// Copyright (C) 2002-2007 Nikolaus Gebhardt
// This file is part of the "Irrlicht Engine".
// For conditions of distribution and use, see copyright notice in irrlicht.h

#ifndef __I_SHADER_CONSTANT_SET_CALLBACT_H_INCLUDED__
#define __I_SHADER_CONSTANT_SET_CALLBACT_H_INCLUDED__

#include "IReferenceCounted.h"

namespace irr
{
namespace video
{
	class IMaterialRendererServices;

//! Interface making it possible to set constants for gpu programs every frame.
/** Implement this interface in an own class and pass a pointer to it to one of the methods in
 IGPUProgrammingServices when creating a shader. The OnSetConstants method will be called
 every frame now. */
class IShaderConstantSetCallBack : public virtual IReferenceCounted
{
public:

	//! Destructor.
	virtual ~IShaderConstantSetCallBack() {}


	//! Called to let the callBack know the used material (optional method)
	/**
	 \code
	class MyCallBack : public IShaderConstantSetCallBack
	{
		const video::SMaterial *UsedMaterial;

		OnSetMaterial(const video::SMaterial& material)
		{
			UsedMaterial=&material;
		}

		OnSetConstants(IMaterialRendererServices* services, s32 userData)
		{
			services->setVertexShaderConstant("myColor", reinterpret_cast<f32*>(&UsedMaterial->color), 4);
		}
	}
	\endcode
	*/
	virtual void OnSetMaterial(const SMaterial& material) { }

	//! Called by the engine when the vertex and/or pixel shader constants for an material renderer should be set.
	/**
	 Implement the IShaderConstantSetCallBack in an own class and implement your own
	 OnSetConstants method using the given IMaterialRendererServices interface.
	 Pass a pointer to this class to one of the methods in IGPUProgrammingServices
	 when creating a shader. The OnSetConstants method will now be called every time
	 before geometry is being drawn using your shader material. A sample implementation
	 would look like this:
	 \code
	 virtual void OnSetConstants(video::IMaterialRendererServices* services, s32 userData)
	 {
	   video::IVideoDriver* driver = services->getVideoDriver();

	   // set clip matrix at register 4
	   core::matrix4 worldViewProj(driver->getTransform(video::ETS_PROJECTION));
	   worldViewProj *= driver->getTransform(video::ETS_VIEW);
	   worldViewProj *= driver->getTransform(video::ETS_WORLD);
	   services->setVertexShaderConstant(&worldViewProj.M[0], 4, 4);
	   // for high level shading languages, this would be another solution:
	   //services->setVertexShaderConstant("mWorldViewProj", worldViewProj.M, 16);

	   // set some light color at register 9
	   video::SColorf col(0.0f,1.0f,1.0f,0.0f);
	   services->setVertexShaderConstant(reinterpret_cast<const f32*>(&col), 9, 1);
	   // for high level shading languages, this would be another solution:
	   //services->setVertexShaderConstant("myColor", reinterpret_cast<f32*>(&col), 4);
	 }
	 \endcode
	 \param services: Pointer to an interface providing methods to set the constants for the shader.
	 \param userData: Userdata int which can be specified when creating the shader.
	*/
	virtual void OnSetConstants(IMaterialRendererServices* services, s32 userData) = 0;
};


} // end namespace video
} // end namespace irr

#endif

