Give \displayLilyMusic and \displayMusic optional port arguments.

diff --git a/Documentation/extending/scheme-tutorial.itely b/Documentation/extending/scheme-tutorial.itely
index ef6c435e49274eb39524bb7fb843a198c489c902..7951cbe7907390d560c773c1b6b2e906e890d2a1 100644 (file)
--- a/Documentation/extending/scheme-tutorial.itely
+++ b/Documentation/extending/scheme-tutorial.itely
@@ -1039,23 +1039,30 @@ will display
 
 By default, LilyPond will print these messages to the console along
 with all the other messages.  To split up these messages and save
-the results of @code{\display@{STUFF@}}, redirect the output to
-a file.
+the results of @code{\display@{STUFF@}}, you can specify an optional
+output port to use:
 
 @example
-lilypond file.ly >display.txt
+@{
+  \displayMusic #(open-output-file "display.txt") @{ c'4\f @}
+@}
 @end example
 
-With a combined bit of Lilypond and Scheme magick, you can actually
-let Lilypond direct just this output to a file of its own:
-
+This will overwrite a previous output file whenever it is called; if you
+need to write more than one expression, you would use a variable for
+your port and reuse it:
 @example
 @{
-  $(with-output-to-file "display.txt"
-      (lambda () #@{ \displayMusic @{ c'4\f @} #@}))
+  port = #(open-output-file "display.txt")
+  \displayMusic \port @{ c'4\f @}
+  \displayMusic \port @{ d'4 @}
+  #(close-output-port port)
 @}
 @end example
 
+Guile's manual describes ports in detail.  Closing the port is actually
+only necessary if you need to read the file before Lilypond finishes; in
+the first example, we did not bother to do so.
 
 A bit of reformatting makes the above information easier to read:
 

diff --git a/ly/music-functions-init.ly b/ly/music-functions-init.ly
index 038f2ef6ac89b9a42ac19a9df7d7c3179aaa98fb..90cae893c674cf27b5678749a63d8ac9f5462661 100644 (file)
--- a/ly/music-functions-init.ly
+++ b/ly/music-functions-init.ly
@@ -273,18 +273,23 @@ in a CueVoice oriented by @var{dir}.")
 
 
 displayLilyMusic =
-#(define-music-function (parser location music) (ly:music?)
+#(define-music-function (parser location port music) ((port?) ly:music?)
    (_i "Display the LilyPond input representation of @var{music}
-to the console.")
-   (newline)
-   (display-lily-music music parser)
+to @var{port}, defaulting to the console.")
+   (if (not port)
+       (set! port (current-output-port)))
+   (newline port)
+   (display-lily-music music parser port)
    music)
 
 displayMusic =
-#(define-music-function (parser location music) (ly:music?)
-   (_i "Display the internal representation of @var{music} to the console.")
-   (newline)
-   (display-scheme-music music)
+#(define-music-function (parser location port music) ((port?) ly:music?)
+   (_i "Display the internal representation of @var{music} to
+@var{port}, default to the console.")
+   (if (not port)
+       (set! port (current-output-port)))
+   (newline port)
+   (display-scheme-music music port)
    music)
 
 

diff --git a/scm/music-functions.scm b/scm/music-functions.scm
index 250defcdd2f98bdaa09761b16a98eb1d62cd2802..6beff26744ce724ed2777da1201c6ee9a605a137 100644 (file)
--- a/scm/music-functions.scm
+++ b/scm/music-functions.scm
@@ -98,24 +98,23 @@ First it recurses over the children, then the function is applied to
       music
       (make-music 'Music)))      ;must return music.
 
-(define-public (display-music music)
+(define*-public (display-music music #:optional (port (current-output-port)))
   "Display music, not done with @code{music-map} for clarity of
 presentation."
-
-  (display music)
-  (display ": { ")
+  (display music port)
+  (display ": { " port)
   (let ((es (ly:music-property music 'elements))
        (e (ly:music-property music 'element)))
-    (display (ly:music-mutable-properties music))
+    (display (ly:music-mutable-properties music) port)
     (if (pair? es)
-       (begin (display "\nElements: {\n")
-              (map display-music es)
-              (display "}\n")))
+       (begin (display "\nElements: {\n" port)
+              (for-each (lambda (m) (display-music m port)) es)
+              (display "}\n" port)))
     (if (ly:music? e)
        (begin
-         (display "\nChild:")
-         (display-music e))))
-  (display " }\n")
+         (display "\nChild:" port)
+         (display-music e port))))
+  (display " }\n" port)
   music)
 
 ;;;
@@ -211,7 +210,7 @@ which often can be read back in order to generate an equivalent expression.
 Returns `obj'.
 "
   (pretty-print (music->make-music obj) port)
-  (newline)
+  (newline port)
   obj)
 
 ;;;
@@ -220,14 +219,15 @@ Returns `obj'.
 (use-modules (srfi srfi-39)
              (scm display-lily))
 
-(define*-public (display-lily-music expr parser #:key force-duration)
+(define*-public (display-lily-music expr parser #:optional (port (current-output-port))
+                                   #:key force-duration)
   "Display the music expression using LilyPond syntax"
   (memoize-clef-names supported-clefs)
   (parameterize ((*indent* 0)
                 (*previous-duration* (ly:make-duration 2))
                 (*force-duration* force-duration))
-    (display (music->lily-string expr parser))
-    (newline)))
+    (display (music->lily-string expr parser) port)
+    (newline port)))
 
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