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/State>
#include <osg/NodeVisitor>
#include <osg/Shape>
#include <osg/buffered_value>

namespace osg {

class Vec2;
class Vec3;
class Vec4;
class UByte4;
class Geometry;

#ifndef GL_ARB_vertex_buffer_object

    // for compatibility with gl.h headers that don't support VBO,
    #if defined(_WIN64)
        typedef __int64 GLintptrARB;
        typedef __int64 GLsizeiptrARB;
    #elif defined(__ia64__) || defined(__x86_64__)
        typedef long int GLintptrARB;
        typedef long int GLsizeiptrARB;
    #else
        typedef int GLintptrARB;
        typedef int GLsizeiptrARB;
    #endif
    
    #define GL_ARRAY_BUFFER_ARB               0x8892
    #define GL_ELEMENT_ARRAY_BUFFER_ARB       0x8893
    #define GL_ARRAY_BUFFER_BINDING_ARB       0x8894
    #define GL_ELEMENT_ARRAY_BUFFER_BINDING_ARB 0x8895
    #define GL_VERTEX_ARRAY_BUFFER_BINDING_ARB 0x8896
    #define GL_NORMAL_ARRAY_BUFFER_BINDING_ARB 0x8897
    #define GL_COLOR_ARRAY_BUFFER_BINDING_ARB 0x8898
    #define GL_INDEX_ARRAY_BUFFER_BINDING_ARB 0x8899
    #define GL_TEXTURE_COORD_ARRAY_BUFFER_BINDING_ARB 0x889A
    #define GL_EDGE_FLAG_ARRAY_BUFFER_BINDING_ARB 0x889B
    #define GL_SECONDARY_COLOR_ARRAY_BUFFER_BINDING_ARB 0x889C
    #define GL_FOG_COORDINATE_ARRAY_BUFFER_BINDING_ARB 0x889D
    #define GL_WEIGHT_ARRAY_BUFFER_BINDING_ARB 0x889E
    #define GL_VERTEX_ATTRIB_ARRAY_BUFFER_BINDING_ARB 0x889F
    #define GL_STREAM_DRAW_ARB                0x88E0
    #define GL_STREAM_READ_ARB                0x88E1
    #define GL_STREAM_COPY_ARB                0x88E2
    #define GL_STATIC_DRAW_ARB                0x88E4
    #define GL_STATIC_READ_ARB                0x88E5
    #define GL_STATIC_COPY_ARB                0x88E6
    #define GL_DYNAMIC_DRAW_ARB               0x88E8
    #define GL_DYNAMIC_READ_ARB               0x88E9
    #define GL_DYNAMIC_COPY_ARB               0x88EA
    #define GL_READ_ONLY_ARB                  0x88B8
    #define GL_WRITE_ONLY_ARB                 0x88B9
    #define GL_READ_WRITE_ARB                 0x88BA
    #define GL_BUFFER_SIZE_ARB                0x8764
    #define GL_BUFFER_USAGE_ARB               0x8765
    #define GL_BUFFER_ACCESS_ARB              0x88BB
    #define GL_BUFFER_MAPPED_ARB              0x88BC
    #define GL_BUFFER_MAP_POINTER_ARB         0x88BD

#endif


// this is define 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 sperate COMPILE, then glCallList rather than use COMPILE_AND_EXECUTE.

#define USE_SEPARATE_COMPILE_AND_EXECUTE

/** Pure virtual base class for drawable Geometry.  Contains no drawing primitives
    directly, these are provided by subclasses such as osg::Geometry. State attributes 
    for a Drawable are maintained in StateSet which the Drawable maintains
    a referenced counted pointer to.  Both Drawable's and StateSet's can 
    be shared for optimal memory usage and graphics performance.
*/
class SG_EXPORT Drawable : public Object
{
    public:

        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 attach 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 so what crudely, to be improved later.
          */
        inline const BoundingBox& getBound() const
        {
            if( !_bbox_computed)
                computeBound();
            return _bbox;
        }


    	/** Set the Shape of the drawable. The shape can be used to
	  * speed up collision detection or as a guide for produral
	  * geometry generation - see osg::ProduralGeometry.*/
    	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 to it can or cannot be used in conjunction with OpenGL
          * display lists.  With 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 later
          * 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 already
            compile 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 drawImplemention 
            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();



        /** draw OpenGL primitives. 
          * If the drawable has _useDisplayList set to true then use an OpenGL display
          * list, automatically compiling one if required.
          * Otherwise call drawImplementation().
          * Note, draw method should *not* be overridden in subclasses as it 
          * manages the optional display list.
          */
        inline void draw(State& state) const;
        
        /** Immediately compile this drawable into an OpenGL Display List.
            Note I, operation is ignored if _useDisplayList to false.
            Note II, compile is not intended to be overridden in subclasses.*/
        virtual void compile(State& state) const;


        struct UpdateCallback : public virtual osg::Referenced
        {
                /** do customized app code.*/
                virtual void update(osg::NodeVisitor *visitor, osg::Drawable* drawable) = 0;
        };
        
        /** Set the UpdateCallback which allows users to attach customize the undating of an object during the app traversal.*/
        void setUpdateCallback(UpdateCallback* ac);
        
        /** Get the non const UpdateCallback.*/
        UpdateCallback* getUpdateCallback() { return _updateCallback.get(); }


        struct CullCallback : public virtual osg::Referenced
        {
                /** do customized cull code.*/
                virtual bool cull(osg::NodeVisitor *visitor, osg::Drawable* drawable, osg::State *state=NULL) const = 0;
        };

        /** Set the CullCallback which allows users to attach customize the culling of Drawable during the cull traversal.*/
        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 exist 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 diable the inner draw in required.*/
        struct DrawCallback : public virtual osg::Referenced
        {
            /** do customized draw code.*/
            virtual void drawImplementation(State& state,const osg::Drawable* drawable) const = 0;
        };

        /** Set the DrawCallback which allows users to attach customize the drawing of existing Drawable object.*/
        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(); }



        /** draw directly ignoring an OpenGL display list which could be attached.
          * This is the internal draw method which does the drawing itself,
          * and is the method to override when deriving from Drawable.
          */
        virtual void drawImplementation(State& state) const = 0;



        /** use deleteDisplayList instead of glDeleteList to allow
          * OpenGL display list to 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);
        
        /** flush all the cached display list which need to be deleted
          * in the OpenGL context related to contextID.*/
        static void flushDeletedDisplayLists(unsigned int contextID,double currentTime, double& availableTime);

        /** use deleteVertexBufferObject instead of glDeleteList to allow
          * OpenGL buffer objects to 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 interal 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 interal 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 {}


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

            virtual void setVertexArray(unsigned int count,const Vec2* vertices) = 0;
            virtual void setVertexArray(unsigned int count,const Vec3* vertices) = 0;
            virtual void setVertexArray(unsigned int count,const Vec4* vertices) = 0;
            
            virtual void drawArrays(GLenum mode,GLint first,GLsizei count) = 0;
            virtual void drawElements(GLenum mode,GLsizei count,const GLubyte* indices) = 0;
            virtual void drawElements(GLenum mode,GLsizei count,const GLushort* indices) = 0;
            virtual void drawElements(GLenum mode,GLsizei count,const GLuint* indices) = 0;
            
            virtual void begin(GLenum mode) = 0;
            virtual void vertex(const Vec2& vert) = 0;
            virtual void vertex(const Vec3& vert) = 0;
            virtual void vertex(const Vec4& vert) = 0;
            virtual void vertex(float x,float y) = 0;
            virtual void vertex(float x,float y,float z) = 0;
            virtual void vertex(float x,float y,float z,float w) = 0;
            virtual void end() = 0;
            
        };
        
        /** return true if the Drawable subclass supports accept(PrimitiveFunctor&).*/
        virtual bool supports(PrimitiveFunctor&) const { return false; }

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


        /** Extensions class which encapsulates the querring of extensions and
        * associated function pointers, and provide convinience 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 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;

	    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;

        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 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 );

	    ~Extensions() {}

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

            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;

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

        /** Function to call to get the extension of a specified context.
        * If the Exentsion object for that context has not yet been created then 
        * 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 
        * only be 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<DrawCallback>   _drawCallback;
        ref_ptr<CullCallback>   _cullCallback;
        

};

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 = glGenLists( 1 );
            glNewList( globj, GL_COMPILE );
            if (_drawCallback.valid())
                _drawCallback->drawImplementation(state,this);
            else 
                drawImplementation(state);
            glEndList();
            
            glCallList( globj);
#else
            globj = glGenLists( 1 );
            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