Introduce ly_scm2utf8_string, and use it for printing text (issue 577440043 by address@hidden)

[hanwenn]

Reviewers: dak,

Message:
I think this may have lacked sf.net issue. Please review.

Description:
Introduce ly_scm2utf8_string, and use it for printing text

Before, Text_interface::interpret_string used ly_scm2string, which
runs scm_to_locale_stringn to get at the string. The default locale is
"C", so all Unicode chars are then converted to "?".

Please review this at https://codereview.appspot.com/577440043/

Affected files (+20, -1 lines):
  M lily/include/lily-guile.hh
  M lily/lily-guile.cc
  M lily/text-interface.cc


Index: lily/include/lily-guile.hh
diff --git a/lily/include/lily-guile.hh b/lily/include/lily-guile.hh
index 
ab14e8541e4f6a39bd9d87a0bc262c0b86805af1..ccbebcadf976bd2da40a14e2e0d88edc715ac0a4
 100644
--- a/lily/include/lily-guile.hh
+++ b/lily/include/lily-guile.hh
@@ -57,6 +57,7 @@ std::string gulp_file_to_string (const std::string &fn, bool 
must_exist, int siz
 
 SCM ly_string2scm (std::string const &s);
 std::string ly_scm2string (SCM s);
+std::string ly_scm2utf8_string (SCM);
 std::string ly_symbol2string (SCM);
 std::string robust_symbol2string (SCM, const std::string&);
 Rational ly_scm2rational (SCM);
Index: lily/lily-guile.cc
diff --git a/lily/lily-guile.cc b/lily/lily-guile.cc
index 
7f084806e928aebf1a1add8e0dbe9f41a95fcf82..84e2e69672f2590acdbf3938fa739edcacecda7b
 100644
--- a/lily/lily-guile.cc
+++ b/lily/lily-guile.cc
@@ -119,6 +119,24 @@ extern "C" {
 /*
   STRINGS
  */
+string
+ly_scm2utf8_string (SCM str)
+{
+#if GUILEV2
+  assert (scm_is_string (str));
+  size_t len = 0;
+  char *bytes = scm_to_utf8_stringn (str, &len);
+
+  // It would be nice to stick 'bytes' directly into string.
+  string result(bytes, len);
+
+  free(bytes);
+  return result;
+#else
+  return ly_scm2string(str);
+#endif
+}
+
 string
 ly_scm2string (SCM str)
 {
Index: lily/text-interface.cc
diff --git a/lily/text-interface.cc b/lily/text-interface.cc
index 
1f62e9b287290439d45375e717b03196656ac763..9d8de13778966b169771c7762a186adc6cb61e00
 100644
--- a/lily/text-interface.cc
+++ b/lily/text-interface.cc
@@ -78,7 +78,7 @@ Text_interface::interpret_string (SCM layout_smob,
   LY_ASSERT_SMOB (Output_def, layout_smob, 1);
   LY_ASSERT_TYPE (scm_is_string, markup, 3);
 
-  string str = ly_scm2string (markup);
+  string str = ly_scm2utf8_string (markup);
   Output_def *layout = unsmob<Output_def> (layout_smob);
   Font_metric *fm = select_encoded_font (layout, props);