Blend.h

/*
 * Gamedev Framework (gf)
 * Copyright (C) 2016-2021 Julien Bernard
 *
 * This software is provided 'as-is', without any express or implied
 * warranty.  In no event will the authors be held liable for any damages
 * arising from the use of this software.
 *
 * Permission is granted to anyone to use this software for any purpose,
 * including commercial applications, and to alter it and redistribute it
 * freely, subject to the following restrictions:
 *
 * 1. The origin of this software must not be misrepresented; you must not
 *    claim that you wrote the original software. If you use this software
 *    in a product, an acknowledgment in the product documentation would be
 *    appreciated but is not required.
 * 2. Altered source versions must be plainly marked as such, and must not be
 *    misrepresented as being the original software.
 * 3. This notice may not be removed or altered from any source distribution.
 *
 * Part of this file comes from SFML, with the same license:
 * Copyright (C) 2007-2015 Laurent Gomila (laurent@sfml-dev.org)
 */
#ifndef GF_BLEND_H
#define GF_BLEND_H

#include "GraphicsApi.h"

namespace gf {
#ifndef DOXYGEN_SHOULD_SKIP_THIS
inline namespace v1 {
#endif

  enum class BlendEquation {
    Add,              
    Substract,        
    ReverseSubstract, 
  };

  enum class BlendFactor {
    Zero,             
    One,              
    SrcColor,         
    OneMinusSrcColor, 
    DstColor,         
    OneMinusDstColor, 
    SrcAlpha,         
    OneMinusSrcAlpha, 
    DstAlpha,         
    OneMinusDstAlpha  
  };

  struct GF_GRAPHICS_API BlendMode {

    constexpr BlendMode()
    : colorSrcFactor(BlendFactor::One)
    , colorDstFactor(BlendFactor::Zero)
    , colorEquation(BlendEquation::Add)
    , alphaSrcFactor(BlendFactor::One)
    , alphaDstFactor(BlendFactor::Zero)
    , alphaEquation(BlendEquation::Add)
    {

    }

    constexpr BlendMode(BlendFactor sourceFactor, BlendFactor destinationFactor, BlendEquation equation = BlendEquation::Add)
    : colorSrcFactor(sourceFactor)
    , colorDstFactor(destinationFactor)
    , colorEquation(equation)
    , alphaSrcFactor(sourceFactor)
    , alphaDstFactor(destinationFactor)
    , alphaEquation(equation)
    {

    }

    constexpr BlendMode(BlendFactor colorSourceFactor, BlendFactor colorDestinationFactor, BlendEquation colorBlendEquation,
                BlendFactor alphaSourceFactor, BlendFactor alphaDestinationFactor, BlendEquation alphaBlendEquation)
    : colorSrcFactor(colorSourceFactor)
    , colorDstFactor(colorDestinationFactor)
    , colorEquation(colorBlendEquation)
    , alphaSrcFactor(alphaSourceFactor)
    , alphaDstFactor(alphaDestinationFactor)
    , alphaEquation(alphaBlendEquation)
    {

    }

    BlendFactor colorSrcFactor;   
    BlendFactor colorDstFactor;   
    BlendEquation colorEquation;  
    BlendFactor alphaSrcFactor;   
    BlendFactor alphaDstFactor;   
    BlendEquation alphaEquation;  
  };

  constexpr BlendMode BlendAlpha
  #ifndef DOXYGEN_SHOULD_SKIP_THIS
  = BlendMode(
    BlendFactor::SrcAlpha, BlendFactor::OneMinusSrcAlpha, BlendEquation::Add,
    BlendFactor::One, BlendFactor::OneMinusSrcAlpha, BlendEquation::Add
  )
  #endif
  ;

  constexpr BlendMode BlendAdd
  #ifndef DOXYGEN_SHOULD_SKIP_THIS
  = BlendMode(
    BlendFactor::SrcAlpha, BlendFactor::One, BlendEquation::Add,
    BlendFactor::One, BlendFactor::One, BlendEquation::Add
  )
  #endif
  ;

  constexpr BlendMode BlendMultiply
  #ifndef DOXYGEN_SHOULD_SKIP_THIS
  = BlendMode (BlendFactor::DstColor, BlendFactor::Zero)
  #endif
  ;

  constexpr BlendMode BlendNone
  #ifndef DOXYGEN_SHOULD_SKIP_THIS
  = BlendMode(BlendFactor::One, BlendFactor::Zero)
  #endif
  ;


  constexpr bool operator==(const BlendMode& lhs, const BlendMode& rhs) {
    return lhs.colorSrcFactor == rhs.colorSrcFactor
        && lhs.colorDstFactor == rhs.colorDstFactor
        && lhs.colorEquation  == rhs.colorEquation
        && lhs.alphaSrcFactor == rhs.alphaSrcFactor
        && lhs.alphaDstFactor == rhs.alphaDstFactor
        && lhs.alphaEquation  == rhs.alphaEquation;
  }

#ifndef DOXYGEN_SHOULD_SKIP_THIS
}
#endif
}

#endif // GF_BLEND_H