, which must be marked with the keyword @code{\type}.
758 This should always be @internalsref{Engraver_group},
761 \type "Engraver_group"
769 \type "Engraver_group"
770 \consists "Note_heads_engraver"
771 \consists "Text_engraver"
772 \consists Pitch_squash_engraver
773 squashedPosition = #0
774 \override NoteHead #'style = #'slash
775 \override Stem #'transparent = ##t
780 Contexts form hierarchies. We want to hang the @context{ImproVoice}
781 under @context{Staff}, just like normal @code{Voice}s. Therefore, we
782 modify the @code{Staff} definition with the @code{\accepts}
783 command,@footnote{The opposite of @code{\accepts} is @code{\denies},
784 which is sometimes needed when reusing existing context definitions.}
795 Putting both into a @code{\layout} block, like
805 \accepts "ImproVoice"
810 Then the output at the start of this subsection can be entered as
818 c c_"while playing :)"
827 @node The \override command
828 @section The \override command
830 In the previous section, we have already touched on a command that
831 changes layout details: the @code{\override} command. In this section,
832 we will look in more detail at how to use the command in practice.
833 First, we will give a few versatile commands that are sufficient
834 for many situations. The next section will discuss the general use of
839 * Constructing a tweak::
840 * Navigating the program reference::
841 * Layout interfaces::
842 * Determining the grob property::
843 * Objects connected to the input::
849 @node Constructing a tweak
850 @subsection Constructing a tweak
852 The general procedure of changing output, that is, entering
856 \override Voice.Stem #'thickness = #3.0
860 means that we have to determine these bits of information:
863 @item the context: here @context{Voice}.
864 @item the layout object: here @code{Stem}.
865 @item the layout property: here @code{thickness}
866 @item a sensible value: here @code{3.0}
870 @cindex internal documentation
871 @cindex finding graphical objects
872 @cindex graphical object descriptions
874 @cindex @code{\override}
875 @cindex internal documentation
877 We demonstrate how to glean this information from the notation manual
878 and the program reference.
880 @node Navigating the program reference
881 @subsection Navigating the program reference
883 Suppose we want to move the fingering indication in the fragment
886 @lilypond[quote,fragment,relative=2,verbatim]
892 If you visit the documentation on fingering instructions (in
893 @ref{Fingering instructions}), you will notice that there is written:
898 Program reference: @internalsref{FingerEvent} and @internalsref{Fingering}.
904 This fragment points to two parts of the program reference: a page
905 on @code{FingerEvent} and one on @code{Fingering}.
907 The page on @code{FingerEvent} describes the properties of the music
908 expression for the input @code{-2}. The page contains many links
909 forward. For example, it says
912 Accepted by: @internalsref{Fingering_engraver},
916 That link brings us to the documentation for the Engraver, the
920 This engraver creates the following layout objects: @internalsref{Fingering}.
923 In other words, once the @code{FingerEvent}s are interpreted, the
924 @code{Fingering_engraver} plug-in will process them.
927 @c I can't figure out what this is supposed to mean. -gp
929 The @code{Fingering_engraver} is also listed to create
930 @internalsref{Fingering} objects,
932 @c old info? it doesn't make any sense to me with our current docs.
934 second bit of information listed under @b{See also} in the Notation
938 By clicking around in the program reference, we can follow the
939 flow of information within the program, either forward (like we did
940 here), or backwards, following links like this:
944 @item @internalsref{Fingering}:
945 @internalsref{Fingering} objects are created by:
946 @b{@internalsref{Fingering_engraver}}
948 @item @internalsref{Fingering_engraver}:
949 Music types accepted: @b{@internalsref{fingering-event}}
951 @item @internalsref{fingering-event}:
952 Music event type @code{fingering-event} is in Music expressions named
953 @b{@internalsref{FingerEvent}}
956 This path goes against the flow of information in the program: it
957 starts from the output, and ends at the input event.
959 The program reference can also be browsed like a normal document. It
960 contains a chapter on
962 @internalsref{Music definitions},
965 @code{Music definitions}
967 on @internalsref{Translation}, and the @internalsref{Backend}. Every
968 chapter lists all the definitions used, and all properties that may be
972 @node Layout interfaces
973 @subsection Layout interfaces
975 @cindex interface, layout
976 @cindex layout interface
979 The HTML page that we found in the previous section, describes the
980 layout object called @internalsref{Fingering}. Such an object is a
981 symbol within the score. It has properties that store numbers (like
982 thicknesses and directions), but also pointers to related objects. A
983 layout object is also called a @emph{Grob}, which is short for Graphical
984 Object. For more details about Grobs, see @internalsref{grob-interface}.
986 The page for @code{Fingering} lists the definitions for the
987 @code{Fingering} object. For example, the page says
990 @code{padding} (dimension, in staff space):
996 which means that the number will be kept at a distance of at least 0.6
1000 Each layout object may have several functions as a notational or
1001 typographical element. For example, the Fingering object
1002 has the following aspects
1006 Its size is independent of the horizontal spacing, unlike slurs or beams.
1009 It is a piece of text. Granted, it is usually a very short text.
1012 That piece of text is typeset with a font, unlike slurs or beams.
1015 Horizontally, the center of the symbol should be aligned to the
1016 center of the notehead.
1019 Vertically, the symbol is placed next to the note and the staff.
1022 The vertical position is also coordinated with other super- and subscript
1026 Each of these aspects is captured in so-called @emph{interface}s,
1027 which are listed on the @internalsref{Fingering} page at the bottom
1030 This object supports the following interfaces:
1031 @internalsref{item-interface},
1032 @internalsref{self-alignment-interface},
1033 @internalsref{side-position-interface}, @internalsref{text-interface},
1034 @internalsref{text-script-interface}, @internalsref{font-interface},
1035 @internalsref{finger-interface}, and @internalsref{grob-interface}.
1038 Clicking any of the links will take you to the page of the respective
1039 object interface. Each interface has a number of properties. Some of
1040 them are not user-serviceable (``Internal properties''), but others
1043 We have been talking of @emph{the} @code{Fingering} object, but actually it
1044 does not amount to much. The initialization file
1045 @file{scm/@/define@/-grobs@/.scm} shows the soul of the `object',
1050 (avoid-slur . around)
1051 (slur-padding . 0.2)
1052 (staff-padding . 0.5)
1053 (self-alignment-X . 0)
1054 (self-alignment-Y . 0)
1055 (script-priority . 100)
1056 (stencil . ,ly:text-interface::print)
1057 (direction . ,ly:script-interface::calc-direction)
1058 (font-encoding . fetaNumber)
1059 (font-size . -5) ; don't overlap when next to heads.
1060 (meta . ((class . Item)
1061 (interfaces . (finger-interface
1063 text-script-interface
1065 side-position-interface
1066 self-alignment-interface
1067 item-interface))))))
1071 As you can see, the @code{Fingering} object is nothing more than a
1072 bunch of variable settings, and the webpage in the Program Reference
1073 is directly generated from this definition.
1075 @node Determining the grob property
1076 @subsection Determining the grob property
1079 Recall that we wanted to change the position of the @b{2} in
1081 @lilypond[quote,fragment,relative=2,verbatim]
1087 Since the @b{2} is vertically positioned next to its note, we have to
1088 meddle with the interface associated with this positioning. This is
1089 done using @code{side-position-interface}. The page for this interface
1093 @code{side-position-interface}
1095 Position a victim object (this one) next to other objects (the
1096 support). The property @code{direction} signifies where to put the
1097 victim object relative to the support (left or right, up or down?)
1102 below this description, the variable @code{padding} is described as
1107 (dimension, in staff space)
1109 Add this much extra space between objects that are next to each other.
1113 By increasing the value of @code{padding}, we can move away the
1114 fingering. The following command inserts 3 staff spaces of white
1115 between the note and the fingering:
1117 \once \override Voice.Fingering #'padding = #3
1120 Inserting this command before the Fingering object is created,
1121 i.e., before @code{c2}, yields the following result:
1123 @lilypond[quote,relative=2,fragment,verbatim]
1124 \once \override Voice.Fingering #'padding = #3
1131 In this case, the context for this tweak is @context{Voice}. This
1132 fact can also be deduced from the program reference, for the page for
1133 the @internalsref{Fingering_engraver} plug-in says
1136 Fingering_engraver is part of contexts: @dots{} @b{@internalsref{Voice}}
1139 @node Objects connected to the input
1140 @subsection Objects connected to the input
1142 In some cases, it is possible to take a short-cut for tuning graphical
1143 objects. For objects that result directly from a piece of the input,
1144 you can use the @code{\tweak} function, for example
1146 @lilypond[relative=2,fragment,verbatim,ragged-right]
1149 \tweak #'color #red d
1151 \tweak #'duration-log #1 a
1152 >4-\tweak #'padding #10 -.
1155 As you can see, properties are set directly in the objects directly,
1156 without mentioning the grob name or context where this should be
1159 This technique only works for objects that are directly connected to
1160 an @internalsref{event} from the input, for example
1163 @item note heads, caused by chord-pitch.
1164 @item articulation signs, caused by articulation instructions
1167 It notably does not work for stems and accidentals (these are caused
1168 by note heads, not by music events) or clefs (these are not caused by
1169 music inputs, but rather by the change of a property value).
1172 @node Difficult tweaks
1173 @subsection Difficult tweaks
1175 There are a few classes of difficult adjustments.
1181 One type of difficult adjustment is the appearance of spanner objects,
1182 such as slur and tie. Initially, only one of these objects is created,
1183 and they can be adjusted with the normal mechanism. However, in some
1184 cases the spanners cross line breaks. If this happens, these objects
1185 are cloned. A separate object is created for every system that it is
1186 in. These are clones of the original object and inherit all
1187 properties, including @code{\override}s.
1190 In other words, an @code{\override} always affects all pieces of a
1191 broken spanner. To change only one part of a spanner at a line break,
1192 it is necessary to hook into the formatting process. The
1193 @code{after-line-breaking} callback contains the Scheme procedure that
1194 is called after the line breaks have been determined, and layout
1195 objects have been split over different systems.
1197 In the following example, we define a procedure
1198 @code{my-callback}. This procedure
1202 determines if we have been split across line breaks
1204 if yes, retrieves all the split objects
1206 checks if we are the last of the split objects
1208 if yes, it sets @code{extra-offset}.
1211 This procedure is installed into @internalsref{Tie}, so the last part
1212 of the broken tie is translated up.
1214 @lilypond[quote,verbatim,ragged-right]
1215 #(define (my-callback grob)
1217 ; have we been split?
1218 (orig (ly:grob-original grob))
1220 ; if yes, get the split pieces (our siblings)
1221 (siblings (if (ly:grob? orig)
1222 (ly:spanner-broken-into orig) '() )))
1224 (if (and (>= (length siblings) 2)
1225 (eq? (car (last-pair siblings)) grob))
1226 (ly:grob-set-property! grob 'extra-offset '(-2 . 5)))))
1229 \override Tie #'after-line-breaking =
1236 When applying this trick, the new @code{after-line-breaking} callback
1237 should also call the old one @code{after-line-breaking}, if there is
1238 one. For example, if using this with @code{Hairpin},
1239 @code{ly:hairpin::after-line-breaking} should also be called.
1242 @item Some objects cannot be changed with @code{\override} for
1243 technical reasons. Examples of those are @code{NonMusicalPaperColumn}
1244 and @code{PaperColumn}. They can be changed with the
1245 @code{\outputProperty} function, which works similar to @code{\once
1246 \override}, but uses a different syntax,
1250 #"Score.NonMusicalPaperColumn" % Grob name
1251 #'line-break-system-details % Property name
1252 #'((next-padding . 20)) % Value