Multisample

/* -*-c++-*- OpenSceneGraph - Copyright (C) 1998-2006 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_MULTISAMPLE
#define OSG_MULTISAMPLE 1


#include <osg/GL>
#include <osg/StateAttribute>
#include <osg/ref_ptr>


#ifndef GL_ARB_multisample
#define GL_MULTISAMPLE_ARB                0x809D
#define GL_SAMPLE_ALPHA_TO_COVERAGE_ARB   0x809E
#define GL_SAMPLE_ALPHA_TO_ONE_ARB        0x809F
#define GL_SAMPLE_COVERAGE_ARB            0x80A0
#define GL_SAMPLE_BUFFERS_ARB             0x80A8
#define GL_SAMPLES_ARB                    0x80A9
#define GL_SAMPLE_COVERAGE_VALUE_ARB      0x80AA
#define GL_SAMPLE_COVERAGE_INVERT_ARB     0x80AB
#define GL_MULTISAMPLE_BIT_ARB            0x20000000
#endif
#ifndef GL_NV_multisample_filter_hint
#define GL_MULTISAMPLE_FILTER_HINT_NV     0x8534
#endif


namespace osg {

/** Multisample - encapsulates the OpenGL Multisample state.*/
class OSG_EXPORT Multisample : public StateAttribute
{
    public :

        enum Mode
        {
            FASTEST = GL_FASTEST, 
            NICEST = GL_NICEST,
            DONT_CARE = GL_DONT_CARE 
        };

        Multisample();
        
        /** Copy constructor using CopyOp to manage deep vs shallow copy.*/
        Multisample(const Multisample& trans,const CopyOp& copyop=CopyOp::SHALLOW_COPY):
            StateAttribute(trans,copyop),
            _coverage(trans._coverage),
            _invert(trans._invert),
            _mode(trans._mode) {}

        META_StateAttribute(osg, Multisample,MULTISAMPLE);
        
        /** return -1 if *this < *rhs, 0 if *this==*rhs, 1 if *this>*rhs.*/
        virtual int compare(const StateAttribute& sa) const
        {
            // check the types are equal and then create the rhs variable
            // used by the COMPARE_StateAttribute_Parameter macros below.
            COMPARE_StateAttribute_Types(Multisample,sa)

            // compare each parameter in turn against the rhs.
            COMPARE_StateAttribute_Parameter(_coverage)
            COMPARE_StateAttribute_Parameter(_invert)
            COMPARE_StateAttribute_Parameter(_mode)

            return 0; // passed all the above comparison macros, must be equal.
        }

        void setSampleCoverage(float coverage, bool invert) 
        {
            _coverage = coverage; 
            _invert = invert;
        }
        inline void setCoverage(float coverage) { _coverage=coverage; }
        inline float getCoverage() const { return _coverage; }
    
        inline void setInvert(bool invert) { _invert=invert; }
        inline bool getInvert() const { return _invert; }

        inline void setHint(Mode mode) { _mode = mode; }
        inline Mode getHint() const { return _mode; }

        virtual void apply(State& state) 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 OSG_EXPORT Extensions : public osg::Referenced
        {
            public:
                Extensions(unsigned int contextID);

                Extensions(const Extensions& rhs);
                
                void lowestCommonDenominator(const Extensions& rhs);
                
                void setupGLExtensions(unsigned int contextID);

                void setMultisampleSupported(bool flag) { _isMultisampleSupported=flag; }
                void setMultisampleFilterHintSupported(bool flag) { _isMultisampleFilterHintSupported=flag; }
                bool isMultisampleSupported() const { return _isMultisampleSupported; }
                bool isMultisampleFilterHintSupported() const { return _isMultisampleFilterHintSupported; }
                
                void glSampleCoverage(GLclampf value, GLboolean invert) const;

            protected:

                ~Extensions() {}
                
                bool    _isMultisampleSupported;
                bool    _isMultisampleFilterHintSupported;
                
                typedef void (GL_APIENTRY * GLSampleCoverageProc) (GLclampf value, GLboolean invert);
                GLSampleCoverageProc _glSampleCoverage;

        };
        
        /** Function to call to get the extension of a specified context.
          * If the Extension 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 will
          * 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 :

        virtual ~Multisample();

        float _coverage;
        bool _invert;
        Mode _mode;
};

}

#endif