/* -*-c++-*- OpenSceneGraph - Copyright (C) 1998-2005 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_VIEWPORT
#define OSG_VIEWPORT 1

#include <osg/StateAttribute>
#include <osg/Matrix>

namespace osg {

/** Encapsulate OpenGL glViewport. */     
class OSG_EXPORT Viewport : public StateAttribute
{
    public :
        Viewport();
        
        Viewport(int x,int y,int width,int height):
            _x(x),
            _y(y),
            _width(width),
            _height(height) {}
            

        /** Copy constructor using CopyOp to manage deep vs shallow copy. */
        Viewport(const Viewport& vp,const CopyOp& copyop=CopyOp::SHALLOW_COPY):
            StateAttribute(vp,copyop),
            _x(vp._x),
            _y(vp._y),
            _width(vp._width),
            _height(vp._height) {}

        META_StateAttribute(osg, Viewport,VIEWPORT);
        
        /** 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_Paramter macro's below.
            COMPARE_StateAttribute_Types(Viewport,sa)

            // compare each paramter in turn against the rhs.
            COMPARE_StateAttribute_Parameter(_x)
            COMPARE_StateAttribute_Parameter(_y)
            COMPARE_StateAttribute_Parameter(_width)
            COMPARE_StateAttribute_Parameter(_height)
            
            return 0; // passed all the above comparison macro's, must be equal.
        }

        inline void setViewport(int x,int y,int width,int height)
        {
            _x = x;
            _y = y;
            _width = width;
            _height = height;
        }
        
        void getViewport(int& x,int& y,int& width,int& height) const
        {
            x = _x;
            y = _y;
            width = _width;
            height = _height;
        }

        inline int x() const { return _x; }
        inline int y() const { return _y; }
        inline int width() const { return _width; }
        inline int height() const { return _height; }

        inline bool valid() const { return _width!=0 && _height!=0; }

        /** Return the aspectRatio of the viewport, which is equal to width/height.
          * If height is zero, the potental division by zero is avoided by simply returning 1.0f.
        */
        inline float aspectRatio() const { if (_height!=0) return (float)_width/(float)_height; else return 1.0f; }
        
        /** Compute the Window Matrix which takes projected coords into Window coordinates.
          * To convert local coordinates into window coordinates use v_window = v_local * MVPW matrix,
          * where the MVPW matrix is ModelViewMatrix * ProjectionMatrix * WindowMatrix, the latter supplied by
          * Viewport::computeWindowMatrix(), the ModelView and Projection Matrix can either be sourced from the
          * current osg::State object, via osgUtil::SceneView or CullVisitor.
        */
        inline const osg::Matrix computeWindowMatrix() const
        {
            return osg::Matrix::translate(1.0f,1.0f,1.0f)*osg::Matrix::scale(0.5f*width(),0.5f*height(),0.5f);
        }

        virtual void apply(State& state) const;

    protected:
    
        virtual ~Viewport();

        int _x;
        int _y;
        int _width;
        int _height;

};

}

#endif
