From Wang Lam,"The changes allow users of OpenSceneGraph to call a new function

readFontStream() to load fonts from a std::istream, rather than from the
local filesystem by name.  Such a call may be used, for example, if the
user has a font fetched over a network, or a font available in memory
without a correspondng filename.

The changes implement the new function by following the corresponding code
for readFontFile().  readFontStream() reads a stream into memory, and
holds that memory for FreeType.

As a basic test, I mangled the osgtext example to use
readFontStream(std::ifstream("font")) in lieu of a readFontFile call, and
the modified example ran completely."

include/osgText/Font

@@ -15,6 +15,7 @@
 #define OSGTEXT_FONT 1
 
 #include <string>
+#include <istream>
 
 #include <osg/Vec2>
 #include <osg/Image>
@@ -57,6 +58,10 @@ enum KerningType
   * the file will be searched again in the OS specific directories.
   */
 extern OSGTEXT_EXPORT Font* readFontFile(const std::string& filename);
+
+/** read a font from specified stream.*/
+extern OSGTEXT_EXPORT Font* readFontStream(std::istream& stream);
+
 extern OSGTEXT_EXPORT std::string findFontFile(const std::string& str);
 
 /** Pure virtual base class for fonts.