OpenSceneGraph/include/osg/Drawable

/* -*-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.
*/

#ifndef OSG_DRAWABLE
#define OSG_DRAWABLE 1

#include <osg/BoundingBox>
#include <osg/NodeVisitor>
#include <osg/Shape>
#include <osg/BufferObject>
#include <osg/PrimitiveSet>


#ifndef GL_NV_occlusion_query

    #define GL_OCCLUSION_TEST_HP                0x8165
    #define GL_OCCLUSION_TEST_RESULT_HP         0x8166
    #define GL_PIXEL_COUNTER_BITS_NV            0x8864
    #define GL_CURRENT_OCCLUSION_QUERY_ID_NV    0x8865
    #define GL_PIXEL_COUNT_NV                   0x8866
    #define GL_PIXEL_COUNT_AVAILABLE_NV         0x8867

#endif

#ifndef GL_ARB_occlusion_query

    #define GL_SAMPLES_PASSED_ARB               0x8914
    #define GL_QUERY_COUNTER_BITS_ARB           0x8864
    #define GL_CURRENT_QUERY_ARB                0x8865
    #define GL_QUERY_RESULT_ARB                 0x8866
    #define GL_QUERY_RESULT_AVAILABLE_ARB       0x8867

#endif


namespace osg {


class Vec2f;
class Vec3f;
class Vec4f;
class UByte4;
class Geometry;

// this is defined to alter the way display lists are compiled inside the
// the draw method, it has been found that the NVidia drivers fail completely
// to optimize COMPILE_AND_EXECUTE in fact make it go slower than for no display
// lists, but optimize a separate COMPILE very well?!  Define it as default
// the use of a separate COMPILE, then glCallList rather than use COMPILE_AND_EXECUTE.

#define USE_SEPARATE_COMPILE_AND_EXECUTE

/** Pure virtual base class for drawable geometry. In OSG, everything that can
 *  be rendered is implemented as a class derived from \c Drawable. The
 *  \c Drawable class contains no drawing primitives, since these are provided
 *  by subclasses such as \c osg::Geometry.
 *  <p>Notice that a \c Drawable is not a \c Node, and therefore it cannot be
 *  directly added to a scene graph. Instead, <tt>Drawable</tt>s are attached to
 *  <tt>Geode</tt>s, which are scene graph nodes.
 *  <p>The OpenGL state that must be used when rendering a \c Drawable is
 *  represented by a \c StateSet. Since a \c Drawable has a reference
 *  (\c osg::ref_ptr) to a \c StateSet, <tt>StateSet</tt>s can be shared between
 *  different <tt>Drawable</tt>s. In fact, sharing <tt>StateSet</tt>s is a good
 *  way to improve performance, since this allows OSG to reduce the number of
 *  expensive changes in the OpenGL state.
 *  <p>Finally, <tt>Drawable</tt>s can also be shared between different
 *  <tt>Geode</tt>s, so that the same geometry (loaded to memory just once) can
 *  be used in different parts of the scene graph.
*/
class SG_EXPORT Drawable : public Object
{
    public:

        static unsigned int s_numberDrawablesReusedLastInLastFrame;
        static unsigned int s_numberNewDrawablesInLastFrame;
        static unsigned int s_numberDeletedDrawablesInLastFrame;

        Drawable();

        /** Copy constructor using CopyOp to manage deep vs shallow copy.*/
        Drawable(const Drawable& drawable,const CopyOp& copyop=CopyOp::SHALLOW_COPY);

        virtual bool isSameKindAs(const Object* obj) const { return dynamic_cast<const Drawable*>(obj)!=NULL; }
        virtual const char* libraryName() const { return "osg"; }
        virtual const char* className() const { return "Drawable"; }

        /** Convert 'this' into a Geometry pointer if Drawable is a Geometry, otherwise return 0.
          * Equivalent to dynamic_cast<Geometry*>(this).*/
        virtual Geometry* asGeometry() { return 0; }
        /** Convert 'const this' into a const Geometry pointer if Drawable is a Geometry, otherwise return 0.
          * Equivalent to dynamic_cast<const Geometry*>(this).*/
        virtual const Geometry* asGeometry() const { return 0; }


        /** A vector of osg::Node pointers which is used to store the parent(s) of drawable.*/
        typedef std::vector<Node*> ParentList;

        /** Get the parent list of drawable. */
        inline const ParentList& getParents() const { return _parents; }

        /** Get the a copy of parent list of node. A copy is returned to
          * prevent modification of the parent list.*/
        inline ParentList getParents() { return _parents; }

        /** Get a single parent of Drawable.
          * @param i index of the parent to get.
          * @return the parent i.
          */
        inline Node* getParent(unsigned int i)  { return _parents[i]; }
        /** Get a single const parent of Drawable.
          * @param i index of the parent to get.
          * @return the parent i.
          */
        inline const Node* getParent(unsigned int i) const  { return _parents[i]; }

        /**
         * Get the number of parents of node.
         * @return the number of parents of this node.
         */
        inline unsigned int getNumParents() const { return _parents.size(); }



        /** Set the StateSet attached to the Drawable.
            Previously attached StateSet are automatically unreferenced on
            assignment of a new drawstate.*/
        inline void setStateSet(StateSet *state) { _stateset = state; }

        /** Get the attached StateSet.*/
        inline StateSet* getStateSet() { return _stateset.get();}

        /** Get the attached const StateSet.*/
        inline const StateSet* getStateSet() const { return _stateset.get();}

        /** Get the attached const StateSet,
          * if one is not already attached create one,
          * attach it to the drawable and return a pointer to it.*/
        StateSet* getOrCreateStateSet();


        /** Dirty the bounding box, forcing a computeBound() on the next call
          * to getBound(). Should be called in the internal geometry of the Drawable
          * is modified.*/
        void dirtyBound();

        /** get bounding box of geoset.
          * Note, now made virtual to make it possible to implement user-drawn
          * objects albeit somewhat crudely, to be improved later.
          */
        inline const BoundingBox& getBound() const
        {
            if( !_bbox_computed)
                computeBound();
            return _bbox;
        }


        /** Set the Shape of the \c Drawable. The shape can be used to
         *  speed up collision detection or as a guide for procedural
         *  geometry generation.
         * @see osg::Shape.
        */
        inline void setShape(Shape* shape) { _shape = shape; }

        /** Get the Shape of the Drawable.*/
        inline Shape* getShape() { return _shape.get(); }

        /** Get the const Shape of the const Drawable.*/
        inline const Shape* getShape() const { return _shape.get(); }



        /** Set the drawable so that it can or cannot be used in conjunction with OpenGL
          * display lists.  When set to true, calls to Drawable::setUseDisplayList,
          * whereas when set to false, no display lists can be created and calls
          * to setUseDisplayList are ignored, and a warning is produced.  The latter
          * is typically used to guard against the switching on of display lists
          * on objects with dynamic internal data such as continuous Level of Detail
          * algorithms.*/
        void setSupportsDisplayList(bool flag);

        /** Get whether display lists are supported for this drawable instance.*/
        inline bool getSupportsDisplayList() const { return _supportsDisplayList; }


        /** When set to true, force the draw method to use OpenGL Display List for rendering.
            If false, rendering directly.  If the display list has not been compiled
            already, the next call to draw will automatically create the display list.*/
        void setUseDisplayList(bool flag);

        /** Return whether OpenGL display lists are being used for rendering.*/
        inline bool getUseDisplayList() const { return _useDisplayList; }

        /** When set to true, ignore the setUseDisplayList() settings, and hints to the drawImplementation 
            method to use OpenGL vertex buffer objects for rendering.*/
        void setUseVertexBufferObjects(bool flag);

        /** Return whether OpenGL vertex buffer objects should be used when supported by OpenGL driver.*/
        inline bool getUseVertexBufferObjects() const { return _useVertexBufferObjects; }


        /** Force a recompile on next draw() of any OpenGL display list associated with this geoset.*/
        void dirtyDisplayList();


        /** Return the estimated size of GLObjects (display lists/vertex buffer objects) that are associated with this drawable.
          * This size is used a hint for reuse of deleteed display lists/vertex buffer objects. */
        virtual unsigned int getGLObjectSizeHint() const { return 0; }



        /** Draw OpenGL primitives.
          * If the \c Drawable has \c _useDisplayList set to \c true, then use
          * an OpenGL display list, automatically compiling one if required.
          * Otherwise, call \c drawImplementation().
          * @note This method should \e not be overridden in subclasses, as it
          *       manages the optional display list (notice this is not even
          *       \c virtual). Subclasses should override
          *       \c drawImplementation() instead.
          */
        inline void draw(State& state) const;

        /** Immediately compile this \c Drawable into an OpenGL Display List.
          * @note Operation is ignored if \c _useDisplayList is \c false.
          * @note This member function is not intended to be overridden in
          *       subclasses (notice that it is not even \c virtual).
        */
        virtual void compileGLObjects(State& state) const;

        /**
            if osg::State object is supplied: release any OpenGL display lists associated with graphics context specified
            or
            if state pointer is NULL: release all display lists for all graphics contexts */
        virtual void releaseGLObjects(State* state=0) const;

        struct UpdateCallback : public virtual osg::Object
        {
            UpdateCallback() {}

            UpdateCallback(const UpdateCallback&,const CopyOp&) {}

            META_Object(osg,UpdateCallback);

            /** do customized update code.*/
            virtual void update(osg::NodeVisitor*, osg::Drawable*) {}
        };

        /** Set the UpdateCallback which allows users to attach customize the updating of an object during the update traversal.*/
        virtual void setUpdateCallback(UpdateCallback* ac);

        /** Get the non const UpdateCallback.*/
        UpdateCallback* getUpdateCallback() { return _updateCallback.get(); }

        /** Get the const UpdateCallback.*/
        const UpdateCallback* getUpdateCallback() const { return _updateCallback.get(); }


        struct CullCallback : public virtual osg::Object
        {
            CullCallback() {}

            CullCallback(const CullCallback&,const CopyOp&) {}

            META_Object(osg,CullCallback);

            /** do customized cull code, return true if drawable should be culled.*/
            virtual bool cull(osg::NodeVisitor*, osg::Drawable*, osg::State*) const { return false; }
        };

        /** Set the CullCallback which allows users to customize the culling of Drawable during the cull traversal.*/
        virtual void setCullCallback(CullCallback* cc) { _cullCallback=cc; }

        /** Get the non const CullCallback.*/
        CullCallback* getCullCallback() { return _cullCallback.get(); }

        /** Get the const CullCallback.*/
        const CullCallback* getCullCallback() const { return _cullCallback.get(); }




        /** Callback attached to an Drawable which allows the users to customize the drawing of an exist Drawable object.
          * The draw callback is implement as a replacement to the Drawable's own drawImplementation() method, if the
          * the user intends to decorate the existing draw code then simple call the drawable->drawImplementation() from
          * with the callbacks drawImplementation() method.  This allows the users to do both pre and post callbacks
          * without fuss and can even disable the inner draw if required.*/
        struct DrawCallback : public virtual osg::Object
        {
            DrawCallback() {}

            DrawCallback(const DrawCallback&,const CopyOp&) {}

            META_Object(osg,DrawCallback);

            /** do customized draw code.*/
            virtual void drawImplementation(osg::State&,const osg::Drawable*) const {}
        };

        /** Set the DrawCallback which allows users to attach customize the drawing of existing Drawable object.*/
        virtual void setDrawCallback(DrawCallback* dc) { _drawCallback=dc; dirtyDisplayList(); }

        /** Get the non const DrawCallback.*/
        DrawCallback* getDrawCallback() { return _drawCallback.get(); }

        /** Get the const DrawCallback.*/
        const DrawCallback* getDrawCallback() const { return _drawCallback.get(); }



        /** drawImplementation(State&) is a pure virtaul method for the actual implementation of OpenGL drawing calls, such as vertex arrays and primitives, that
          * must be implemented in concrete subclasses of the Drawable base class, examples include osg::Geometry and osg::ShapeDrawable.
          * drawImplementation(State&) is called from the draw(State&) method, with the draw method handling management of OpenGL display lists,
          * and drawImplementation(State&) handling the actuall drawing itself.  
          * @param state The osg::State object that encapulates the current OpenGL state for the current graphics context. */
        virtual void drawImplementation(State& state) const = 0;


        /** Return a OpenGL display list handle a newly generated or reused from display list cache. */
        static GLuint generateDisplayList(unsigned int contextID, unsigned int sizeHint = 0);

        /** Set the minimum number of display lists to retain in the deleted display list cache. */
        static void setMinimumNumberOfDisplayListsToRetainInCache(unsigned int minimum);

        /** Get the minimum number of display lists to retain in the deleted display list cache. */
        static unsigned int getMinimumNumberOfDisplayListsToRetainInCache();

        /** Use deleteDisplayList instead of glDeleteList to allow
          * OpenGL display list to be cached until they can be deleted
          * by the OpenGL context in which they were created, specified
          * by contextID.*/
        static void deleteDisplayList(unsigned int contextID,GLuint globj, unsigned int sizeHint = 0);

        /** Flush all the cached display list which need to be deleted
          * in the OpenGL context related to contextID.*/
        static void flushAllDeletedDisplayLists(unsigned int contextID);

        /** Flush the cached display list which need to be deleted
          * in the OpenGL context related to contextID.*/
        static void flushDeletedDisplayLists(unsigned int contextID,double& availableTime);

        /** Use deleteVertexBufferObject instead of glDeleteBuffers to allow
          * OpenGL buffer objects to be cached until they can be deleted
          * by the OpenGL context in which they were created, specified
          * by contextID.*/
        static void deleteVertexBufferObject(unsigned int contextID,GLuint globj);

        /** Flush all the cached vertex buffer objects which need to be deleted
          * in the OpenGL context related to contextID.*/
        static void flushDeletedVertexBufferObjects(unsigned int contextID,double currentTime, double& availableTime);

        typedef unsigned int AttributeType;

        enum AttributeTypes
        {
            VERTICES            = 0,
            WEIGHTS             = 1,
            NORMALS             = 2,
            COLORS              = 3,
            SECONDARY_COLORS    = 4,
            FOG_COORDS          = 5,
            ATTIBUTE_6          = 6,
            ATTIBUTE_7          = 7,
            TEXTURE_COORDS      = 8,
            TEXTURE_COORDS_0    = TEXTURE_COORDS,
            TEXTURE_COORDS_1    = TEXTURE_COORDS_0+1,
            TEXTURE_COORDS_2    = TEXTURE_COORDS_0+2,
            TEXTURE_COORDS_3    = TEXTURE_COORDS_0+3,
            TEXTURE_COORDS_4    = TEXTURE_COORDS_0+4,
            TEXTURE_COORDS_5    = TEXTURE_COORDS_0+5,
            TEXTURE_COORDS_6    = TEXTURE_COORDS_0+6,
            TEXTURE_COORDS_7    = TEXTURE_COORDS_0+7
            // only eight texture coord examples provided here, but underlying code can handle any no of texure units,
            // simply co them as (TEXTURE_COORDS_0+unit).
        };

        class AttributeFunctor
        {
        public:
            virtual ~AttributeFunctor() {}

            virtual void apply(AttributeType,unsigned int,GLbyte*) {}
            virtual void apply(AttributeType,unsigned int,GLshort*) {}
            virtual void apply(AttributeType,unsigned int,GLint*) {}

            virtual void apply(AttributeType,unsigned int,GLubyte*) {}
            virtual void apply(AttributeType,unsigned int,GLushort*) {}
            virtual void apply(AttributeType,unsigned int,GLuint*) {}

            virtual void apply(AttributeType,unsigned int,float*) {}
            virtual void apply(AttributeType,unsigned int,Vec2*) {}
            virtual void apply(AttributeType,unsigned int,Vec3*) {}
            virtual void apply(AttributeType,unsigned int,Vec4*) {}
            virtual void apply(AttributeType,unsigned int,UByte4*) {}
        };


        /** Return true if the Drawable subclass supports accept(AttributeFunctor&).*/
        virtual bool supports(AttributeFunctor&) const { return false; }

        /** accept an AttributeFunctor and call its methods to tell it about the internal attributes that this Drawable has.
          * return true if functor handled by drawable,
          * return false on failure of drawable to generate functor calls.*/
        virtual void accept(AttributeFunctor&) {}


        class ConstAttributeFunctor
        {
        public:

            virtual ~ConstAttributeFunctor() {}

            virtual void apply(AttributeType,const unsigned int,const GLbyte*) {}
            virtual void apply(AttributeType,const unsigned int,const GLshort*) {}
            virtual void apply(AttributeType,const unsigned int,const GLint*) {}

            virtual void apply(AttributeType,const unsigned int,const GLubyte*) {}
            virtual void apply(AttributeType,const unsigned int,const GLushort*) {}
            virtual void apply(AttributeType,const unsigned int,const GLuint*) {}

            virtual void apply(AttributeType,const unsigned int,const float*) {}
            virtual void apply(AttributeType,const unsigned int,const Vec2*) {}
            virtual void apply(AttributeType,const unsigned int,const Vec3*) {}
            virtual void apply(AttributeType,const unsigned int,const Vec4*) {}
            virtual void apply(AttributeType,const unsigned int,const UByte4*) {}
        };

        /** Return true if the Drawable subclass supports accept(ConstAttributeFunctor&).*/
        virtual bool supports(ConstAttributeFunctor&) const { return false; }

        /** Accept an AttributeFunctor and call its methods to tell it about the internal attributes that this Drawable has.
          * return true if functor handled by drawable,
          * return false on failure of drawable to generate functor calls.*/
        virtual void accept(ConstAttributeFunctor&) const {}



        /** Return true if the Drawable subclass supports accept(PrimitiveFunctor&).*/
        virtual bool supports(PrimitiveFunctor&) const { return false; }

        /** Accept a PrimitiveFunctor and call its methods to tell it about the internal primitives that this Drawable has.
          * return true if functor handled by drawable, return false on failure of drawable to generate functor calls.
          * Note, PrimtiveFunctor only provides const access of the primitives, as primitives may be procedurally generated
          * so one cannot modify it.*/
        virtual void accept(PrimitiveFunctor&) const {}

        /** Return true if the Drawable subclass supports accept(PrimitiveIndexFunctor&).*/
        virtual bool supports(PrimitiveIndexFunctor&) const { return false; }

        /** Accept a PrimitiveIndexFunctor and call its methods to tell it about the internal primitives that this Drawable has.
          * return true if functor handled by drawable, return false on failure of drawable to generate functor calls.
          * Note, PrimtiveIndexFunctor only provide const access of the primitives, as primitives may be procedurally generated
          * so one cannot modify it.*/
        virtual void accept(PrimitiveIndexFunctor&) const {}


        /** Extensions class which encapsulates the querying of extensions and
        * associated function pointers, and provide convenience wrappers to
        * check for the extensions or use the associated functions.*/
        class SG_EXPORT Extensions : public osg::Referenced
        {
        public:
            Extensions();

            Extensions(const Extensions& rhs);

            void lowestCommonDenominator(const Extensions& rhs);

            void setupGLExtenions();

            void setVertexProgramSupported(bool flag) { _isVertexProgramSupported=flag; }
            bool isVertexProgramSupported() const { return _isVertexProgramSupported; }

            void setSecondaryColorSupported(bool flag) { _isSecondaryColorSupported=flag; }
            bool isSecondaryColorSupported() const { return _isSecondaryColorSupported; }

            void setFogCoordSupported(bool flag) { _isFogCoordSupported=flag; }
            bool isFogCoordSupported() const { return _isFogCoordSupported; }

            void setMultiTexSupported(bool flag) { _isMultiTexSupported=flag; }
            bool isMultiTexSupported() const { return _isMultiTexSupported; }

            void setOcclusionQuerySupported(bool flag) { _isOcclusionQuerySupported=flag; }
            bool isOcclusionQuerySupported() const { return _isOcclusionQuerySupported; }

            void setARBOcclusionQuerySupported(bool flag) { _isARBOcclusionQuerySupported=flag; }
            bool isARBOcclusionQuerySupported() const { return _isARBOcclusionQuerySupported; }

            void glSecondaryColor3ubv(const GLubyte* coord) const;
            void glSecondaryColor3fv(const GLfloat* coord) const;

            void glFogCoordfv(const GLfloat* coord) const;

            void glMultiTexCoord1f(GLenum target,GLfloat coord) const;
            void glMultiTexCoord2fv(GLenum target,const GLfloat* coord) const;
            void glMultiTexCoord3fv(GLenum target,const GLfloat* coord) const;
            void glMultiTexCoord4fv(GLenum target,const GLfloat* coord) const;

            void glVertexAttrib1s(unsigned int index, GLshort s) const;
            void glVertexAttrib1f(unsigned int index, GLfloat f) const;
            void glVertexAttrib2fv(unsigned int index, const GLfloat * v) const;
            void glVertexAttrib3fv(unsigned int index, const GLfloat * v) const;
            void glVertexAttrib4fv(unsigned int index, const GLfloat * v) const;
            void glVertexAttrib4ubv(unsigned int index, const GLubyte * v) const;
            void glVertexAttrib4Nubv(unsigned int index, const GLubyte * v) const;


            void glGenBuffers (GLsizei n, GLuint *buffers) const;
            void glBindBuffer (GLenum target, GLuint buffer) const;
            void glBufferData (GLenum target, GLsizeiptrARB size, const GLvoid *data, GLenum usage) const;
            void glBufferSubData (GLenum target, GLintptrARB offset, GLsizeiptrARB size, const GLvoid *data) const;
            void glDeleteBuffers (GLsizei n, const GLuint *buffers) const;
            GLboolean glIsBuffer (GLuint buffer) const;
            void glGetBufferSubData (GLenum target, GLintptrARB offset, GLsizeiptrARB size, GLvoid *data) const;
            GLvoid* glMapBuffer (GLenum target, GLenum access) const;
            GLboolean glUnmapBuffer (GLenum target) const;
            void glGetBufferParameteriv (GLenum target, GLenum pname, GLint *params) const;
            void glGetBufferPointerv (GLenum target, GLenum pname, GLvoid* *params) const;


            void glGenOcclusionQueries( GLsizei n, GLuint *ids ) const;
            void glDeleteOcclusionQueries( GLsizei n, const GLuint *ids ) const;
            GLboolean glIsOcclusionQuery( GLuint id ) const;
            void glBeginOcclusionQuery( GLuint id ) const;
            void glEndOcclusionQuery() const;
            void glGetOcclusionQueryiv( GLuint id, GLenum pname, GLint *params ) const;
            void glGetOcclusionQueryuiv( GLuint id, GLenum pname, GLuint *params ) const;

            void glGetQueryiv(GLenum target, GLenum pname, GLint *params) const;
            void glGenQueries(GLsizei n, GLuint *ids) const;
            void glBeginQuery(GLenum target, GLuint id) const;
            void glEndQuery(GLenum target) const;
            GLboolean glIsQuery(GLuint id) const;
            void glGetQueryObjectiv(GLuint id, GLenum pname, GLint *params) const;
            void glGetQueryObjectuiv(GLuint id, GLenum pname, GLuint *params) const;

        protected:

            typedef void (APIENTRY * FogCoordProc) (const GLfloat* coord);

            typedef void (APIENTRY * VertexAttrib1sProc) (unsigned int index, GLshort s);
            typedef void (APIENTRY * VertexAttrib1fProc) (unsigned int index, GLfloat f);
            typedef void (APIENTRY * VertexAttribfvProc) (unsigned int index, const GLfloat * v);
            typedef void (APIENTRY * VertexAttribubvProc) (unsigned int index, const GLubyte * v);

            typedef void (APIENTRY * SecondaryColor3ubvProc) (const GLubyte* coord);
            typedef void (APIENTRY * SecondaryColor3fvProc) (const GLfloat* coord);

            typedef void (APIENTRY * MultiTexCoord1fProc) (GLenum target,GLfloat coord);
            typedef void (APIENTRY * MultiTexCoordfvProc) (GLenum target,const GLfloat* coord);


            typedef void (APIENTRY * GenBuffersProc) (GLsizei n, GLuint *buffers);
            typedef void (APIENTRY * BindBufferProc) (GLenum target, GLuint buffer);
            typedef void (APIENTRY * BufferDataProc) (GLenum target, GLsizeiptrARB size, const GLvoid *data, GLenum usage);
            typedef void (APIENTRY * BufferSubDataProc) (GLenum target, GLintptrARB offset, GLsizeiptrARB size, const GLvoid *data);
            typedef void (APIENTRY * DeleteBuffersProc) (GLsizei n, const GLuint *buffers);
            typedef GLboolean (APIENTRY * IsBufferProc) (GLuint buffer);
            typedef void (APIENTRY * GetBufferSubDataProc) (GLenum target, GLintptrARB offset, GLsizeiptrARB size, GLvoid *data);
            typedef GLvoid* (APIENTRY * MapBufferProc) (GLenum target, GLenum access);
            typedef GLboolean (APIENTRY * UnmapBufferProc) (GLenum target);
            typedef void (APIENTRY * GetBufferParameterivProc) (GLenum target, GLenum pname, GLint *params);
            typedef void (APIENTRY * GetBufferPointervProc) (GLenum target, GLenum pname, GLvoid* *params);

            typedef void (APIENTRY * GenOcclusionQueriesProc) ( GLsizei n, GLuint *ids );
            typedef void (APIENTRY * DeleteOcclusionQueriesProc) ( GLsizei n, const GLuint *ids );
            typedef GLboolean (APIENTRY * IsOcclusionQueryProc) ( GLuint id );
            typedef void (APIENTRY * BeginOcclusionQueryProc) ( GLuint id );
            typedef void (APIENTRY * EndOcclusionQueryProc) ();
            typedef void (APIENTRY * GetOcclusionQueryivProc) ( GLuint id, GLenum pname, GLint *params );
            typedef void (APIENTRY * GetOcclusionQueryuivProc) ( GLuint id, GLenum pname, GLuint *params );

            typedef void (APIENTRY *GenQueriesProc) (GLsizei n, GLuint *ids);
            typedef void (APIENTRY *DeleteQueriesProc) (GLsizei n, const GLuint *ids);
            typedef GLboolean (APIENTRY *IsQueryProc) (GLuint id);
            typedef void (APIENTRY *BeginQueryProc) (GLenum target, GLuint id);
            typedef void (APIENTRY *EndQueryProc) (GLenum target);
            typedef void (APIENTRY *GetQueryivProc) (GLenum target, GLenum pname, GLint *params);
            typedef void (APIENTRY *GetQueryObjectivProc) (GLuint id, GLenum pname, GLint *params);
            typedef void (APIENTRY *GetQueryObjectuivProc) (GLuint id, GLenum pname, GLuint *params);

            ~Extensions() {}

            bool _isVertexProgramSupported;
            bool _isSecondaryColorSupported;
            bool _isFogCoordSupported;
            bool _isMultiTexSupported;
            bool _isOcclusionQuerySupported;
            bool _isARBOcclusionQuerySupported;

            FogCoordProc _glFogCoordfv;

            SecondaryColor3ubvProc _glSecondaryColor3ubv;
            SecondaryColor3fvProc _glSecondaryColor3fv;

            VertexAttrib1sProc _glVertexAttrib1s;
            VertexAttrib1fProc _glVertexAttrib1f;
            VertexAttribfvProc _glVertexAttrib2fv;
            VertexAttribfvProc _glVertexAttrib3fv;
            VertexAttribfvProc _glVertexAttrib4fv;
            VertexAttribubvProc _glVertexAttrib4ubv;
            VertexAttribubvProc _glVertexAttrib4Nubv;

            MultiTexCoord1fProc _glMultiTexCoord1f;
            MultiTexCoordfvProc _glMultiTexCoord2fv;
            MultiTexCoordfvProc _glMultiTexCoord3fv;
            MultiTexCoordfvProc _glMultiTexCoord4fv;

            GenBuffersProc          _glGenBuffers;
            BindBufferProc          _glBindBuffer;
            BufferDataProc          _glBufferData;
            BufferSubDataProc       _glBufferSubData;
            DeleteBuffersProc       _glDeleteBuffers;
            IsBufferProc            _glIsBuffer;
            GetBufferSubDataProc    _glGetBufferSubData;
            MapBufferProc           _glMapBuffer;
            UnmapBufferProc         _glUnmapBuffer;
            GetBufferParameterivProc _glGetBufferParameteriv;
            GetBufferPointervProc   _glGetBufferPointerv;

            GenOcclusionQueriesProc _glGenOcclusionQueries;
            DeleteOcclusionQueriesProc _glDeleteOcclusionQueries;
            IsOcclusionQueryProc _glIsOcclusionQuery;
            BeginOcclusionQueryProc _glBeginOcclusionQuery;
            EndOcclusionQueryProc _glEndOcclusionQuery;
            GetOcclusionQueryivProc _glGetOcclusionQueryiv;
            GetOcclusionQueryuivProc _glGetOcclusionQueryuiv;

            GenQueriesProc _gl_gen_queries_arb;
            DeleteQueriesProc _gl_delete_queries_arb;
            IsQueryProc _gl_is_query_arb;
            BeginQueryProc _gl_begin_query_arb;
            EndQueryProc _gl_end_query_arb;
            GetQueryivProc _gl_get_queryiv_arb;
            GetQueryObjectivProc _gl_get_query_objectiv_arb;
            GetQueryObjectuivProc  _gl_get_query_objectuiv_arb;

        };

        /** Function to call to get the extension of a specified context.
        * If the Exentsion object for that context has not yet been created  
        * and the 'createIfNotInitalized' flag been set to false then returns NULL.
        * If 'createIfNotInitalized' is true then the Extensions object is 
        * automatically created.  However, in this case the extension object is
        * only created with the graphics context associated with ContextID..*/
        static Extensions* getExtensions(unsigned int contextID,bool createIfNotInitalized);

        /** setExtensions allows users to override the extensions across graphics contexts.
        * typically used when you have different extensions supported across graphics pipes
        * but need to ensure that they all use the same low common denominator extensions.*/
        static void setExtensions(unsigned int contextID,Extensions* extensions);


    protected:

        Drawable& operator = (const Drawable&) { return *this;}

        virtual ~Drawable();

        /** Compute the bounding box of the drawable. Method must be 
            implemented by subclasses.*/
        virtual bool computeBound() const;

        /** set the bounding box .*/
        void setBound(const BoundingBox& bb) const;

        void addParent(osg::Node* node);
        void removeParent(osg::Node* node);

        ParentList _parents;
        friend class Node;
        friend class Geode;

        ref_ptr<StateSet>       _stateset;

        mutable BoundingBox     _bbox;
        mutable bool            _bbox_computed;

        ref_ptr<Shape>           _shape;

        bool                    _supportsDisplayList;
        bool                    _useDisplayList;
        bool                    _supportsVertexBufferObjects;
        bool                    _useVertexBufferObjects;

        typedef osg::buffered_value<GLuint> GLObjectList;
        mutable GLObjectList    _globjList;
        mutable GLObjectList    _vboList;

        ref_ptr<UpdateCallback> _updateCallback;
        ref_ptr<CullCallback>   _cullCallback;
        ref_ptr<DrawCallback>   _drawCallback;
};

inline void Drawable::draw(State& state) const
{
    if (_useDisplayList && !(_supportsVertexBufferObjects && _useVertexBufferObjects && state.isVertexBufferObjectSupported()))
    {
        // get the contextID (user defined ID of 0 upwards) for the
        // current OpenGL context.
        unsigned int contextID = state.getContextID();

        // get the globj for the current contextID.
        GLuint& globj = _globjList[contextID];

        // call the globj if already set otherwise compile and execute.
        if( globj != 0 )
        {
            glCallList( globj );
        }
        else if (_useDisplayList)
        {
#ifdef USE_SEPARATE_COMPILE_AND_EXECUTE
            globj = generateDisplayList(contextID, getGLObjectSizeHint());
            glNewList( globj, GL_COMPILE );
            if (_drawCallback.valid())
                _drawCallback->drawImplementation(state,this);
            else
                drawImplementation(state);
            glEndList();

            glCallList( globj);
#else
            globj = generateDisplayList(contextID, getGLObjectSizeHint());
            glNewList( globj, GL_COMPILE_AND_EXECUTE );
            if (_drawCallback.valid())
                _drawCallback->drawImplementation(state,this);
            else
                drawImplementation(state);
            glEndList();
#endif
        }

        return;

    }

    // draw object as nature intended..
    if (_drawCallback.valid())
        _drawCallback->drawImplementation(state,this);
    else
        drawImplementation(state);
};


}

#endif