From Andreas Henne, Support for GL3 core profile in osgText

git-svn-id: http://svn.openscenegraph.org/osg/OpenSceneGraph/trunk@14717 16af8721-9629-0410-8352-f15c8da7e697

include/osgText/Glyph

@@ -30,6 +30,15 @@
 
 #include <OpenThreads/Mutex>
 
+// GL_ALPHA is deprecated in GL3/GL4 core profile, use GL_RED and a shader in this case. See osgText example.
+#if defined(OSG_GL3_AVAILABLE) && !defined(OSG_GL2_AVAILABLE) && !defined(OSG_GL1_AVAILABLE)
+#define OSGTEXT_GLYPH_FORMAT GL_RED
+#define OSGTEXT_GLYPH_INTERNALFORMAT GL_R8
+#else
+#define OSGTEXT_GLYPH_FORMAT GL_ALPHA
+#define OSGTEXT_GLYPH_INTERNALFORMAT GL_ALPHA
+#endif
+
 namespace osgText {
 
 class Font;