+
+@node Special considerations
+@unnumberedsubsubsec Special considerations
+
+@strong{@emph{Visibility following explicit changes}}
+
+@cindex key signature, visibility following explicit change
+@cindex explicitKeySignatureVisibility
+@cindex clef, visibility following explicit change
+@cindex explicitClefVisibility
+
+The @code{break-visibility} property controls the visibility of
+key signatures and changes of clef only at the start of lines,
+i.e. after a break. It has no effect on the visibility of the
+key signature or clef following an explicit key change or an
+explicit clef change within or at the end of a line. In the
+following example the key signature following the explicit change
+to B-flat major is still visible, even though @code{all-invisible}
+is set.
+
+@lilypond[quote,verbatim,relative=1,ragged-right]
+\key g \major
+f4 g a b
+% Try to remove all key signatures
+\override Staff.KeySignature #'break-visibility = #all-invisible
+\key bes \major
+f4 g a b
+\break
+f4 g a b
+f4 g a b
+@end lilypond
+
+The visibility of such explicit key signature and clef changes is
+controlled by the @code{explicitKeySignatureVisibility} and
+@code{explicitClefVisibility} properties. These are the equivalent
+of the @code{break-visibility} property and both take a vector of
+three booleans or the predefined functions listed above, exactly like
+@code{break-visibility}. Both are properties of the Staff context,
+not the layout objects themselves, and so they are set using the
+@code{\set} command. Both are set by default to @code{all-visible}.
+These properties control only the visibility of key signatures and
+clefs resulting from explicit changes and do not affect key
+signatures and clefs at the beginning of lines;
+@code{break-visibility} must still be overridden in the appropriate
+object to remove these.
+
+@lilypond[quote,verbatim,relative=1,ragged-right]
+\key g \major
+f4 g a b
+\set Staff.explicitKeySignatureVisibility = #all-invisible
+\override Staff.KeySignature #'break-visibility = #all-invisible
+\key bes \major
+f4 g a b \break
+f4 g a b
+f4 g a b
+@end lilypond
+
+@strong{@emph{Visibility of cautionary accidentals}}
+
+To remove the cautionary accidentals printed at an explicit key
+change, set the Staff context property @code{printKeyCancellation}
+to @code{#f}:
+
+@lilypond[quote,verbatim,relative=1,ragged-right]
+\key g \major
+f4 g a b
+\set Staff.explicitKeySignatureVisibility = #all-invisible
+\set Staff.printKeyCancellation = ##f
+\override Staff.KeySignature #'break-visibility = #all-invisible
+\key bes \major
+f4 g a b \break
+f4 g a b
+f4 g a b
+@end lilypond
+
+With these overrides only the accidentals before the notes remain
+to indicate the change of key.
+
+@c TODO Add visibility of cautionary accidentals before notes
+
+@strong{@emph{Automatic bars}}
+
+@cindex automaticBars
+@cindex bar lines, suppressing
+
+As a special case, the printing of bar lines can also be turned off
+by setting the @code{automaticBars} property in the Score context.
+If set to @code{#f}, bar lines will not be printed automatically;
+they must be explicitly created with a @code{\bar} command. Unlike
+the @code{\cadenzaOn} predefined command, measures are still counted.
+Bar generation will resume according to that count if this property
+is later set to @code{#t}. When set to @code{#f}, line breaks can
+occur only at explicit @code{\bar} commands.
+
+@c TODO Add example
+
+@strong{@emph{Octavated clefs}}
+
+@cindex octavated clefs, visibility of
+@cindex visibility of octavated clefs
+@cindex clefs, visibility of octavation
+
+The small octavation symbol on octavated clefs is produced by the
+@code{OctavateEight} layout object. Its visibility is controlled
+independently from that of the @code{Clef} object, so it is
+necessary to apply any required @code{break-visibility} overrides
+to both the @code{Clef} and the @code{OctavateEight} layout objects
+to fully suppress such clef symbols at the start of each line.
+
+For explicit clef changes, the @code{explicitClefVisibility}
+property controls both the clef symbol and any octavation symbol
+associated with it.
+
+
+@seealso
+Learning Manual:
+@rlearning{Visibility and color of objects}
+
+
+@node Line styles
+@subsection Line styles
+
+@c TODO: split the following explanations between expressive marks and
+@c text-related stuff. Perhaps create a new subsection named
+@c "Spanner limits", "Spanner boundaries"? -vv
+
+Some performance indications, e.g., @i{rallentando} and
+@i{accelerando} and @i{trills} are written as text and are
+extended over many measures with lines, sometimes dotted or wavy.
+
+These all use the same routines as the glissando for drawing the
+texts and the lines, and tuning their behavior is therefore also
+done in the same way. It is done with a spanner, and the routine
+responsible for drawing the spanners is
+@code{ly:line-interface::print}. This routine determines the
+exact location of the two @i{span points} and draws a line in
+between, in the style requested.
+
+Here is an example of the different line styles available, and how
+to tune them.
+
+@lilypond[relative=2,ragged-right,verbatim,fragment]
+d2 \glissando d'2
+\once \override Glissando #'style = #'dashed-line
+d,2 \glissando d'2
+\override Glissando #'style = #'dotted-line
+d,2 \glissando d'2
+\override Glissando #'style = #'zigzag
+d,2 \glissando d'2
+\override Glissando #'style = #'trill
+d,2 \glissando d'2
+@end lilypond
+
+The information that determines the end-points is computed
+on-the-fly for every graphic object, but it is possible to
+override these.
+
+@lilypond[relative=2,ragged-right,verbatim,fragment]
+e2 \glissando f
+\once \override Glissando #'bound-details #'right #'Y = #-2
+e2 \glissando f
+@end lilypond
+
+The @code{Glissando} object, like any other using the
+@code{ly:line-interface::print} routine, carries a nested
+association list. In the above statement, the value for @code{Y}
+is set to @code{-2} for the association list corresponding to the
+right end point. Of course, it is also possible to adjust the
+left side with @code{left} instead of @code{right}.
+
+If @code{Y} is not set, the value is computed from the vertical
+position of right attachment point of the spanner.
+
+In case of a line break, the values for the span-points are
+extended with contents of the @code{left-broken} and
+@code{right-broken} sublists, for example
+
+@lilypond[relative=2,ragged-right,verbatim,fragment]
+\override Glissando #'breakable = ##T
+\override Glissando #'bound-details #'right-broken #'Y = #-3
+c1 \glissando \break
+f1
+@end lilypond
+
+The following properties can be used for the
+
+@table @code
+@item Y
+This sets the Y-coordinate of the end point, in staff space. By
+default, it is the center of the bound object, so for a glissando
+it points to the vertical center of the note head.
+
+For horizontal spanners, such as text spanner and trill spanners,
+it is hardcoded to 0.
+
+@item attach-dir
+This determines where the line starts and ends in X-direction,
+relative to the bound object. So, a value of @code{-1} (or
+@code{LEFT}) makes the line start/end at the left side of the note
+head it is attached to.
+
+@item X
+This is the absolute coordinate of the end point. It is usually
+computed on the fly, and there is little use in overriding it.
+
+@item stencil
+Line spanners may have symbols at the beginning or end, which is
+contained in this sub-property. This is for internal use, it is
+recommended to use @code{text}.
+
+@item text
+This is a markup that is evaluated to yield stencil. It is used
+to put @i{cresc.} and @i{tr} on horizontal spanners.
+
+@lilypond[quote,ragged-right,fragment,relative=2,verbatim]
+\override TextSpanner #'bound-details #'left #'text
+ = \markup { \small \bold Slower }
+c2\startTextSpan b c a\stopTextSpan
+@end lilypond
+
+@item stencil-align-dir-y
+@item stencil-offset
+Without setting this, the stencil is simply put there at the
+end-point, as defined by the @code{X} and @code{Y} sub properties.
+Setting either @code{stencil-align-dir-y} or @code{stencil-offset}
+will move the symbol at the edge relative to the end point of the
+line
+
+@lilypond[relative=1,fragment,verbatim]
+\override TextSpanner #'bound-details
+ #'left #'stencil-align-dir-y = #DOWN
+\override TextSpanner #'bound-details
+ #'right #'stencil-align-dir-y = #UP
+
+\override TextSpanner #'bound-details
+ #'left #'text = #"gggg"
+\override TextSpanner #'bound-details
+ #'right #'text = #"hhhh"
+c4^\startTextSpan c c c \stopTextSpan
+@end lilypond
+
+@item arrow
+Setting this sub property to @code{#t} produce an arrowhead at the
+end of the line.
+
+@item padding
+This sub property controls the space between the specified
+end-point of the line and the actual end. Without padding, a
+glissando would start and end in the center of each note head.
+
+@end table
+
+@c TODO: Move to 5.4.4
+
+The music function \endSpanners terminates spanners and hairpins
+after exactly one note.
+
+@lilypond[verbatim,quote,ragged-right,relative=2,fragment]
+\endSpanners
+c2 \startTextSpan c2
+c2 \< c2
+@end lilypond
+
+When using \endSpanners it is not necessary to close
+\startTextSpan with \stopTextSpan, nor is it necessary to close
+hairpins with \!.
+
+
+
+@seealso
+
+Internals Reference: @rinternals{TextSpanner},
+@rinternals{Glissando}, @rinternals{VoiceFollower},
+@rinternals{TrillSpanner},
+@rinternals{line-spanner-interface}.
+
+
+@node Rotating objects
+@subsection Rotating objects
+
+Both layout objects and elements of markup text can be rotated by
+any angle about any point, but the method of doing so differs.
+
+@menu
+* Rotating layout objects::
+* Rotating markup::
+@end menu
+
+@node Rotating layout objects
+@unnumberedsubsubsec Rotating layout objects
+
+@cindex rotating objects
+@cindex objects, rotating
+
+All layout objects which support the @code{grob-interface} can be
+rotated by setting their @code{rotation} property. This takes a
+list of three items: the angle of rotation counter-clockwise,
+and the x and y coordinates of the point relative to the object's
+reference point about which the rotation is to be performed. The
+angle of rotation is specified in degrees and the coordinates in
+staff-spaces.
+
+The angle of rotation and the coordinates of the rotation point must
+be determined by trial and error.
+
+@cindex hairpins, angled
+@cindex angled hairpins
+
+There are only a few situations where the rotation of layout
+objects is useful; the following example shows one situation where
+they may be:
+
+@lilypond[quote,verbatim,relative=1]
+g4\< e' d' f\!
+\override Hairpin #'rotation = #'(20 -1 0)
+g,,4\< e' d' f\!
+@end lilypond
+
+@node Rotating markup
+@unnumberedsubsubsec Rotating markup
+
+All markup text can be rotated to lie at any angle by prefixing it
+with the @code{\rotate} command. The command takes two arguments:
+the angle of rotation in degrees counter-clockwise and the text to
+be rotated. The extents of the text are not rotated: they take
+their values from the extremes of the x and y coordinates of the
+rotated text. In the following example the
+@code{outside-staff-priority} property for text is set to @code{#f}
+to disable the automatic collision avoidance, which would push some
+of the text too high.
+
+@lilypond[quote,verbatim,relative=1]
+\override TextScript #'outside-staff-priority = ##f
+g4^\markup { \rotate #30 "a G" }
+b^\markup { \rotate #30 "a B" }
+des^\markup { \rotate #30 "a D-Flat" }
+fis^\markup { \rotate #30 "an F-Sharp" }
+@end lilypond
+
+
+@node Aligning objects
+@subsection Aligning objects
+
+@c FIXME Write this section
+
+
+@node Advanced tweaks
+@section Advanced tweaks
+
+@menu
+* Vertical grouping of grobs::
+* Modifying ends of spanners::
+* Modifying stencils::
+* Modifying shapes::
+@end menu
+
+
+
+
+@node Vertical grouping of grobs
+@subsection Vertical grouping of grobs
+
+@c FIXME Expand this section
+
+The VerticalAlignment and VerticalAxisGroup grobs work together.
+VerticalAxisGroup groups together different grobs like Staff, Lyrics,
+etc. VerticalAlignment then vertically aligns the different grobs
+grouped together by VerticalAxisGroup. There is usually only one
+VerticalAlignment per score but every Staff, Lyrics, etc. has its own
+VerticalAxisGroup.
+
+
+@node Modifying ends of spanners
+@subsection Modifying ends of spanners
+
+@c FIXME Write this section
+
+@node Modifying stencils
+@subsection Modifying stencils
+
+@c FIXME Write this section
+
+@node Modifying shapes
+@subsection Modifying shapes
+
+@c FIXME Write this section
+@c Discussion of Bezier curves and the control-points property
+
+@node Discussion of specific tweaks
+@section Discussion of specific tweaks
+
+@menu
+* old Contexts explained::
+@end menu
+
+
+@node old Contexts explained
+@subsection old Contexts explained
+
+@c FIXME Delete this section? It is in LM
+@c Or leave heading and go on from LM?
+
+When music is printed, a lot of notational elements must be added to the
+output. For example, compare the input and output of the following example:
+
+@lilypond[quote,verbatim,relative=2,fragment]
+cis4 cis2. g4
+@end lilypond
+
+The input is rather sparse, but in the output, bar lines, accidentals,
+clef, and time signature are added. LilyPond @emph{interprets} the
+input. During this step, the musical information is inspected in time
+order, similar to reading a score from left to right. While reading
+the input, the program remembers where measure boundaries are, and which
+pitches require explicit accidentals. This information can be presented on
+several levels. For example, the effect of an accidental is limited
+to a single staff, while a bar line must be synchronized across the
+entire score.
+
+Within LilyPond, these rules and bits of information are grouped in
+@emph{Contexts}. Some examples of contexts are @code{Voice},
+@code{Staff}, and @code{Score}. They are hierarchical, for
+example: a @code{Staff} can contain many @code{Voice}s, and a
+@code{Score} can contain many @code{Staff} contexts.
+
+@quotation
+@sourceimage{context-example,5cm,,}
+@end quotation
+
+Each context has the responsibility for enforcing some notation rules,
+creating some notation objects and maintaining the associated
+properties. For example, the @code{Voice} context may introduce an
+accidental and then the @code{Staff} context maintains the rule to
+show or suppress the accidental for the remainder of the measure. The
+synchronization of bar lines is handled at @code{Score} context.
+
+However, in some music we may not want the bar lines to be
+synchronized -- consider a polymetric score in 4/4 and 3/4 time. In
+such cases, we must modify the default settings of the @code{Score}
+and @code{Staff} contexts.
+
+For very simple scores, contexts are created implicitly, and you need
+not be aware of them. For larger pieces, such as anything with more
+than one staff, they must be
+created explicitly to make sure that you get as many staves as you
+need, and that they are in the correct order. For typesetting pieces
+with specialized notation, it can be useful to modify existing or
+to define new contexts.
+
+
+A complete description of all available contexts is in the program
+reference, see
+@ifhtml
+@rinternals{Contexts}.
+@end ifhtml
+@ifnothtml
+Translation @expansion{} Context.
+@end ifnothtml
+
+@c [TODO: describe propagation]
+
+
+