throw if we encounter a font file which lacks any referencable names (freetype family_name and style_name) making it basically invalid

CHANGELOG

@@ -14,6 +14,8 @@ For a complete change history, see the SVN log.
 Mapnik Trunk
 ------------
 
+- Throw an error during registration for fonts which Freetype2 does not report a family or style name (r2985).
+
 - Fixed quoting syntax for "table"."attribute" in PostGIS plugin (previously if table aliases were used quoting like "table.attribute" would cause query failure) (r2979).
 
 - Added the ability to control the PostGIS feature id by suppling a key_field to reference and integer attribute name (r2979).

src/font_engine_freetype.cpp

@@ -27,6 +27,7 @@
 // boost
 #include <boost/algorithm/string.hpp>
 #include <boost/filesystem.hpp>
+#include <sstream>
 
 namespace mapnik
 {
@@ -78,10 +79,22 @@ bool freetype_engine::register_font(std::string const& file_name)
         FT_Done_FreeType(library);
         return false;
     }
-    std::string name = std::string(face->family_name) + " " + std::string(face->style_name);
-    name2file_.insert(std::make_pair(name,file_name));
-    FT_Done_Face(face );   
-    FT_Done_FreeType(library);
+    // some fonts can lack names, skip them
+    // http://www.freetype.org/freetype2/docs/reference/ft2-base_interface.html#FT_FaceRec
+    if (face->family_name && face->style_name) {
+        std::string name = std::string(face->family_name) + " " + std::string(face->style_name);
+        name2file_.insert(std::make_pair(name,file_name));
+        FT_Done_Face(face);
+        FT_Done_FreeType(library);
+        return true;
+    } else {
+        FT_Done_Face(face);
+        FT_Done_FreeType(library);
+        std::ostringstream s;
+        s << "Error: unable to load invalid font file which lacks identifiable family and style name: '"
+          << file_name << "'";
+        throw std::runtime_error(s.str());
+    }
     return true;
 }