Function to display the rhythmic location of a grob (issue 197690044 by address@hidden)

[david . nalesnik]

Reviewers: ,

Message:
Please review.  Thanks!

Description:
Function to display the rhythmic location of a grob

A convenient way to return the musical position of a grob within
a score will be very helpful in debugging, among other uses.

This patch creates a function ly:grob-rhythmic-location which
returns location as a list with the following structure:

(global-timestep (measure-number . measure-position))

Please review this at https://codereview.appspot.com/197690044/

Affected files (+33, -0 lines):
  M lily/grob-scheme.cc


Index: lily/grob-scheme.cc
diff --git a/lily/grob-scheme.cc b/lily/grob-scheme.cc
index  
238a0af7518189024210bda07cc9ee70aa515c40..1a1692962967208915492d9b39ce3b9a6ef506b7  
100644
--- a/lily/grob-scheme.cc
+++ b/lily/grob-scheme.cc
@@ -21,9 +21,12 @@
 #include "font-interface.hh"
 #include "grob-array.hh"
 #include "item.hh"
+#include "moment.hh"
 #include "output-def.hh"
+#include "paper-column.hh"
 #include "paper-score.hh"
 #include "simple-closure.hh"
+#include "spanner.hh"
 #include "system.hh"
 #include "unpure-pure-container.hh"
 #include "warn.hh"              // error ()
@@ -482,3 +485,33 @@ LY_DEFINE  
(ly_grob_get_vertical_axis_group_index, "ly:grob-get-vertical-axis-gro

   return scm_from_int (Grob::get_vertical_axis_group_index (gr));
 }
+
+LY_DEFINE (ly_grob_rhythmic_location, "ly:grob-rhythmic-location",
+           1, 0, 0, (SCM g),
+           "Return the rhythmic position of grob @var{g} as a list."
+           "  The @code{car} of the list is the global timestep, a"
+           " moment.  The @code{cadr} is a pair consisting of the"
+           " measure number and the position (moment) within"
+           " the measure.")
+{
+  LY_ASSERT_SMOB (Grob, g, 1);
+  Grob *me = Grob::unsmob (g);
+
+  Paper_column *col = 0;
+
+  if (Spanner *sp = dynamic_cast<Spanner *>(me))
+    {
+      if (Item *left_bound = sp->get_bound (LEFT))
+        col = left_bound->get_column ();
+    }
+  else if (Item *it = dynamic_cast<Item *>(me))
+    col = it->get_column ();
+
+  if (!col) return 0;
+
+  Moment when = Paper_column::when_mom (col);
+
+  SCM rhythmic_location = col->get_property ("rhythmic-location");
+
+  return scm_list_2 (when.smobbed_copy (), rhythmic_location);
+}