From e9697859bdcd943bdc12ddf76d9ea249c8c8eead Mon Sep 17 00:00:00 2001
From: Robert Osfield <robert@openscenegraph.com>
Date: Mon, 9 Sep 2013 13:33:13 +0000
Subject: [PATCH] From Colin McDonald, "Add test for GL_EXT_framebuffer_object
 extension : osg uses osg::FBOExtensions to check if Frame Buffer Objects are
 available.  But this just checks if the fbo functions can be called. It
 doesn't check if the OpenGL renderer supports fbos.  For indirect rendering
 on linux the client side capability may be different from the display server,
 which can lead to mipmapped textures failing to render.  I've added a fbo
 extension check. "

---
 src/osg/FrameBufferObject.cpp | 3 ++-
 src/osg/Texture.cpp           | 7 ++++---
 2 files changed, 6 insertions(+), 4 deletions(-)

diff --git a/src/osg/FrameBufferObject.cpp b/src/osg/FrameBufferObject.cpp
index ec570d14e..ee06df812 100644
--- a/src/osg/FrameBufferObject.cpp
+++ b/src/osg/FrameBufferObject.cpp
@@ -105,7 +105,8 @@ FBOExtensions::FBOExtensions(unsigned int contextID)
 #if !defined(OSG_GLES1_AVAILABLE) && !defined(OSG_GLES2_AVAILABLE)
     _supported = _supported &&
         glFramebufferTexture1D != 0 &&
-        glFramebufferTexture3D != 0;
+        glFramebufferTexture3D != 0 &&
+        isGLExtensionOrVersionSupported(contextID, "GL_EXT_framebuffer_object",3.0f);
 #endif
 
     LOAD_FBO_EXT(glBlitFramebuffer);
diff --git a/src/osg/Texture.cpp b/src/osg/Texture.cpp
index 89eea7f53..3569d16f3 100644
--- a/src/osg/Texture.cpp
+++ b/src/osg/Texture.cpp
@@ -2351,7 +2351,7 @@ bool Texture::isHardwareMipmapGenerationEnabled(const State& state) const
 
         const FBOExtensions* fbo_ext = FBOExtensions::instance(contextID,true);
 
-        if (fbo_ext->glGenerateMipmap)
+        if (fbo_ext->isSupported() && fbo_ext->glGenerateMipmap)
         {
             return true;
         }
@@ -2368,7 +2368,8 @@ Texture::GenerateMipmapMode Texture::mipmapBeforeTexImage(const State& state, bo
         return GENERATE_MIPMAP;
 #else
 
-        bool useGenerateMipMap = FBOExtensions::instance(state.getContextID(), true)->glGenerateMipmap!=0;
+        FBOExtensions* fbo_ext = FBOExtensions::instance(state.getContextID(),true);
+        bool useGenerateMipMap = fbo_ext->isSupported() && fbo_ext->glGenerateMipmap;
 
         if (useGenerateMipMap)
         {
@@ -2440,7 +2441,7 @@ void Texture::generateMipmap(State& state) const
     osg::FBOExtensions* fbo_ext = osg::FBOExtensions::instance(state.getContextID(), true);
 
     // check if the function is supported
-    if (fbo_ext->glGenerateMipmap)
+    if (fbo_ext->isSupported() && fbo_ext->glGenerateMipmap)
     {
         textureObject->bind();
         fbo_ext->glGenerateMipmap(textureObject->target());