From Marco Jez, addition of glw extension checking under Windows, and tweaks to

BlendEquation and RenderStage to correct the extensions being tested.

src/osg/BlendEquation.cpp

@@ -108,8 +108,8 @@ void BlendEquation::Extensions::setupGLExtenions(unsigned int contextID)
     _isBlendEquationSupported = isGLExtensionSupported(contextID,"GL_EXT_blend_equation") ||
                              strncmp((const char*)glGetString(GL_VERSION),"1.2",3)>=0;
     
-    _isSGIXMinMaxSupported = isGLExtensionSupported(contextID, "SGIX_blend_alpha_minmax");
-    _isLogicOpSupported = isGLExtensionSupported(contextID, "EXT_blend_logic_op");
+    _isSGIXMinMaxSupported = isGLExtensionSupported(contextID, "GL_SGIX_blend_alpha_minmax");
+    _isLogicOpSupported = isGLExtensionSupported(contextID, "GL_EXT_blend_logic_op");
 
     _glBlendEquation = getGLExtensionFuncPtr("glBlendEquation", "glBlendEquationEXT");
 }

src/osg/GLExtensions.cpp

@@ -24,6 +24,10 @@
 #include <vector>
 #include <set>
 
+#if defined(WIN32)
+#include <windows.h>
+#endif
+
 bool osg::isGLExtensionSupported(unsigned int contextID, const char *extension)
 {
     typedef std::set<std::string>  ExtensionSet;
@@ -56,6 +60,44 @@ bool osg::isGLExtensionSupported(unsigned int contextID, const char *extension)
             startOfWord = endOfWord+1;
         }
         if (*startOfWord!=0) extensionSet.insert(std::string(startOfWord));
+
+#if defined(WIN32)
+
+        // add WGL extensions to the list
+
+        typedef const char* WINAPI WGLGETEXTENSIONSSTRINGARB(HDC);
+        WGLGETEXTENSIONSSTRINGARB* wglGetExtensionsStringARB = 
+            (WGLGETEXTENSIONSSTRINGARB*)getGLExtensionFuncPtr("wglGetExtensionsStringARB");
+        
+        typedef const char* WINAPI WGLGETEXTENSIONSSTRINGEXT();
+        WGLGETEXTENSIONSSTRINGEXT* wglGetExtensionsStringEXT = 
+            (WGLGETEXTENSIONSSTRINGEXT*)getGLExtensionFuncPtr("wglGetExtensionsStringEXT");
+        
+        const char* wglextensions = 0;
+        
+        if (wglGetExtensionsStringARB)
+        {
+            HDC dc = wglGetCurrentDC();
+            wglextensions = wglGetExtensionsStringARB(dc);
+        }
+        else if (wglGetExtensionsStringEXT)
+        {
+            wglextensions = wglGetExtensionsStringEXT();
+        }
+
+        if (wglextensions)
+        {    
+            const char* startOfWord = wglextensions;
+            const char* endOfWord;
+            while ((endOfWord = strchr(startOfWord, ' ')))
+            {
+                extensionSet.insert(std::string(startOfWord, endOfWord));
+                startOfWord = endOfWord+1;
+            }
+            if (*startOfWord != 0) extensionSet.insert(std::string(startOfWord));
+        }
+
+#endif
         
         osg::notify(INFO)<<"OpenGL extensions supported by installed OpenGL drivers are:"<<std::endl;
         for(ExtensionSet::iterator itr=extensionSet.begin();

src/osgUtil/RenderStage.cpp

@@ -373,7 +373,7 @@ void RenderStage::runCameraSetUp(osg::State& state)
     
     // check whether PBuffer-RTT is supported or not
     if (renderTargetImplemntation==osg::CameraNode::PIXEL_BUFFER_RTT && 
-        !osg::isGLExtensionSupported(state.getContextID(), "ARB_render_texture"))
+        !osg::isGLExtensionSupported(state.getContextID(), "WGL_ARB_render_texture"))
     {    
         if (renderTargetImplemntation<renderTargetFallback)
             renderTargetImplemntation = renderTargetFallback;