X-Git-Url: https://git.donarmstrong.com/?a=blobdiff_plain;f=Documentation%2Fuser%2Fprogramming-interface.itely;h=efd842df2531bdea894218ae78ea19d89f7dff18;hb=35b0fbb1259956969f25dc2ee09872193a97b61c;hp=e55d26471bb677b0bbf0ceadd2b2346ccea27240;hpb=e3fbf0543b38e5c20155cef9dc48d70e91da45c2;p=lilypond.git

diff --git a/Documentation/user/programming-interface.itely b/Documentation/user/programming-interface.itely
index e55d26471b..efd842df25 100644
--- a/Documentation/user/programming-interface.itely
+++ b/Documentation/user/programming-interface.itely
@@ -7,12 +7,14 @@
     version that you are working on.  See TRANSLATION for details.
 @end ignore
 
+@c \version "2.11.61"
+
 @node Interfaces for programmers
 @chapter Interfaces for programmers
 
 Advanced tweaks may be performed by using Scheme.  If you are
 not familiar with Scheme, you may wish to read our
-@ref{Scheme tutorial}.
+@rlearning{Scheme tutorial}.
 
 @menu
 * Music functions::             
@@ -20,7 +22,9 @@ not familiar with Scheme, you may wish to read our
 * Building complicated functions::  
 * Markup programmer interface::  
 * Contexts for programmers::    
-* Scheme procedures as properties::  
+* Scheme procedures as properties::
+* Using Scheme code instead of \tweak::  
+* Difficult tweaks::
 @end menu
 
 
@@ -230,7 +234,7 @@ turning off Point and Click).  To do this, we return a @code{void}
 music expression.
 
 That is why the form
-that is returned is the @code{(make-music ...)}. With the
+that is returned is the @code{(make-music ...)}.  With the
 @code{'void} property set to @code{#t}, the parser is told to
 actually disregard this returned music
 expression.  Thus the important part of the void music function is the
@@ -251,7 +255,7 @@ noPointAndClick =
 @subsection Functions without arguments
 
 In most cases a function without arguments should be written
-with an identifier,
+with an variable,
 
 @example
 dolce = \markup@{ \italic \bold dolce @}
@@ -263,13 +267,13 @@ without arguments,
 @example
 displayBarNum =
 #(define-music-function (parser location) ()
-   (if (eq? #t (ly:get-option display-bar-numbers))
+   (if (eq? #t (ly:get-option 'display-bar-numbers))
        #@{ \once \override Score.BarNumber #'break-visibility = ##f #@}
        #@{#@}))
 @end example
 
 To actually display bar numbers where this function is called,
-invoke lilypond with
+invoke @command{lilypond} with
 
 @example
 lilypond -d display-bar-numbers FILENAME.ly
@@ -359,7 +363,7 @@ traLaLa = { c'4 d'4 }
 Due to parser lookahead
 
 In this example, the assignment happens after parser has verified that
-nothing interesting happens after @code{traLaLa = @{ ... @}}. Without
+nothing interesting happens after @code{traLaLa = @{ ... @}}.  Without
 the dummy statement in the above example, the @code{newLa} definition
 is executed before @code{traLaLa} is defined, leading to a syntax
 error.
@@ -389,9 +393,9 @@ define some Scheme code in a macro (to be called later), use
 @end example
 
 
-@refbugs
+@knownissues
 
-Mixing Scheme and LilyPond identifiers is not possible with the
+Mixing Scheme and LilyPond variables is not possible with the
 @code{--safe} option.
 
 
@@ -404,21 +408,21 @@ it takes up time.  Time is a rational number that measures the length
 of a piece of music in whole notes.
 
 A music object has three kinds of types:
-@itemize @bullet
+@itemize
 @item
 music name: Each music expression has a name.  For example, a note
-leads to a @internalsref{NoteEvent}, and @code{\simultaneous} leads to
-a @internalsref{SimultaneousMusic}.  A list of all expressions
-available is in the Program reference manual, under
-@internalsref{Music expressions}.
+leads to a @rinternals{NoteEvent}, and @code{\simultaneous} leads to
+a @rinternals{SimultaneousMusic}.  A list of all expressions
+available is in the Internals Reference manual, under
+@rinternals{Music expressions}.
 
 @item
 @q{type} or interface: Each music name has several @q{types} or
 interfaces, for example, a note is an @code{event}, but it is also a
 @code{note-event}, a @code{rhythmic-event}, and a
 @code{melodic-event}.  All classes of music are listed in the
-Program reference, under
-@internalsref{Music classes}.
+Internals Reference, under
+@rinternals{Music classes}.
 
 @item
 C++ object: Each music object is represented by an object of the C++
@@ -426,19 +430,19 @@ class @code{Music}.
 @end itemize
 
 The actual information of a music expression is stored in properties.
-For example, a @internalsref{NoteEvent} has @code{pitch} and
+For example, a @rinternals{NoteEvent} has @code{pitch} and
 @code{duration} properties that store the pitch and duration of that
 note.  A list of all properties available is in the internals manual,
-under @internalsref{Music properties}.
+under @rinternals{Music properties}.
 
 A compound music expression is a music object that contains other
 music objects in its properties.  A list of objects can be stored in
 the @code{elements} property of a music object, or a single @q{child}
 music object in the @code{element} object.  For example,
-@internalsref{SequentialMusic} has its children in @code{elements},
-and @internalsref{GraceMusic} has its single argument in
+@rinternals{SequentialMusic} has its children in @code{elements},
+and @rinternals{GraceMusic} has its single argument in
 @code{element}.  The body of a repeat is stored in the @code{element}
-property of @internalsref{RepeatedMusic}, and the alternatives in
+property of @rinternals{RepeatedMusic}, and the alternatives in
 @code{elements}.
 
 
@@ -450,10 +454,10 @@ This section explains how to gather the information necessary
 to create complicated music functions.
 
 @menu
-* Displaying music expressions::  
-* Music properties::            
-* Doubling a note with slurs (example)::  
-* Adding articulation to notes (example)::  
+* Displaying music expressions::
+* Music properties::
+* Doubling a note with slurs (example)::
+* Adding articulation to notes (example)::
 @end menu
 
 
@@ -462,7 +466,6 @@ to create complicated music functions.
 
 @cindex internal storage
 @funindex \displayMusic
-@funindex \displayLilyMusic
 
 When writing a music function it is often instructive to inspect how
 a music expression is stored internally.  This can be done with the
@@ -575,6 +578,8 @@ of the @code{NoteEvent} object,
 
 The note pitch can be changed by setting this 'pitch property,
 
+@funindex \displayLilyMusic
+
 @example
 #(set! (ly:music-property (first (ly:music-property someNote 'elements))
                           'pitch)
@@ -589,7 +594,7 @@ d'
 @subsection Doubling a note with slurs (example)
 
 Suppose we want to create a function which translates
-input like @samp{a} into @samp{a( a)}.  We begin
+input like @code{a} into @code{a( a)}.  We begin
 by examining the internal representation of the music
 we want to end up with.
 
@@ -796,7 +801,7 @@ Here, what we want to set (the @q{place}) is the @q{elements} property of
 (the @code{'elements}, @code{'duration}, @code{'pitch}, etc, that we
 see in the @code{\displayMusic} output above).  The new value is the
 former elements property, with an extra item: the
-@code{MarcatoEvent} expression, which we copy from the
+@code{ArticulationEvent} expression, which we copy from the
 @code{\displayMusic} output,
 
 @example
@@ -810,7 +815,7 @@ original list.  This is what we
 want: the same list as before, plus the new @code{ArticulationEvent}
 expression.  The order inside the elements property is not important here.
 
-Finally, once we have added the @code{MarcatoEvent} to its elements
+Finally, once we have added the marcato articulation to its @code{elements}
 property, we can return @code{result-event-chord}, hence the last line of
 the function.
 
@@ -847,6 +852,7 @@ Stencil object given a number of arguments.
 * Markup construction in Scheme::  
 * How markups work internally::  
 * New markup command definition::  
+* New markup list command definition::  
 @end menu
 
 
@@ -859,14 +865,14 @@ The @code{markup} macro builds markup expressions in Scheme while
 providing a LilyPond-like syntax.  For example,
 @example
 (markup #:column (#:line (#:bold #:italic "hello" #:raise 0.4 "world")
-                  #:bigger #:line ("foo" "bar" "baz")))
+                  #:larger #:line ("foo" "bar" "baz")))
 @end example
 
 @noindent
 is equivalent to:
 @example
 \markup \column @{ \line @{ \bold \italic "hello" \raise #0.4 "world" @}
-                  \bigger \line @{ foo bar baz @} @}
+                  \larger \line @{ foo bar baz @} @}
 @end example
 
 @noindent
@@ -881,7 +887,7 @@ LilyPond markup syntax and Scheme markup syntax.
         @code{(markup markup1 markup2 ... )}
 @item @code{\command} @tab @code{#:command}
 @item @code{\variable} @tab @code{variable}
-@item @code{\center-align @{ ... @}} @tab @code{#:center-align ( ... )}
+@item @code{\center-column @{ ... @}} @tab @code{#:center-column ( ... )}
 @item @code{string} @tab @code{"string"}
 @item @code{#scheme-arg} @tab @code{scheme-arg}
 @end multitable
@@ -894,7 +900,7 @@ useful when defining new markup commands (see
 @ref{New markup command definition}).
 
 
-@refbugs
+@knownissues
 
 The markup-list argument of commands such as @code{#:line},
 @code{#:center}, and @code{#:column} cannot be a variable or
@@ -1111,9 +1117,106 @@ to the @code{interpret-markup} function, with the @code{layout} and
 
 Note: there is now an internal command @code{\smallCaps} which can
 be used to set text in small caps.  See
-@ref{Overview of text markup commands}, for details.
+@ref{Text markup commands}, for details.
+
+@knownissues
+
+Currently, the available combinations of arguments (after the standard
+@var{layout} and @var{props} arguments) to a markup command defined with
+@code{define-markup-command} are limited as follows.
+
+@table @asis
+@item (no argument)
+@itemx @var{list}
+@itemx @var{markup}
+@itemx @var{markup markup}
+@itemx @var{scm}
+@itemx @var{scm markup}
+@itemx @var{scm scm}
+@itemx @var{scm scm markup}
+@itemx @var{scm scm markup markup}
+@itemx @var{scm markup markup}
+@itemx @var{scm scm scm}
+@end table
+
+@noindent
+In the above table, @var{scm} represents native Scheme data types like
+@q{number} or @q{string}.
+
+As an example, it is not possible to use a markup command @code{foo} with
+four arguments defined as
+
+@example
+#(define-markup-command (foo layout props
+                         num1    str1    num2    str2)
+                        (number? string? number? string?)
+  ...)
+@end example
+
+@noindent
+If you apply it as, say,
+
+@example
+\markup \foo #1 #"bar" #2 #"baz"
+@end example
+
+@cindex Scheme signature
+@cindex signature, Scheme
+@noindent
+@command{lilypond} complains that it cannot parse @code{foo} due to its
+unknown Scheme signature.
+
+
+@node New markup list command definition
+@subsection New markup list command definition
+Markup list commands are defined with the
+@code{define-markup-list-command} Scheme macro, which is similar to the
+@code{define-markup-command} macro described in
+@ref{New markup command definition}, except that where the latter returns
+a single stencil, the former returns a list stencils.
 
+In the following example, a @code{\paragraph} markup list command is
+defined, which returns a list of justified lines, the first one being
+indented.  The indent width is taken from the @code{props} argument.
+@example
+#(define-markup-list-command (paragraph layout props args) (markup-list?)
+   (let ((indent (chain-assoc-get 'par-indent props 2)))
+     (interpret-markup-list layout props 
+       (make-justified-lines-markup-list (cons (make-hspace-markup indent)
+                                               args)))))
+@end example
 
+Besides the usual @code{layout} and @code{props} arguments, the
+@code{paragraph} markup list command takes a markup list argument, named
+@code{args}.  The predicate for markup lists is @code{markup-list?}.
+
+First, the function gets the indent width, a property here named
+@code{par-indent}, from the property list @code{props} If the property
+is not found, the default value is @code{2}.  Then, a list of justified
+lines is made using the @code{make-justified-lines-markup-list}
+function, which is related to the @code{\justified-lines}
+built-in markup list command.  An horizontal space is added at the
+beginning using the @code{make-hspace-markup} function.  Finally, the
+markup list is interpreted using the @code{interpret-markup-list}
+function.
+
+This new markup list command can be used as follows:
+@example
+\markuplines @{
+  \paragraph @{
+    The art of music typography is called \italic @{(plate) engraving.@}
+    The term derives from the traditional process of music printing.
+    Just a few decades ago, sheet music was made by cutting and stamping
+    the music into a zinc or pewter plate in mirror image.
+  @}
+  \override-lines #'(par-indent . 4) \paragraph @{
+    The plate would be inked, the depressions caused by the cutting
+    and stamping would hold ink.  An image was formed by pressing paper
+    to the plate.  The stamping and cutting was completely done by
+    hand.
+  @}
+@}
+@end example
 
 @node Contexts for programmers
 @section Contexts for programmers
@@ -1168,7 +1271,7 @@ where @var{proc} is a Scheme function, taking three arguments.
 When interpreted, the function @var{proc} is called for every layout
 object found in the context @var{context}, with the following
 arguments:
-@itemize @bullet
+@itemize
 @item the layout object itself,
 @item the context where the layout object was created, and
 @item the context where @code{\applyOutput} is processed.
@@ -1178,8 +1281,8 @@ arguments:
 In addition, the cause of the layout object, i.e., the music
 expression or object that was responsible for creating it, is in the
 object property @code{cause}.  For example, for a note head, this is a
-@internalsref{NoteHead} event, and for a @internalsref{Stem} object,
-this is a @internalsref{NoteHead} object.
+@rinternals{NoteHead} event, and for a @rinternals{Stem} object,
+this is a @rinternals{NoteHead} object.
 
 Here is a function to use for @code{\applyOutput}; it blanks
 note-heads on the center-line:
@@ -1248,8 +1351,8 @@ can be inserted with a grob closure.  Here is a setting from
 @noindent
 In this example, both @code{ly:self-alignment-interface::x-aligned-on-self} and
 @code{ly:self-alignment-interface::centered-on-x-parent} are called
-with the grob as argument. The results are added with the @code{+}
-function. To ensure that this addition is properly executed, the whole
+with the grob as argument.  The results are added with the @code{+}
+function.  To ensure that this addition is properly executed, the whole
 thing is enclosed in @code{ly:make-simple-closure}.
 
 In fact, using a single procedure as property value is equivalent to
@@ -1262,3 +1365,145 @@ In fact, using a single procedure as property value is equivalent to
 The inner @code{ly:make-simple-closure} supplies the grob as argument
 to @var{proc}, the outer ensures that result of the function is
 returned, rather than the @code{simple-closure} object.
+
+
+@node Using Scheme code instead of \tweak
+@section 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
+@code{^} and @code{_}.
+
+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
+@code{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, @code{m} itself.
+
+
+
+@node Difficult tweaks
+@section Difficult tweaks
+
+There are a few classes of difficult adjustments.
+
+@itemize
+
+
+@item
+One type of difficult adjustment is the appearance of spanner objects,
+such as slur and tie.  Initially, only one of these objects is created,
+and they can be adjusted with the normal mechanism.  However, in some
+cases the spanners cross line breaks.  If this happens, these objects
+are cloned.  A separate object is created for every system that it is
+in.  These are clones of the original object and inherit all
+properties, including @code{\override}s.
+
+
+In other words, an @code{\override} always affects all pieces of a
+broken spanner.  To change only one part of a spanner at a line break,
+it is necessary to hook into the formatting process.  The
+@code{after-line-breaking} callback contains the Scheme procedure that
+is called after the line breaks have been determined, and layout
+objects have been split over different systems.
+
+In the following example, we define a procedure
+@code{my-callback}.  This procedure
+
+@itemize
+@item
+determines if we have been split across line breaks
+@item
+if yes, retrieves all the split objects
+@item
+checks if we are the last of the split objects
+@item
+if yes, it sets @code{extra-offset}.
+@end itemize
+
+This procedure is installed into @rinternals{Tie}, so the last part
+of the broken tie is translated up.
+
+@lilypond[quote,verbatim,ragged-right]
+#(define (my-callback grob)
+  (let* (
+         ; have we been split?
+         (orig (ly:grob-original grob))
+
+         ; if yes, get the split pieces (our siblings)
+         (siblings (if (ly:grob? orig)
+                     (ly:spanner-broken-into orig) '() )))
+
+   (if (and (>= (length siblings) 2)
+             (eq? (car (last-pair siblings)) grob))
+     (ly:grob-set-property! grob 'extra-offset '(-2 . 5)))))
+
+\relative c'' {
+  \override Tie #'after-line-breaking =
+  #my-callback
+  c1 ~ \break c2 ~ c
+}
+@end lilypond
+
+@noindent
+When applying this trick, the new @code{after-line-breaking} callback
+should also call the old one @code{after-line-breaking}, if there is
+one.  For example, if using this with @code{Hairpin},
+@code{ly:hairpin::after-line-breaking} should also be called.
+
+
+@item Some objects cannot be changed with @code{\override} for
+technical reasons.  Examples of those are @code{NonMusicalPaperColumn}
+and @code{PaperColumn}.  They can be changed with the
+@code{\overrideProperty} function, which works similar to @code{\once
+\override}, but uses a different syntax.
+
+@example
+\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
+
+
+
+
+