@item
Page layout: changing the appearance of the spacing, line
breaks, and page dimensions. These modifications are discussed
-in @ref{Non-musical notation} and @ref{Spacing issues}.
+in @ref{Non-musical notation}, and @ref{Spacing issues}.
@end itemize
Internally, LilyPond uses Scheme (a LISP dialect) to provide
infrastructure. Overriding layout decisions in effect accesses the
program internals, which requires Scheme input. Scheme elements are
introduced in a @code{.ly} file with the hash mark
-@code{#}.@footnote{@ref{Scheme tutorial} contains a short tutorial
+@code{#}.@footnote{@ref{Scheme tutorial}, contains a short tutorial
on entering numbers, lists, strings, and symbols in Scheme.}
* Changing context default settings::
* Defining new contexts::
* Aligning contexts::
+* Vertical grouping of grobs::
@end menu
@subsection Contexts explained
When music is printed, a lot of notational elements must be added to the
-input. For example, compare the input and output of the following example:
+output. For example, compare the input and output of the following example:
@lilypond[quote,verbatim,relative=2,fragment]
cis4 cis2. g4
@code{NoteHead}, and @var{property} is an internal variable of the
formatting system (@q{grob property} or @q{layout property}). The latter is a
symbol, so it must be quoted. The subsection @ref{Constructing a
-tweak} explains what to fill in for @var{name}, @var{property}, and
+tweak}, explains what to fill in for @var{name}, @var{property}, and
@var{value}. Here we only discuss the functionality of this command.
The command
all stems are thickened.
Analogous to @code{\set}, the @var{context} argument may be left out,
-causing it to default to @context{Voice}, and adding @code{\once} applies
-the change during one timestep only
+causing the default context @context{Voice} to be used. Adding
+@code{\once} applies the change during one timestep only.
@lilypond[quote,fragment,verbatim,relative=2]
c4
@}
@end example
-Here @code{\Staff} takes the existing definition for context @context{Staff} from the
-identifier @code{\Staff}.
+The @code{\Staff} command brings in the existing definition of the
+staff context so that it can be modified.
The statements
@example
@}
@end example
-In the following discussion, the example input shown should go on the
-@dots{} in the previous fragment.
+In the following discussion, the example input shown should go in place
+of the @dots{} in the previous fragment.
-First the context's name is defined. Instead of @context{Voice} it
-will be called @context{ImproVoice},
+First it is necessary to define a name for the new context:
@example
\name ImproVoice
\alias Voice
@end example
-The context will print notes, and instructive texts
+The context will print notes and instructive texts, so we need to add
+the engravers which provide this functionality,
@example
\consists Note_heads_engraver
\consists Text_engraver
@end example
-but only on the center line,
+but we only need this on the center line,
@example
\consists Pitch_squash_engraver
@end lilypond
+@node Vertical grouping of grobs
+@subsection Vertical grouping of grobs
+
+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 The \override command
-@section The \override command
+@section The @code{\override} command
In the previous section, we have already touched on a command that
changes layout details: the @code{\override} command. In this section,
-we will look in more detail at how to use the command in practice.
+we will look in more detail at how to use the command in practice. The
+general syntax of this command is:
+
+@example
+\override @var{context}.@var{layout_object} #'@var{layout_property} = #@var{value}
+@end example
+This will set the @var{layout_property} of the specified @var{layout_object},
+which is a member of the @var{context}, to the @var{value}.
@menu
* Constructing a tweak::
* Layout interfaces::
* Determining the grob property::
* Objects connected to the input::
-* \set vs. \override::
+* Using Scheme code instead of \tweak::
+* \set versus \override::
* Difficult tweaks::
@end menu
@end example
@noindent
-This means that we must determine these bits of information:
+To construct this tweak we must determine these bits of information:
@itemize
@item the context: here @context{Voice}.
@funindex \override
@cindex internal documentation
+For many properties, regardless of the data type of the property, setting the
+property to false ( @code{##f} ) will result in turning it off, causing
+Lilypond to ignore that property entirely. This is particularly useful for
+turning off grob properties which may otherwise be causing problems.
+
We demonstrate how to glean this information from the notation manual
and the program reference.
+
+
@node Navigating the program reference
@subsection Navigating the program reference
manual.
@end ignore
+@ifnothtml
+The programmer's reference is available as an HTML document. It is
+highly recommended that you read it in HTML form, either online or
+by downloading the HTML documentation. This section will be much more
+difficult to understand if you are using the
+PDF manual.
+@end ifnothtml
+
Follow the link to @internalsref{Fingering}. At the top of the
page, you will see
@internalsref{New_fingering_engraver}.
@end quotation
-By clicking around in the program reference, we can follow the
-flow of information within the program, following links like this:
+By following related links inside the program reference, we can follow the
+flow of information within the program:
@itemize @bullet
@end quotation
@noindent
-which means that the number will be kept at a distance of at least 0.6
+which means that the number will be kept at a distance of at least 0.5
of the note head.
@funindex \tweak
In some cases, it is possible to take a short-cut for tuning graphical
-objects. For objects that result directly from a piece of the input,
+objects. For objects that result directly from a piece of the input,
you can use the @code{\tweak} function, for example
@lilypond[relative=2,fragment,verbatim,ragged-right]
>4-\tweak #'padding #10 -.
@end lilypond
-As you can see, properties are set directly in the objects directly,
+As you can see, properties are set in the objects directly,
without mentioning the grob name or context where this should be
applied.
an @internalsref{event} from the input, for example
@itemize @bullet
-@item note heads, caused by chord-pitch (i.e., notes inside a chord).
-@item articulation signs, caused by articulation instructions.
+@item note heads, caused by chord-pitch (i.e., notes inside a chord)
+@item articulation signs, caused by articulation instructions
@end itemize
It notably does not work for stems and accidentals (these are caused
@end example
@noindent
-will not change color. See @ref{Displaying music expressions} for
+does not change color. See @ref{Displaying music expressions}, for
details.
-@node \set vs. \override
-@subsection \set vs. \override
+@node Using Scheme code instead of \tweak
+@subsection Using Scheme code instead of @code{\tweak}
+
+The main disadvantage of @code{\tweak} is its syntactical
+inflexibility. For example, the following produces a syntax error.
+
+@example
+F = \tweak #'font-size #-3 -\flageolet
+
+\relative c'' @{
+ c4^\F c4_\F
+@}
+@end example
+
+@noindent
+With other words, @code{\tweak} doesn't behave like an articulation
+regarding the syntax; in particular, it can't be attached with
+@samp{^} and @samp{_}.
+
+Using Scheme, this problem can be circumvented. The route to the
+result is given in @ref{Adding articulation to notes (example)},
+especially how to use @code{\displayMusic} as a helping guide.
+
+@example
+F = #(let ((m (make-music 'ArticulationEvent
+ 'articulation-type "flageolet")))
+ (set! (ly:music-property m 'tweaks)
+ (acons 'font-size -3
+ (ly:music-property m 'tweaks)))
+ m)
+
+\relative c'' @{
+ c4^\F c4_\F
+@}
+@end example
+
+@noindent
+Here, the @code{tweaks} properties of the flageolet object
+@samp{m} (created with @code{make-music}) are extracted with
+@code{ly:music-property}, a new key-value pair to change the
+font size is prepended to the property list with the
+@code{acons} Scheme function, and the result is finally
+written back with @code{set!}. The last element of the
+@code{let} block is the return value, @samp{m} itself.
+
+
+@node \set versus \override
+@subsection @code{\set} vs. @code{\override}
We have seen two methods of changing properties: @code{\set} and
@code{\override}. There are actually two different kinds of
@item Some objects cannot be changed with @code{\override} for
-technical reasons. Examples of those are @code{NonMusicalPaperColumn}
+technical reasons. Examples of those are @code{NonMusicalPaperColumn}
and @code{PaperColumn}. They can be changed with the
-@code{\outputProperty} function, which works similar to @code{\once
-\override}, but uses a different syntax,
+@code{\overrideProperty} function, which works similar to @code{\once
+\override}, but uses a different syntax.
@example
-\outputProperty
+\overrideProperty
#"Score.NonMusicalPaperColumn" % Grob name
#'line-break-system-details % Property name
#'((next-padding . 20)) % Value
@end example
+Note, however, that @code{\override}, applied to
+@code{NoteMusicalPaperColumn} and @code{PaperColumn}, still works as
+expected within @code{\context} blocks.
+
@end itemize
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