From Alberto Farre, added support for GL_EXT_blend_color, GL_ARB_multisample,

GL_NV_multisample_filter_hint extension in the form of osg::BlendColor and
osg::Multisample state attribute classes.

src/osg/BlendColor.cpp

@@ -0,0 +1,105 @@
+/* -*-c++-*- OpenSceneGraph - Copyright (C) 1998-2003 Robert Osfield 
+ *
+ * This library is open source and may be redistributed and/or modified under  
+ * the terms of the OpenSceneGraph Public License (OSGPL) version 0.0 or 
+ * (at your option) any later version.  The full license is in LICENSE file
+ * included with this distribution, and on the openscenegraph.org website.
+ * 
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the 
+ * OpenSceneGraph Public License for more details.
+*/
+#include <osg/BlendColor>
+#include <osg/GLExtensions>
+#include <osg/State>
+#include <osg/Notify>
+
+using namespace osg;
+
+
+BlendColor::BlendColor() :
+            _constantColor(0.0f,0.0f,0.0f,0.0f)
+{
+}
+
+BlendColor::~BlendColor()
+{
+}
+
+void BlendColor::apply(State& state) const
+{
+    // get the contextID (user defined ID of 0 upwards) for the 
+    // current OpenGL context.
+    const unsigned int contextID = state.getContextID();
+    
+    const Extensions* extensions = getExtensions(contextID,true);
+                                        
+    if (!extensions->isBlendColorSupported())
+    {
+        notify(WARN)<<"Warning: BlendColor::apply(..) failed, BlendColor is not support by OpenGL driver."<<std::endl;
+        return;
+    }
+
+    extensions->glBlendColor(_constantColor[0], _constantColor[1],
+                             _constantColor[2], _constantColor[3]);
+}
+
+
+
+
+
+typedef buffered_value< ref_ptr<BlendColor::Extensions> > BufferedExtensions;
+static BufferedExtensions s_extensions;
+
+BlendColor::Extensions* BlendColor::getExtensions(unsigned int contextID,bool createIfNotInitalized)
+{
+    if (!s_extensions[contextID] && createIfNotInitalized) s_extensions[contextID] = new Extensions;
+    return s_extensions[contextID].get();
+}
+
+void BlendColor::setExtensions(unsigned int contextID,Extensions* extensions)
+{
+    s_extensions[contextID] = extensions;
+}
+
+
+BlendColor::Extensions::Extensions()
+{
+    setupGLExtenions();
+}
+
+BlendColor::Extensions::Extensions(const Extensions& rhs):
+    Referenced()
+{
+    _isBlendColorSupported = rhs._isBlendColorSupported;
+}
+
+void BlendColor::Extensions::lowestCommonDenominator(const Extensions& rhs)
+{
+    if (!rhs._isBlendColorSupported)  _isBlendColorSupported = false;
+    if (!rhs._glBlendColor)           _glBlendColor = 0;
+}
+
+void BlendColor::Extensions::setupGLExtenions()
+{
+    _isBlendColorSupported = isGLExtensionSupported("GL_EXT_blend_color") ||
+                             strncmp((const char*)glGetString(GL_VERSION),"1.2",3)>=0;
+
+    _glBlendColor = getGLExtensionFuncPtr("glBlendColor", "glBlendColorEXT");
+}
+
+void BlendColor::Extensions::glBlendColor(GLclampf red , GLclampf green , GLclampf blue , GLclampf alpha) const
+{
+    if (_glBlendColor)
+    {
+        typedef void (APIENTRY * GLBlendColorProc) (GLclampf red, GLclampf green, GLclampf blue, GLclampf alpha);
+        ((GLBlendColorProc)_glBlendColor)(red, green, blue, alpha);
+    }
+    else
+    {
+        notify(WARN)<<"Error: glBlendColor not supported by OpenGL driver"<<std::endl;
+    }
+}
+
+