+This manual: @ref{Changing context default settings}.
+
+
+@node Breaks
+@section Breaks
+
+@menu
+* Line breaking::
+* Page breaking::
+* Optimal page breaking::
+* Optimal page turning::
+* Minimal page breaking::
+* Explicit breaks::
+* Using an extra voice for breaks::
+@end menu
+
+@node Line breaking
+@subsection Line breaking
+
+@cindex line breaks
+@cindex breaking lines
+
+Line breaks are normally determined automatically. They are chosen
+so that lines look neither cramped nor loose, and consecutive
+lines have similar density. Occasionally you might want to
+override the automatic breaks; you can do this by specifying
+@code{\break}. This will force a line break at this point. However,
+line breaks can only occur at the end of @q{complete} bars, i.e.,
+where there are no notes or tuplets left @q{hanging} over the bar
+line. If you want to have a line break where there is no bar line,
+you can force an invisible bar line by entering @code{\bar ""},
+although again there must be no notes left hanging over in any of
+the staves at this point, or it will be ignored.
+
+The opposite command, @code{\noBreak}, forbids a line break at the
+bar line where it is inserted.
+
+The most basic settings influencing line spacing are @code{indent}
+and @code{line-width}. They are set in the @code{\layout} block.
+They control the indentation of the first line of music, and the
+lengths of the lines.
+
+If @code{ragged-right} is set to true in the @code{\layout} block,
+then systems end at their natural horizontal length, instead of
+being spread horizontally to fill the whole line. This is useful
+for short fragments, and for checking how tight the natural
+spacing is.
+
+@c TODO Check and add para on default for ragged-right
+
+The option @code{ragged-last} is similar to @code{ragged-right},
+but affects only the last line of the piece.
+
+@example
+\layout @{
+indent = #0
+line-width = #150
+ragged-last = ##t
+@}
+@end example
+
+
+
+@cindex regular line breaks
+@cindex four bar music.
+
+For line breaks at regular intervals use @code{\break} separated by
+skips and repeated with @code{\repeat}. For example, this would
+cause the following 28 measures (assuming 4/4 time) to be broken
+every 4 measures, and only there:
+
+@example
+<< \repeat unfold 7 @{
+ s1 \noBreak s1 \noBreak
+ s1 \noBreak s1 \break @}
+ @emph{the real music}
+>>
+@end example
+
+@predefined
+
+@code{\break}, and @code{\noBreak}.
+@funindex \break
+@funindex \noBreak
+
+@seealso
+
+Internals: @rinternals{LineBreakEvent}.
+
+@c TODO Check this
+A linebreaking configuration can be saved as a @code{.ly} file
+automatically. This allows vertical alignments to be stretched to
+fit pages in a second formatting run. This is fairly new and
+complicated. More details are available in
+@rlsr{Spacing}.
+
+@knownissues
+
+Line breaks can only occur if there is a @q{proper} bar line. A note
+which is hanging over a bar line is not proper, such as
+
+@lilypond[quote,ragged-right,relative=2,fragment,verbatim]
+c4 c2 << c2 {s4 \break } >> % this does nothing
+c2 c4 | % a break here would work
+c4 c2 c4 ~ \break % as does this break
+c4 c2 c4
+@end lilypond
+
+This can be avoided by removing the @code{Forbid_line_break_engraver}.
+Note that manually forced line breaks have to be added in parallel
+with the music.
+
+@lilypond[quote,ragged-right,verbatim]
+\new Voice \with {
+ \remove Forbid_line_break_engraver
+} {
+ c4 c2 << c2 {s4 \break } >> % now the break is allowed
+ c2 c4
+}
+@end lilypond
+
+Similarly, line breaks are normally forbidden when beams cross bar
+lines. This behavior can be changed by setting
+@code{\override Beam #'breakable = ##t}.
+
+
+@node Page breaking
+@subsection Page breaking
+
+The default page breaking may be overridden by inserting
+@code{\pageBreak} or @code{\noPageBreak} commands. These commands are
+analogous to @code{\break} and @code{\noBreak}. They should be
+inserted at a bar line. These commands force and forbid a page-break
+from happening. Of course, the @code{\pageBreak} command also forces
+a line break.
+
+The @code{\pageBreak} and @code{\noPageBreak} commands may also be
+inserted at top-level, between scores and top-level markups.
+
+There are also analogous settings to @code{ragged-right} and
+@code{ragged-last} which have the same effect on vertical spacing:
+@code{ragged-bottom} and @code{ragged-last-bottom}. If set to
+@code{##t} the systems on all pages or just the last page
+respectively will not be justified vertically.
+
+For more details see @ref{Vertical spacing}.
+
+Page breaks are computed by the @code{page-breaking} function. LilyPond
+provides three algorithms for computing page breaks,
+@code{ly:optimal-breaking}, @code{ly:page-turn-breaking} and
+@code{ly:minimal-breaking}. The default is @code{ly:optimal-breaking},
+but the value can be changed in the @code{\paper} block:
+
+@example
+\paper@{
+ #(define page-breaking ly:page-turn-breaking)
+@}
+@end example
+
+@c TODO Check this -td
+The old page breaking algorithm is called
+@code{optimal-page-breaks}. If you are having trouble with the new page
+breakers, you can enable the old one as a workaround.
+
+@predefined
+
+@funindex \pageBreak
+@code{\pageBreak}
+@funindex \noPageBreak
+@code{\noPageBreak}
+
+
+@node Optimal page breaking
+@subsection Optimal page breaking
+
+@funindex ly:optimal-breaking
+
+The @code{ly:optimal-breaking} function is LilyPond's default method of
+determining page breaks. It attempts to find a page breaking that minimizes
+cramping and stretching, both horizontally and vertically. Unlike
+@code{ly:page-turn-breaking}, it has no concept of page turns.
+
+
+@node Optimal page turning
+@subsection Optimal page turning
+
+@funindex ly:page-turn-breaking
+
+Often it is necessary to find a page breaking configuration so that there is
+a rest at the end of every second page. This way, the musician can turn the
+page without having to miss notes. The @code{ly:page-turn-breaking} function
+attempts to find a page breaking minimizing cramping and stretching, but with
+the additional restriction that it is only allowed to introduce page turns
+in specified places.
+
+There are two steps to using this page breaking function. First, you
+must enable it in the @code{\paper} block, as explained in @ref{Page
+breaking}. Then you must tell the function where you would like to allow
+page breaks.
+
+There are two ways to achieve the second step. First, you can specify each
+potential page turn manually, by inserting @code{\allowPageTurn} into your
+input file at the appropriate places.
+
+If this is too tedious, you can add a @code{Page_turn_engraver} to a Staff or
+Voice context. The @code{Page_turn_engraver} will scan the context for
+sections without notes (note that it does not scan for rests; it scans for
+the absence of notes. This is so that single-staff polyphony with rests in one
+of the parts does not throw off the @code{Page_turn_engraver}). When it finds
+a sufficiently long section without notes, the @code{Page_turn_engraver} will
+insert an @code{\allowPageTurn} at the final bar line in that section, unless
+there is a @q{special} bar line (such as a double bar), in which case the
+@code{\allowPageTurn} will be inserted at the final @q{special} bar line in
+the section.
+
+@funindex minimumPageTurnLength
+The @code{Page_turn_engraver} reads the context property
+@code{minimumPageTurnLength} to determine how long a note-free section must
+be before a page turn is considered. The default value for
+@code{minimumPageTurnLength} is @code{#(ly:make-moment 1 1)}. If you want
+to disable page turns, you can set it to something very large.
+
+@example
+\new Staff \with @{ \consists "Page_turn_engraver" @}
+@{
+ a4 b c d |
+ R1 | % a page turn will be allowed here
+ a4 b c d |
+ \set Staff.minimumPageTurnLength = #(ly:make-moment 5 2)
+ R1 | % a page turn will not be allowed here
+ a4 b r2 |
+ R1*2 | % a page turn will be allowed here
+ a1
+@}
+@end example
+
+@funindex minimumRepeatLengthForPageTurn
+The @code{Page_turn_engraver} detects volta repeats. It will only allow a page
+turn during the repeat if there is enough time at the beginning and end of the
+repeat to turn the page back. The @code{Page_turn_engraver} can also disable
+page turns if the repeat is very short. If you set the context property
+@code{minimumRepeatLengthForPageTurn} then the @code{Page_turn_engraver} will
+only allow turns in repeats whose duration is longer than this value.
+
+The page turning commands, @code{\pageTurn}, @code{\noPageTurn} and
+@code{\allowPageTurn}, may also be used at top-level, between scores and
+top-level markups.
+
+@predefined
+
+@funindex \pageTurn
+@code{\pageTurn}
+@funindex \noPageTurn
+@code{\noPageTurn}
+@funindex \allowPageTurn
+@code{\allowPageTurn}
+
+@knownissues
+
+There should only be one @code{Page_turn_engraver} in a score. If there is more
+than one, they will interfere with each other.
+
+@node Minimal page breaking
+@subsection Minimal page breaking
+
+@funindex ly:minimal-breaking
+
+The @code{ly:minimal-breaking} function performs minimal computations to
+calculate the page breaking: it fills a page with as many systems as
+possible before moving to the next one. Thus, it may be preferred for
+scores with many pages, where the other page breaking functions could be
+too slow or memory demanding, or a lot of texts. It is enabled using:
+
+@example
+\paper @{
+ #(define page-breaking ly:minimal-breaking)
+@}
+@end example
+
+@node Explicit breaks
+@subsection Explicit breaks
+
+Lily sometimes rejects explicit @code{\break} and @code{\pageBreak}
+commands. There are two commands to override this behavior:
+
+@example
+\override NonMusicalPaperColumn #'line-break-permission = ##f
+\override NonMusicalPaperColumn #'page-break-permission = ##f
+@end example
+
+When @code{line-break-permission} is overridden to false, Lily will insert
+line breaks at explicit @code{\break} commands and nowhere else. When
+@code{page-break-permission} is overridden to false, Lily will insert
+page breaks at explicit @code{\pageBreak} commands and nowhere else.
+
+@lilypond[quote,verbatim]
+\paper {
+ indent = #0
+ ragged-right = ##t
+ ragged-bottom = ##t
+}
+
+\score {
+ \new Score \with {
+ \override NonMusicalPaperColumn #'line-break-permission = ##f
+ \override NonMusicalPaperColumn #'page-break-permission = ##f
+ } {
+ \new Staff {
+ \repeat unfold 2 { c'8 c'8 c'8 c'8 } \break
+ \repeat unfold 4 { c'8 c'8 c'8 c'8 } \break
+ \repeat unfold 6 { c'8 c'8 c'8 c'8 } \break
+ \repeat unfold 8 { c'8 c'8 c'8 c'8 } \pageBreak
+ \repeat unfold 8 { c'8 c'8 c'8 c'8 } \break
+ \repeat unfold 6 { c'8 c'8 c'8 c'8 } \break
+ \repeat unfold 4 { c'8 c'8 c'8 c'8 } \break
+ \repeat unfold 2 { c'8 c'8 c'8 c'8 }
+ }
+ }
+}
+@end lilypond
+
+
+@node Using an extra voice for breaks
+@subsection Using an extra voice for breaks
+
+Line- and page-breaking information usually appears within note entry directly.
+
+@example
+\new Score @{
+ \new Staff @{
+ \repeat unfold 2 @{ c'4 c'4 c'4 c'4 @}
+ \break
+ \repeat unfold 3 @{ c'4 c'4 c'4 c'4 @}
+ @}
+@}
+@end example
+
+This makes @code{\break} and @code{\pageBreak} commands easy to enter but mixes
+music entry with information that specifies how music should lay out
+on the page. You can keep music entry and line- and page-breaking
+information in two separate places by introducing an extra voice to
+contain the breaks. This extra voice
+contains only skips together with @code{\break}, @code{pageBreak} and other
+breaking layout information.
+
+@lilypond[quote,verbatim]
+\new Score {
+ \new Staff <<
+ \new Voice {
+ s1 * 2 \break
+ s1 * 3 \break
+ s1 * 6 \break
+ s1 * 5 \break
+ }
+ \new Voice {
+ \repeat unfold 2 { c'4 c'4 c'4 c'4 }
+ \repeat unfold 3 { c'4 c'4 c'4 c'4 }
+ \repeat unfold 6 { c'4 c'4 c'4 c'4 }
+ \repeat unfold 5 { c'4 c'4 c'4 c'4 }
+ }
+ >>
+}
+@end lilypond
+
+This pattern becomes especially helpful when overriding
+@code{line-break-system-details} and the other useful but long properties of
+@code{NonMusicalPaperColumnGrob}, as explained in @ref{Vertical spacing}.
+
+@lilypond[quote,verbatim]
+\new Score {
+ \new Staff <<
+ \new Voice {
+
+ \overrideProperty "Score.NonMusicalPaperColumn"
+ #'line-break-system-details #'((Y-offset . 0))
+ s1 * 2 \break
+
+ \overrideProperty "Score.NonMusicalPaperColumn"
+ #'line-break-system-details #'((Y-offset . 35))
+ s1 * 3 \break
+
+ \overrideProperty "Score.NonMusicalPaperColumn"
+ #'line-break-system-details #'((Y-offset . 70))
+ s1 * 6 \break
+
+ \overrideProperty "Score.NonMusicalPaperColumn"
+ #'line-break-system-details #'((Y-offset . 105))
+ s1 * 5 \break
+ }
+ \new Voice {
+ \repeat unfold 2 { c'4 c'4 c'4 c'4 }
+ \repeat unfold 3 { c'4 c'4 c'4 c'4 }
+ \repeat unfold 6 { c'4 c'4 c'4 c'4 }
+ \repeat unfold 5 { c'4 c'4 c'4 c'4 }
+ }
+ >>
+}
+@end lilypond
projects / lilypond.git / blobdiff