Re: Make \time work with \tweak and \footnote (issue 149170044 by address@hidden)

[dak]

Reviewers: Dan Eble,

Message:
On 2014/09/30 03:50:30, Dan Eble wrote:
> \compoundMeter should create a TimeSignatureEvent too.

[Slaps forehead]

> I managed to do it by
> incorporating \time into the definition of \compoundMeter, but perhaps
you have
> a better idea.

I'll take a look.

Description:
Make \time work with \tweak and \footnote

The way this is done is to let a TimeSignatureMusic expression expand to
produce a TimeSignatureEvent that can be listened to.  The
Time_signature_engraver _does_ listen to this event and uses it to set
the origin for TimeSignature grobs created in the same time step.
Another effect is that any warnings associated with a TimeSignature grob
will be able to point to a source location in case that the respective
change of timing parameters can be traced to TimeSignatureMusic in a
context below the context of the Time_signature_engraver creating the
TimeSignature.

Since events that can be listened to create a Bottom context implicitly,
this causes a difference for cases like

\score { { \time 3/4 \skip 2. r2. } }

Previously, Staff (and Voice) contexts were only created _after_ the
\skip completed (the timing parameters are set in the Timing context,
equal to Score by default), making the time signature appear only in
measure 2.  Now the implicit creation of a Staff (and thus a
Time_signature_engraver) in the course of creating a Bottom context (in
this case a Voice) makes the time signature appear right away.

If one uses a separate non-printing context for containing timing info,
one has to make sure that any implicitly created Bottom context is
non-printing as well.

Please review this at https://codereview.appspot.com/149170044/

Affected files (+24, -5 lines):
  M lily/time-signature-engraver.cc
  M scm/define-event-classes.scm
  M scm/define-music-callbacks.scm
  M scm/define-music-types.scm


Index: lily/time-signature-engraver.cc
diff --git a/lily/time-signature-engraver.cc  
b/lily/time-signature-engraver.cc
index  
8461a01058251f67425e2cb1bd16e335a02bc053..8c444e57471d86cd13ecfc1ed5d7d1063b789e3e  
100644
--- a/lily/time-signature-engraver.cc
+++ b/lily/time-signature-engraver.cc
@@ -22,9 +22,12 @@
 #include "item.hh"
 #include "international.hh"
 #include "misc.hh"
+#include "stream-event.hh"
 #include "time-signature.hh"
 #include "warn.hh"

+#include "translator.icc"
+
 /**
    generate time_signatures.
 */
@@ -32,6 +35,7 @@ class Time_signature_engraver : public Engraver
 {
   Item *time_signature_;
   SCM last_time_fraction_;
+  SCM time_cause_;

 protected:
   virtual void derived_mark () const;
@@ -39,26 +43,33 @@ protected:
   void process_music ();
 public:
   TRANSLATOR_DECLARATIONS (Time_signature_engraver);
+  DECLARE_TRANSLATOR_LISTENER (time_signature);
 };

 void
 Time_signature_engraver::derived_mark () const
 {
   scm_gc_mark (last_time_fraction_);
+  scm_gc_mark (time_cause_);
 }

 Time_signature_engraver::Time_signature_engraver ()
 {
   time_signature_ = 0;
+  time_cause_ = SCM_EOL;
   last_time_fraction_ = SCM_BOOL_F;
 }

+IMPLEMENT_TRANSLATOR_LISTENER (Time_signature_engraver, time_signature);
+void
+Time_signature_engraver::listen_time_signature (Stream_event *ev)
+{
+  time_cause_ = ev->self_scm ();
+}
+
 void
 Time_signature_engraver::process_music ()
 {
-  /*
-    not rigorously safe, since the value might get GC'd and
-    reallocated in the same spot */
   SCM fr = get_property ("timeSignatureFraction");
   if (!time_signature_
       && last_time_fraction_ != fr
@@ -77,7 +88,7 @@ Time_signature_engraver::process_music ()
                        den));
         }

-      time_signature_ = make_item ("TimeSignature", SCM_EOL);
+      time_signature_ = make_item ("TimeSignature", time_cause_);
       time_signature_->set_property ("fraction", fr);

       if (last_time_fraction_ == SCM_BOOL_F)
@@ -92,6 +103,7 @@ void
 Time_signature_engraver::stop_translation_timestep ()
 {
   time_signature_ = 0;
+  time_cause_ = SCM_EOL;
 }

 #include "translator.icc"
Index: scm/define-event-classes.scm
diff --git a/scm/define-event-classes.scm b/scm/define-event-classes.scm
index  
ac6f215ae2280c16a7b92a4be90ff0fc42a37c39..b56894508122c37b573711818b614194a6af85cd  
100644
--- a/scm/define-event-classes.scm
+++ b/scm/define-event-classes.scm
@@ -38,6 +38,7 @@
                     laissez-vibrer-event mark-event  
multi-measure-text-event
                     note-grouping-event pes-or-flexa-event repeat-tie-event
                     spacing-section-event layout-instruction-event
+                    time-signature-event
                     completize-extender-event break-span-event  
alternative-event))

     (layout-instruction-event . (apply-output-event))
Index: scm/define-music-callbacks.scm
diff --git a/scm/define-music-callbacks.scm b/scm/define-music-callbacks.scm
index  
e9fe53eb1b0a253e85d1af3b1d05d20ce767fae0..a6441d1e21798e58296d17fcbff0d376a0bb0ac9  
100644
--- a/scm/define-music-callbacks.scm
+++ b/scm/define-music-callbacks.scm
@@ -126,4 +126,5 @@ to be used by the sequential-iterator"
                  (ly:context-set-property!
                   context 'measureLength new-measure-length))))
             'Timing)
-           'Score))))
+           'Score)
+          (make-music 'TimeSignatureEvent music))))
Index: scm/define-music-types.scm
diff --git a/scm/define-music-types.scm b/scm/define-music-types.scm
index  
8d0464bf4c9009f2c86955ea5f9a7d4520ca3582..359e10eac1f6a4e382f9044aa5d77c88c9988738  
100644
--- a/scm/define-music-types.scm
+++ b/scm/define-music-types.scm
@@ -666,6 +666,11 @@ Syntax: @code{\\times @var{fraction} @var{music}},  
e.g.,
         (types . (general-music time-signature-music))
         ))

+    (TimeSignatureEvent
+     . ((description . "An event created when setting a new time  
signature")
+        (types . (general-music event time-signature-event))
+        ))
+
     (TransposedMusic
      . ((description . "Music that has been transposed.")
         (iterator-ctor . ,ly:music-wrapper-iterator::constructor)