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}
168 @cindex @code{\context}
170 Like @code{\new}, the @code{\context} command also directs a music
171 expression to a context object, but gives the context an extra name. The
175 \context @var{type} = @var{id} @var{music}
178 This form will search for an existing context of type @var{type}
179 called @var{id}. If that context does not exist yet, it is created.
180 This is useful if the context is referred to later on. For example, when
181 setting lyrics the melody is in a named context
184 \context Voice = "@b{tenor}" @var{music}
188 so the texts can be properly aligned to its notes,
191 \new Lyrics \lyricsto "@b{tenor}" @var{lyrics}
196 Another possibility is funneling two different music expressions into
197 one context. In the following example, articulations and notes are
202 arts = @{ s4-. s4-> @}
205 They are combined by sending both to the same @context{Voice} context,
208 << \new Staff \context Voice = "A" \music
209 \context Voice = "A" \arts
212 @lilypond[quote,ragged-right]
216 \new Staff \context Voice = "A" \music
217 \context Voice = "A" \arts
221 With this mechanism, it is possible to define an Urtext (original
222 edition), with the option to put several distinct articulations on the
225 @cindex creating contexts
227 The third command for creating contexts is
229 \context @var{type} @var{music}
234 This is similar to @code{\context} with @code{= @var{id}}, but matches
235 any context of type @var{type}, regardless of its given name.
237 This variant is used with music expressions that can be interpreted at
238 several levels. For example, the @code{\applyOutput} command (see
239 @ref{Running a function on all layout objects}). Without an explicit
240 @code{\context}, it is usually applied to @context{Voice}
243 \applyOutput #@var{function} % apply to Voice
246 To have it interpreted at the @context{Score} or @context{Staff} level use
250 \context Score \applyOutput #@var{function}
251 \context Staff \applyOutput #@var{function}
255 @node Changing context properties on the fly
256 @subsection Changing context properties on the fly
260 @cindex changing properties
262 Each context can have different @emph{properties}, variables contained
263 in that context. They can be changed during the interpretation step.
264 This is achieved by inserting the @code{\set} command in the music,
267 \set @var{context}.@var{prop} = #@var{value}
271 @lilypond[quote,verbatim,relative=2,fragment]
273 \set Score.skipBars = ##t
277 This command skips measures that have no notes. The result is that
278 multi-rests are condensed. The value assigned is a Scheme object. In
279 this case, it is @code{#t}, the boolean True value.
281 If the @var{context} argument is left out, then the current bottom-most
282 context (typically @context{ChordNames}, @context{Voice}, or
283 @context{Lyrics}) is used. In this example,
285 @lilypond[quote,verbatim,relative=2,fragment]
287 \set autoBeaming = ##f
292 the @var{context} argument to @code{\set} is left out, so automatic
293 beaming is switched off in the current @internalsref{Voice}. Note that
294 the bottom-most context does not always contain the property that you
295 wish to change -- for example, attempting to set the @code{skipBars}
296 property (of the bottom-most context, in this case @code{Voice}) will
299 @lilypond[quote,verbatim,relative=2,fragment]
305 Contexts are hierarchical, so if a bigger context was specified, for
306 example @context{Staff}, then the change would also apply to all
307 @context{Voice}s in the current stave. The change is applied
308 `on-the-fly', during the music, so that the setting only affects the
309 second group of eighth notes.
311 @cindex @code{\unset}
313 There is also an @code{\unset} command,
315 \unset @var{context}.@var{prop}
319 which removes the definition of @var{prop}. This command removes
320 the definition only if it is set in @var{context}, so
323 \set Staff.autoBeaming = ##f
327 introduces a property setting at @code{Staff} level. The setting also
328 applies to the current @code{Voice}. However,
331 \unset Voice.autoBeaming
335 does not have any effect. To cancel this setting, the @code{\unset}
336 must be specified on the same level as the original @code{\set}. In
337 other words, undoing the effect of @code{Staff.autoBeaming = ##f}
340 \unset Staff.autoBeaming
343 Like @code{\set}, the @var{context} argument does not have to be
344 specified for a bottom context, so the two statements
347 \set Voice.autoBeaming = ##t
348 \set autoBeaming = ##t
356 Settings that should only apply to a single time-step can be entered
357 with @code{\once}, for example in
359 @lilypond[quote,verbatim,relative=2,fragment]
361 \once \set fontSize = #4.7
366 the property @code{fontSize} is unset automatically after the second
369 A full description of all available context properties is in the
370 program reference, see
372 @internalsref{Tunable context properties}.
375 Translation @arrow{} Tunable context properties.
379 @node Modifying context plug-ins
380 @subsection Modifying context plug-ins
382 Notation contexts (like Score and Staff) not only store properties,
383 they also contain plug-ins, called ``engravers'' that create notation
384 elements. For example, the Voice context contains a
385 @code{Note_head_engraver} and the Staff context contains a
386 @code{Key_signature_engraver}.
388 For a full a description of each plug-in, see
390 @internalsref{Engravers}.
393 Program reference @arrow Translation @arrow{} Engravers.
395 Every context described in
397 @internalsref{Contexts}
400 Program reference @arrow Translation @arrow{} Context.
402 lists the engravers used for that context.
405 It can be useful to shuffle around these plug-ins. This is done by
406 starting a new context, with @code{\new} or @code{\context}, and
407 modifying it like this,
412 \new @var{context} \with @{
423 where the @dots{} should be the name of an engraver. Here is a simple
424 example which removes @code{Time_signature_engraver} and
425 @code{Clef_engraver} from a @code{Staff} context,
427 @lilypond[quote,relative=1,verbatim,fragment]
432 \remove "Time_signature_engraver"
433 \remove "Clef_engraver"
440 In the second staff there are no time signature or clef symbols. This
441 is a rather crude method of making objects disappear since it will affect
442 the entire staff. The spacing is adversely influenced too. A more
443 sophisticated method of blanking objects is shown in @ref{Common tweaks}.
445 The next example shows a practical application. Bar lines and time
446 signatures are normally synchronized across the score. This is done
447 by the @code{Timing_translator} and @code{Default_bar_line_engraver}.
448 This plug-in keeps an administration of time signature, location
449 within the measure, etc. By moving thes engraver from @code{Score} to
450 @code{Staff} context, we can have a score where each staff has its own
453 @cindex polymetric scores
454 @cindex Time signatures, multiple
456 @lilypond[quote,relative=1,ragged-right,verbatim,fragment]
458 \remove "Timing_translator"
459 \remove "Default_bar_line_engraver"
462 \consists "Timing_translator"
463 \consists "Default_bar_line_engraver"
469 \consists "Timing_translator"
470 \consists "Default_bar_line_engraver"
479 @node Layout tunings within contexts
480 @subsection Layout tunings within contexts
482 Each context is responsible for creating certain types of graphical
483 objects. The settings used for printing these objects are also stored by
484 context. By changing these settings, the appearance of objects can be
487 The syntax for this is
490 \override @var{context}.@var{name} #'@var{property} = #@var{value}
493 Here @var{name} is the name of a graphical object, like @code{Stem} or
494 @code{NoteHead}, and @var{property} is an internal variable of the
495 formatting system (`grob property' or `layout property'). The latter is a
496 symbol, so it must be quoted. The subsection @ref{Constructing a
497 tweak} explains what to fill in for @var{name}, @var{property}, and
498 @var{value}. Here we only discuss the functionality of this command.
503 \override Staff.Stem #'thickness = #4.0
507 makes stems thicker (the default is 1.3, with staff line thickness as a
508 unit). Since the command specifies @context{Staff} as context, it only
509 applies to the current staff. Other staves will keep their normal
510 appearance. Here we see the command in action:
512 @lilypond[quote,verbatim,relative=2,fragment]
514 \override Staff.Stem #'thickness = #4.0
520 The @code{\override} command changes the definition of the @code{Stem}
521 within the current @context{Staff}. After the command is interpreted
522 all stems are thickened.
524 Analogous to @code{\set}, the @var{context} argument may be left out,
525 causing it to default to @context{Voice}, and adding @code{\once} applies
526 the change during one timestep only
528 @lilypond[quote,fragment,verbatim,relative=2]
530 \once \override Stem #'thickness = #4.0
535 The @code{\override} must be done before the object is
536 started. Therefore, when altering @emph{Spanner} objects, like slurs or
537 beams, the @code{\override} command must be executed at the moment when
538 the object is created. In this example,
541 @lilypond[quote,fragment,verbatim,relative=2]
542 \override Slur #'thickness = #3.0
544 \override Beam #'thickness = #0.6
549 the slur is fatter but the beam is not. This is because the command for
550 @code{Beam} comes after the Beam is started. Therefore it has no effect.
552 Analogous to @code{\unset}, the @code{\revert} command for a context
553 undoes an @code{\override} command; like with @code{\unset}, it only
554 affects settings that were made in the same context. In other words, the
555 @code{\revert} in the next example does not do anything.
558 \override Voice.Stem #'thickness = #4.0
559 \revert Staff.Stem #'thickness
562 Some tweakable options are called ``subproperties'' and reside inside
563 properties. To tweak those, use
566 \override Stem #'details #'beamed-lengths = #'(4 4 3)
572 Internals: @internalsref{OverrideProperty}, @internalsref{RevertProperty},
573 @internalsref{PropertySet}, @internalsref{Backend}, and
574 @internalsref{All layout objects}.
579 The back-end is not very strict in type-checking object properties.
580 Cyclic references in Scheme values for properties can cause hangs
584 @node Changing context default settings
585 @subsection Changing context default settings
587 The adjustments of the previous subsections (@ref{Changing context
588 properties on the fly}, @ref{Modifying context plug-ins}, and
589 @ref{Layout tunings within contexts}) can also be entered separately
590 from the music, in the @code{\layout} block,
599 \override Stem #'thickness = #4.0
600 \remove "Time_signature_engraver"
611 takes the existing definition for context @context{Staff} from the
612 identifier @code{\Staff}.
617 \override Stem #'thickness = #4.0
618 \remove "Time_signature_engraver"
622 affect all staves in the score.
624 Other contexts can be modified analogously.
626 The @code{\set} keyword is optional within the @code{\layout} block, so
642 It is not possible to collect context changes in a variable, and apply
643 them to one @code{\context} definition by referring to that variable.
645 The @code{\RemoveEmptyStaffContext} will override your current
646 @code{\Staff} variable. If you wish to change the defaults for a
647 staff that uses @code{\RemoveEmptyStaffContext}, you must do so
648 after calling @code{\RemoveemptyStaffContext}, ie
653 \RemoveEmptyStaffContext
655 \override Stem #'thickness = #4.0
661 @node Defining new contexts
662 @subsection Defining new contexts
664 Specific contexts, like @context{Staff} and @code{Voice}, are made of
665 simple building blocks, and it is possible to compose engraver
666 plug-ins in different combinations, thereby creating new types of
669 The next example shows how to build a different type of
670 @context{Voice} context from scratch. It will be similar to
671 @code{Voice}, but prints centered slash noteheads only. It can be used
672 to indicate improvisation in Jazz pieces,
674 @lilypond[quote,ragged-right]
677 \type "Engraver_group"
678 \consists "Note_heads_engraver"
679 \consists "Text_engraver"
680 \consists Pitch_squash_engraver
681 squashedPosition = #0
682 \override NoteHead #'style = #'slash
683 \override Stem #'transparent = ##t
687 \accepts "ImproVoice"
691 a4 d8 bes8 \new ImproVoice { c4^"ad lib" c
692 c4 c^"undress" c_"while playing :)" c }
698 These settings are again done within a @code{\context} block inside a
699 @code{\layout} block,
709 In the following discussion, the example input shown should go on the
710 @dots{} in the previous fragment.
712 First, the context gets a name. Instead of @context{Voice} it
713 will be called @context{ImproVoice},
719 Since it is similar to the @context{Voice}, we want commands that work
720 on (existing) @context{Voice}s to remain working. This is achieved by
721 giving the new context an alias @context{Voice},
727 The context will print notes, and instructive texts
730 \consists Note_heads_engraver
731 \consists Text_engraver
734 but only on the center line,
737 \consists Pitch_squash_engraver
738 squashedPosition = #0
741 The @internalsref{Pitch_squash_engraver} modifies note heads (created
742 by @internalsref{Note_heads_engraver}) and sets their vertical
743 position to the value of @code{squashedPosition}, in this case@tie{}@code{0},
746 The notes look like a slash, without a stem,
749 \override NoteHead #'style = #'slash
750 \override Stem #'transparent = ##t
754 All these plug-ins have to cooperate, and this is achieved with a
755 special plug-in, which must be marked with the keyword @code{\type}.
756 This should always be @internalsref{Engraver_group},
759 \type "Engraver_group"
767 \type "Engraver_group"
768 \consists "Note_heads_engraver"
769 \consists "Text_engraver"
770 \consists Pitch_squash_engraver
771 squashedPosition = #0
772 \override NoteHead #'style = #'slash
773 \override Stem #'transparent = ##t
778 Contexts form hierarchies. We want to hang the @context{ImproVoice}
779 under @context{Staff}, just like normal @code{Voice}s. Therefore, we
780 modify the @code{Staff} definition with the @code{\accepts}
781 command,@footnote{The opposite of @code{\accepts} is @code{\denies},
782 which is sometimes needed when reusing existing context definitions.}
793 Putting both into a @code{\layout} block, like
803 \accepts "ImproVoice"
808 Then the output at the start of this subsection can be entered as
816 c c_"while playing :)"
825 @node The \override command
826 @section The \override command
828 In the previous section, we have already touched on a command that
829 changes layout details: the @code{\override} command. In this section,
830 we will look in more detail at how to use the command in practice.
831 First, we will give a few versatile commands that are sufficient
832 for many situations. The next section will discuss the general use of
837 * Constructing a tweak::
838 * Navigating the program reference::
839 * Layout interfaces::
840 * Determining the grob property::
841 * Objects connected to the input::
847 @node Constructing a tweak
848 @subsection Constructing a tweak
850 The general procedure of changing output, that is, entering
854 \override Voice.Stem #'thickness = #3.0
858 means that we have to determine these bits of information:
861 @item the context: here @context{Voice}.
862 @item the layout object: here @code{Stem}.
863 @item the layout property: here @code{thickness}
864 @item a sensible value: here @code{3.0}
868 @cindex internal documentation
869 @cindex finding graphical objects
870 @cindex graphical object descriptions
872 @cindex @code{\override}
873 @cindex internal documentation
875 We demonstrate how to glean this information from the notation manual
876 and the program reference.
878 @node Navigating the program reference
879 @subsection Navigating the program reference
881 Suppose we want to move the fingering indication in the fragment
884 @lilypond[quote,fragment,relative=2,verbatim]
890 If you visit the documentation on fingering instructions (in
891 @ref{Fingering instructions}), you will notice that there is written:
896 Program reference: @internalsref{FingerEvent} and @internalsref{Fingering}.
902 This fragment points to two parts of the program reference: a page
903 on @code{FingerEvent} and one on @code{Fingering}.
905 The page on @code{FingerEvent} describes the properties of the music
906 expression for the input @code{-2}. The page contains many links
907 forward. For example, it says
910 Accepted by: @internalsref{Fingering_engraver},
914 That link brings us to the documentation for the Engraver, the
918 This engraver creates the following layout objects: @internalsref{Fingering}.
921 In other words, once the @code{FingerEvent}s are interpreted, the
922 @code{Fingering_engraver} plug-in will process them.
925 @c I can't figure out what this is supposed to mean. -gp
927 The @code{Fingering_engraver} is also listed to create
928 @internalsref{Fingering} objects,
930 @c old info? it doesn't make any sense to me with our current docs.
932 second bit of information listed under @b{See also} in the Notation
936 By clicking around in the program reference, we can follow the
937 flow of information within the program, either forward (like we did
938 here), or backwards, following links like this:
942 @item @internalsref{Fingering}:
943 @internalsref{Fingering} objects are created by:
944 @b{@internalsref{Fingering_engraver}}
946 @item @internalsref{Fingering_engraver}:
947 Music types accepted: @b{@internalsref{fingering-event}}
949 @item @internalsref{fingering-event}:
950 Music event type @code{fingering-event} is in Music expressions named
951 @b{@internalsref{FingerEvent}}
954 This path goes against the flow of information in the program: it
955 starts from the output, and ends at the input event.
957 The program reference can also be browsed like a normal document. It
958 contains a chapter on
960 @internalsref{Music definitions},
963 @code{Music definitions}
965 on @internalsref{Translation}, and the @internalsref{Backend}. Every
966 chapter lists all the definitions used, and all properties that may be
970 @node Layout interfaces
971 @subsection Layout interfaces
973 @cindex interface, layout
974 @cindex layout interface
977 The HTML page that we found in the previous section, describes the
978 layout object called @internalsref{Fingering}. Such an object is a
979 symbol within the score. It has properties that store numbers (like
980 thicknesses and directions), but also pointers to related objects. A
981 layout object is also called a @emph{Grob}, which is short for Graphical
982 Object. For more details about Grobs, see @internalsref{grob-interface}.
984 The page for @code{Fingering} lists the definitions for the
985 @code{Fingering} object. For example, the page says
988 @code{padding} (dimension, in staff space):
994 which means that the number will be kept at a distance of at least 0.6
998 Each layout object may have several functions as a notational or
999 typographical element. For example, the Fingering object
1000 has the following aspects
1004 Its size is independent of the horizontal spacing, unlike slurs or beams.
1007 It is a piece of text. Granted, it is usually a very short text.
1010 That piece of text is typeset with a font, unlike slurs or beams.
1013 Horizontally, the center of the symbol should be aligned to the
1014 center of the notehead.
1017 Vertically, the symbol is placed next to the note and the staff.
1020 The vertical position is also coordinated with other super- and subscript
1024 Each of these aspects is captured in so-called @emph{interface}s,
1025 which are listed on the @internalsref{Fingering} page at the bottom
1028 This object supports the following interfaces:
1029 @internalsref{item-interface},
1030 @internalsref{self-alignment-interface},
1031 @internalsref{side-position-interface}, @internalsref{text-interface},
1032 @internalsref{text-script-interface}, @internalsref{font-interface},
1033 @internalsref{finger-interface}, and @internalsref{grob-interface}.
1036 Clicking any of the links will take you to the page of the respective
1037 object interface. Each interface has a number of properties. Some of
1038 them are not user-serviceable (``Internal properties''), but others
1041 We have been talking of @emph{the} @code{Fingering} object, but actually it
1042 does not amount to much. The initialization file
1043 @file{scm/@/define@/-grobs@/.scm} shows the soul of the `object',
1048 (avoid-slur . around)
1049 (slur-padding . 0.2)
1050 (staff-padding . 0.5)
1051 (self-alignment-X . 0)
1052 (self-alignment-Y . 0)
1053 (script-priority . 100)
1054 (stencil . ,ly:text-interface::print)
1055 (direction . ,ly:script-interface::calc-direction)
1056 (font-encoding . fetaNumber)
1057 (font-size . -5) ; don't overlap when next to heads.
1058 (meta . ((class . Item)
1059 (interfaces . (finger-interface
1061 text-script-interface
1063 side-position-interface
1064 self-alignment-interface
1065 item-interface))))))
1069 As you can see, the @code{Fingering} object is nothing more than a
1070 bunch of variable settings, and the webpage in the Program Reference
1071 is directly generated from this definition.
1073 @node Determining the grob property
1074 @subsection Determining the grob property
1077 Recall that we wanted to change the position of the @b{2} in
1079 @lilypond[quote,fragment,relative=2,verbatim]
1085 Since the @b{2} is vertically positioned next to its note, we have to
1086 meddle with the interface associated with this positioning. This is
1087 done using @code{side-position-interface}. The page for this interface
1091 @code{side-position-interface}
1093 Position a victim object (this one) next to other objects (the
1094 support). The property @code{direction} signifies where to put the
1095 victim object relative to the support (left or right, up or down?)
1100 below this description, the variable @code{padding} is described as
1105 (dimension, in staff space)
1107 Add this much extra space between objects that are next to each other.
1111 By increasing the value of @code{padding}, we can move away the
1112 fingering. The following command inserts 3 staff spaces of white
1113 between the note and the fingering:
1115 \once \override Voice.Fingering #'padding = #3
1118 Inserting this command before the Fingering object is created,
1119 i.e., before @code{c2}, yields the following result:
1121 @lilypond[quote,relative=2,fragment,verbatim]
1122 \once \override Voice.Fingering #'padding = #3
1129 In this case, the context for this tweak is @context{Voice}. This
1130 fact can also be deduced from the program reference, for the page for
1131 the @internalsref{Fingering_engraver} plug-in says
1134 Fingering_engraver is part of contexts: @dots{} @b{@internalsref{Voice}}
1137 @node Objects connected to the input
1138 @subsection Objects connected to the input
1140 In some cases, it is possible to take a short-cut for tuning graphical
1141 objects. For objects that result directly from a piece of the input,
1142 you can use the @code{\tweak} function, for example
1144 @lilypond[relative=2,fragment,verbatim,ragged-right]
1147 \tweak #'color #red d
1149 \tweak #'duration-log #1 a
1150 >4-\tweak #'padding #10 -.
1153 As you can see, properties are set directly in the objects directly,
1154 without mentioning the grob name or context where this should be
1157 This technique only works for objects that are directly connected to
1158 an @internalsref{event} from the input, for example
1161 @item note heads, caused by chord-pitch.
1162 @item articulation signs, caused by articulation instructions
1165 It notably does not work for stems and accidentals (these are caused
1166 by note heads, not by music events) or clefs (these are not caused by
1167 music inputs, but rather by the change of a property value).
1170 @node Difficult tweaks
1171 @subsection Difficult tweaks
1173 There are a few classes of difficult adjustments.
1179 One type of difficult adjustment is the appearance of spanner objects,
1180 such as slur and tie. Initially, only one of these objects is created,
1181 and they can be adjusted with the normal mechanism. However, in some
1182 cases the spanners cross line breaks. If this happens, these objects
1183 are cloned. A separate object is created for every system that it is
1184 in. These are clones of the original object and inherit all
1185 properties, including @code{\override}s.
1188 In other words, an @code{\override} always affects all pieces of a
1189 broken spanner. To change only one part of a spanner at a line break,
1190 it is necessary to hook into the formatting process. The
1191 @code{after-line-breaking} callback contains the Scheme procedure that
1192 is called after the line breaks have been determined, and layout
1193 objects have been split over different systems.
1195 In the following example, we define a procedure
1196 @code{my-callback}. This procedure
1200 determines if we have been split across line breaks
1202 if yes, retrieves all the split objects
1204 checks if we are the last of the split objects
1206 if yes, it sets @code{extra-offset}.
1209 This procedure is installed into @internalsref{Tie}, so the last part
1210 of the broken tie is translated up.
1212 @lilypond[quote,verbatim,ragged-right]
1213 #(define (my-callback grob)
1215 ; have we been split?
1216 (orig (ly:grob-original grob))
1218 ; if yes, get the split pieces (our siblings)
1219 (siblings (if (ly:grob? orig)
1220 (ly:spanner-broken-into orig) '() )))
1222 (if (and (>= (length siblings) 2)
1223 (eq? (car (last-pair siblings)) grob))
1224 (ly:grob-set-property! grob 'extra-offset '(-2 . 5)))))
1227 \override Tie #'after-line-breaking =
1234 When applying this trick, the new @code{after-line-breaking} callback
1235 should also call the old one @code{after-line-breaking}, if there is
1236 one. For example, if using this with @code{Hairpin},
1237 @code{ly:hairpin::after-line-breaking} should also be called.
1240 @item Some objects cannot be changed with @code{\override} for
1241 technical reasons. Examples of those are @code{NonMusicalPaperColumn}
1242 and @code{PaperColumn}. They can be changed with the
1243 @code{\outputProperty} function, which works similar to @code{\once
1244 \override}, but uses a different syntax,
1248 #"Score.NonMusicalPaperColumn" % Grob name
1249 #'line-break-system-details % Property name
1250 #'((next-padding . 20)) % Value