/*
-----------------------------------------------------------------------------
This source file is part of OGRE
    (Object-oriented Graphics Rendering Engine)
For the latest info, see http://ogre.sourceforge.net/

Copyright (c) 2000-2005 The OGRE Team
Also see acknowledgements in Readme.html

This program is free software; you can redistribute it and/or modify it under
the terms of the GNU Lesser General Public License as published by the Free Software
Foundation; either version 2 of the License, or (at your option) any later
version.

This program 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 GNU Lesser General Public License for more details.

You should have received a copy of the GNU Lesser General Public License along with
this program; if not, write to the Free Software Foundation, Inc., 59 Temple
Place - Suite 330, Boston, MA 02111-1307, USA, or go to
http://www.gnu.org/copyleft/lesser.txt.
-----------------------------------------------------------------------------
*/

#include "OgreGLHardwareOcclusionQuery.h"
#include "OgreException.h"

namespace Ogre {

bool GLHardwareOcclusionQuery::sUseArbQueries = false;
/**
  * This is a class that is the base class of the query class for 
  * hardware occlusion testing.
  *
  * @author Lee Sandberg email: lee@abcmedia.se
  *
  * Updated on 12/7/2004 by Chris McGuirk
  * - Implemented ARB_occlusion_query
  */

/**
  * Default object constructor
  * 
  */
GLHardwareOcclusionQuery::GLHardwareOcclusionQuery() 
{ 
	mPixelCount = 0; 
	mSkipCounter = 0;
	mSkipInterval = 0;

	// Check for hardware occlusion support
	// This is a hack to see if hw occlusion is supported. pointer is 0 if it's not supported.
	mHasOcclusionSupportARB = (glGenQueriesARB_ptr != 0);
	mHasOcclusionSupportNV = (glGenOcclusionQueriesNV_ptr != 0);

	if (sUseArbQueries && mHasOcclusionSupportARB)
		glGenQueriesARB_ptr(1, &mQueryID );	
	else if (!sUseArbQueries && mHasOcclusionSupportNV)
		glGenOcclusionQueriesNV_ptr(1, &mQueryID);
}

/**
  * Object destructor
  */
GLHardwareOcclusionQuery::~GLHardwareOcclusionQuery() 
{ 
	if (sUseArbQueries && mHasOcclusionSupportARB)
		glDeleteQueriesARB_ptr(1, &mQueryID);
	else if (!sUseArbQueries && mHasOcclusionSupportNV)
		glDeleteOcclusionQueriesNV_ptr(1, &mQueryID);  
}

//------------------------------------------------------------------
// Occlusion query functions (see base class documentation for this)
//--
void GLHardwareOcclusionQuery::beginOcclusionQuery() 
{ 
	//if (mSkipCounter >= mSkipInterval)  // otherwise no query ever issued if mSkipInterval = 0 !
	//	mSkipCounter = 0; if (mSkipCounter != 0) return;

	if (sUseArbQueries && mHasOcclusionSupportARB)
			glBeginQueryARB_ptr(GL_SAMPLES_PASSED_ARB, mQueryID);
	else if (!sUseArbQueries && mHasOcclusionSupportNV)
			glBeginOcclusionQueryNV_ptr(mQueryID);
}
	
void GLHardwareOcclusionQuery::endOcclusionQuery() 
{ 
	//if( mSkipCounter != 0) return;
	if (sUseArbQueries && mHasOcclusionSupportARB)
			glEndQueryARB_ptr(GL_SAMPLES_PASSED_ARB);
	else if (!sUseArbQueries && mHasOcclusionSupportNV)
			glEndOcclusionQueryNV_ptr();
//	mSkipCounter++;
		}

bool GLHardwareOcclusionQuery::pullOcclusionQuery( unsigned int* NumOfFragments, const HW_OCCLUSIONQUERY flag  ) 
{
	if (sUseArbQueries && mHasOcclusionSupportARB)
		glGetQueryObjectuivARB_ptr(mQueryID, GL_QUERY_RESULT_ARB, NumOfFragments);
	else if (!sUseArbQueries && mHasOcclusionSupportNV)
glGetOcclusionQueryuivNV_ptr(mQueryID, GL_PIXEL_COUNT_NV, NumOfFragments);
	else
		*NumOfFragments = 100000;		// Fails quietly

	mPixelCount = *NumOfFragments; 
	
	return true;
}

#ifdef GTP_VISIBILITY_MODIFIED_OGRE
	//------------------------------------------------------------------
bool GLHardwareOcclusionQuery::pullOcclusionQuery(unsigned int * NumOfFragments, 
												  const bool waitForResult, 
												  const HW_OCCLUSIONQUERY flag) 
{
	if (sUseArbQueries && mHasOcclusionSupportARB)	
	{
		int isAvailable = GL_TRUE;

		if (!waitForResult)
			glGetQueryivARB_ptr(mQueryID, GL_QUERY_RESULT_AVAILABLE_ARB, &isAvailable);
		
		if (isAvailable == GL_TRUE)
			glGetQueryObjectuivARB_ptr(mQueryID, GL_QUERY_RESULT_ARB, NumOfFragments);

		mPixelCount = *NumOfFragments;

		return isAvailable == GL_TRUE;
	} 
	else if (!sUseArbQueries && mHasOcclusionSupportNV)
		{
		unsigned int isAvailable = GL_TRUE;

		if (!waitForResult)
				glGetOcclusionQueryuivNV_ptr(mQueryID, GL_PIXEL_COUNT_AVAILABLE_NV, &isAvailable);

		if (isAvailable == GL_TRUE)
				glGetOcclusionQueryuivNV_ptr(mQueryID, GL_PIXEL_COUNT_NV, NumOfFragments);

		mPixelCount = *NumOfFragments; 

		return isAvailable == GL_TRUE;
		}
	
		// In case hardware occlusion isn't supported, every object is set visible.
		*NumOfFragments = 100000;		
		mPixelCount = *NumOfFragments; 

	return GL_TRUE;	
}

#endif // GTP_VIBILITY_MODIFIED_OGRE
}