Add display method for \tweak (fixes issue 1733) (issue4645077)

[n . puttock]

Reviewers: ,

Message:
This patch allows \tweak to be displayed properly when using
\displayLilyMusic.

* scm/display-lily.scm (music->lily-string):

  process 'tweaks via new function music->lily-string

This should read

  process 'tweaks via new function tweaks->lily-string

Description:
Add display method for \tweak.

* input/regression/display-lily-tests.ly:

  add tests for \tweak

* scm/define-music-display-methods.scm

  (scheme-expr->lily-string): don't funnel booleans through pretty-print
  (EventChord): treat simple_element with 'tweaks list as
note_chord_element
                to preserve < > around tweaked note

* scm/display-lily.scm (music->lily-string):

  process 'tweaks via new function music->lily-string

Please review this at http://codereview.appspot.com/4645077/

Affected files:
  M input/regression/display-lily-tests.ly
  M scm/define-music-display-methods.scm
  M scm/display-lily.scm


Index: input/regression/display-lily-tests.ly
diff --git a/input/regression/display-lily-tests.ly  
b/input/regression/display-lily-tests.ly
index  
08a13bdc780cfa991a8f7ee5cffd52d35f03b1d8..008c4f20f2f13bec83ff45091b2224be572a3f06  
100644
--- a/input/regression/display-lily-tests.ly
+++ b/input/regression/display-lily-tests.ly
@@ -241,6 +241,12 @@ stderr of this run."
 %% \ottava
 \test "" ##[ \ottava #1 #] % OttavaMusic

+%% \tweak
+\test "" ##[ < \tweak #'duration-log #2 c > #]
+\test "" ##[ < c \tweak #'transparent ##t e > #]
+\test "" ##[ < \tweak #'color #'(1.0 0.0 0.0) \tweak #'duration-log #2 c >  
#]
+\test "" ##[ c-\tweak #'font-size #3 -> #]
+
 %% end test.

 #(read-hash-extend #\[ #f) %{ ] %}
Index: scm/define-music-display-methods.scm
diff --git a/scm/define-music-display-methods.scm  
b/scm/define-music-display-methods.scm
index  
3ecfce5aaf1cdffce6a962576f3454bb8d996011..c0041ba2a98344efe4fdef5fe097a9e0f832e0cb  
100644
--- a/scm/define-music-display-methods.scm
+++ b/scm/define-music-display-methods.scm
@@ -16,7 +16,8 @@
 ;;;
 (define (scheme-expr->lily-string scm-arg)
   (cond ((or (number? scm-arg)
-            (string? scm-arg))
+             (string? scm-arg)
+             (boolean? scm-arg))
         (format #f "~s" scm-arg))
        ((or (symbol? scm-arg)
             (list? scm-arg))
@@ -466,7 +467,9 @@ Otherwise, return #f."
                 ;; as a note_chord_element to prevent spurious output, e.g.,
                 ;; \displayLilyMusic < c-1\4 >8 -> c-1\48
                 (null? (filter post-event?
-                               (ly:music-property (car simple-elements) 
'articulations))))
+                               (ly:music-property (car simple-elements) 
'articulations)))
+                ;; same for simple_element with \tweak
+                (null? (ly:music-property (car simple-elements) 'tweaks)))
 	    ;; simple_element : note | figure | rest | mmrest | lyric_element |  
skip
            (let* ((simple-element (car simple-elements))
                   (duration (ly:music-property simple-element 'duration))
Index: scm/display-lily.scm
diff --git a/scm/display-lily.scm b/scm/display-lily.scm
index  
6fc933499df5c0ace9bb92ef2fda02b70d4683d9..302259fa23eda7d78d9704dc87f0c77fa6edbb15  
100644
--- a/scm/display-lily.scm
+++ b/scm/display-lily.scm
@@ -79,6 +79,15 @@ display method will be called."
                 (format #f "~a\\tag #'~a" (if post-event? "-" "") tag))
               (ly:music-property expr 'tags))))

+(define* (tweaks->lily-string expr #:optional (post-event? #f))
+  (format #f "~{~a ~}"
+          (map (lambda (tweak)
+                 (format #f "~a\\tweak #'~a #~a"
+                         (if post-event? "-" "")
+                         (car tweak)
+                         (scheme-expr->lily-string (cdr tweak))))
+               (ly:music-property expr 'tweaks))))
+
 (define-public (music->lily-string expr parser)
   "Print @var{expr}, a music expression, in LilyPond syntax."
   (if (ly:music? expr)
@@ -90,8 +99,9 @@ display method will be called."
                                              (proc expr parser))
                                            procs))))
        (if result-string
-           (format #f "~a~a"
-                   (tag->lily-string expr (post-event? expr))
+           (format #f "~a~a~a"
+                    (tag->lily-string expr (post-event? expr))
+                    (tweaks->lily-string expr (post-event? expr))
                    result-string)
            (format #f "%{ Print method not implemented for music type ~a %}"
                    music-type)))