From c1d6a2fd92fb2e68335c03940684c27ac3ec6680 Mon Sep 17 00:00:00 2001
From: Paul Davis <paul@linuxaudiosystems.com>
Date: Thu, 17 Sep 2015 17:16:05 -0400
Subject: [PATCH] add string_compose argument specializations so that empty
 std::string and empty C strings are handled as intended

---
 libs/pbd/pbd/compose.h | 40 ++++++++++++++++++++++++++++++++++++++++
 1 file changed, 40 insertions(+)

diff --git a/libs/pbd/pbd/compose.h b/libs/pbd/pbd/compose.h
index cb4182699f..b3b6ea21d1 100644
--- a/libs/pbd/pbd/compose.h
+++ b/libs/pbd/pbd/compose.h
@@ -54,6 +54,10 @@ namespace StringPrivate
     template <typename T>
     Composition &arg(const T &obj);
 
+    // specialization to catch strings (C++ and C)
+    Composition &arg(const std::string &str);
+    Composition &arg(char const * const cstr);
+
     // compose and return string
     std::string str() const;
 
@@ -138,6 +142,42 @@ namespace StringPrivate
     return *this;
   }
 
+  inline Composition &Composition::arg(const std::string &str)
+  {
+	  /* specialization to ensure that empty strings show up
+	   * in the output
+	   */
+	  for (specification_map::const_iterator i = specs.lower_bound(arg_no),
+		       end = specs.upper_bound(arg_no); i != end; ++i) {
+		  output_list::iterator pos = i->second;
+		  ++pos;
+
+		  output.insert(pos, str);
+	  }
+
+	  ++arg_no;
+
+	  return *this;
+  }
+
+  inline Composition &Composition::arg(char const * const cstr)
+  {
+	  /* specialization to ensure that empty C strings show up
+	   * in the output
+	   */
+	  for (specification_map::const_iterator i = specs.lower_bound(arg_no),
+		       end = specs.upper_bound(arg_no); i != end; ++i) {
+		  output_list::iterator pos = i->second;
+		  ++pos;
+
+		  output.insert(pos, std::string (cstr));
+	  }
+
+	  ++arg_no;
+	  
+	  return *this;
+  }
+
   inline Composition::Composition(std::string fmt)
     : arg_no(1)
   {