Merge branch 'master' of ssh+git://git.sv.gnu.org/srv/git/lilypond

[lilypond.git] / Documentation / user / scheme-tutorial.itely

diff --git a/Documentation/user/scheme-tutorial.itely b/Documentation/user/scheme-tutorial.itely
index 5eba9a146516b5022e760650f75cfe4b5dbe54f0..757951b5fb0c093542b11dbce3972662d0e2461d 100644 (file)
--- a/Documentation/user/scheme-tutorial.itely
+++ b/Documentation/user/scheme-tutorial.itely
@@ -151,14 +151,14 @@ is put into the @code{thickness} variable of a @code{Stem}
 object.  @code{thickness} is measured relative to the thickness of
 staff lines, so these stem lines will be @code{2.6} times the
 width of staff lines.  This makes stems almost twice as thick as their
-normal size. To distinguish between variables defined in input files (like
+normal size.  To distinguish between variables defined in input files (like
 @code{twentyFour} in the example above) and variables of internal
-objects, we will call the latter ``properties'' and the former
-``identifiers.''  So, the stem object has a @code{thickness} property,
-while @code{twentyFour} is an identifier.
+objects, we will call the latter @q{properties} and the former
+@q{variables.}  So, the stem object has a @code{thickness} property,
+while @code{twentyFour} is an variable.
 
-@cindex properties vs. identifiers
-@cindex identifiers vs. properties
+@cindex properties vs. variables
+@cindex variables vs. properties
 
 Two-dimensional offsets (X and Y coordinates) as well as object sizes
 (intervals with a left and right point) are entered as @code{pairs}.  A
@@ -208,4 +208,79 @@ respectively,
 @end example
 
 
+@menu
+* Tweaking with Scheme::        
+@end menu
+
+@node Tweaking with Scheme
+@appendixsec Tweaking with Scheme
+
+We have seen how LilyPond output can be heavily modified using
+commands like
+@code{\override TextScript #'extra-offset = ( 1 . -1)}.  But
+we have even more power if we use Scheme.  For a full explanation
+of this, see the @ref{Scheme tutorial}, and
+@ruser{Interfaces for programmers}.
+
+We can use Scheme to simply @code{\override} commands,
+
+TODO Find a simple example
+@c This isn't a valid example with skylining
+@c It works fine without padText  -td
+
+@ignore
+@lilypond[quote,verbatim,ragged-right]
+padText = #(define-music-function (parser location padding) (number?)
+#{
+  \once \override TextScript #'padding = #$padding
+#})
+
+\relative c''' {
+  c4^"piu mosso" b a b
+  \padText #1.8
+  c4^"piu mosso" d e f
+  \padText #2.6
+  c4^"piu mosso" fis a g
+}
+@end lilypond
+@end ignore
+
+We can use it to create new commands:
+
+@c Check this is a valid example with skylining
+@c It is - 'padding still works
+
+@lilypond[quote,verbatim,ragged-right]
+tempoMark = #(define-music-function (parser location padding marktext)
+                                    (number? string?)
+#{
+  \once \override Score . RehearsalMark #'padding = $padding
+  \once \override Score . RehearsalMark #'extra-spacing-width = #'(+inf.0 . -inf.0)
+  \mark \markup { \bold $marktext }
+#})
+
+\relative c'' {
+  c2 e
+  \tempoMark #3.0 #"Allegro"
+  g c
+}
+@end lilypond
+
+Even music expressions can be passed in:
+
+@lilypond[quote,verbatim,ragged-right]
+pattern = #(define-music-function (parser location x y) (ly:music? ly:music?)
+#{
+  $x e8 a b $y b a e
+#})
+
+\relative c''{
+  \pattern c8 c8\f
+  \pattern {d16 dis} { ais16-> b\p }
+}
+@end lilypond
+
+
+
+