SFML/include/SFML/Graphics/BlendMode.hpp

////////////////////////////////////////////////////////////
//
// SFML - Simple and Fast Multimedia Library
// Copyright (C) 2007-2014 Laurent Gomila (laurent.gom@gmail.com)
//
// 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.
//
////////////////////////////////////////////////////////////

#ifndef SFML_BLENDMODE_HPP
#define SFML_BLENDMODE_HPP

////////////////////////////////////////////////////////////
// Headers
////////////////////////////////////////////////////////////
#include <SFML/Graphics/Export.hpp>


namespace sf
{

////////////////////////////////////////////////////////////
/// \ingroup graphics
/// \brief Blending modes for drawing
///
////////////////////////////////////////////////////////////
struct SFML_GRAPHICS_API BlendMode
{
    ////////////////////////////////////////////////////////
    /// \ingroup graphics
    /// \brief Enumeration of the blending factors
    ///
    ////////////////////////////////////////////////////////
    enum Factor
    {
        Zero,             ///< (0, 0, 0, 0)
        One,              ///< (1, 1, 1, 1)
        SrcColor,         ///< (src.r, src.g, src.b, src.a)
        OneMinusSrcColor, ///< (1, 1, 1, 1) - (src.r, src.g, src.b, src.a)
        DstColor,         ///< (dst.r, dst.g, dst.b, dst.a)
        OneMinusDstColor, ///< (1, 1, 1, 1) - (dst.r, dst.g, dst.b, dst.a)
        SrcAlpha,         ///< (src.a, src.a, src.a, src.a)
        OneMinusSrcAlpha, ///< (1, 1, 1, 1) - (src.a, src.a, src.a, src.a)
        DstAlpha,         ///< (dst.a, dst.a, dst.a, dst.a)
        OneMinusDstAlpha  ///< (1, 1, 1, 1) - (dst.a, dst.a, dst.a, dst.a)
    };

    ////////////////////////////////////////////////////////
    /// \ingroup graphics
    /// \brief Enumeration of the blending equations
    ///
    ////////////////////////////////////////////////////////
    enum Equation
    {
        Add,     ///< Pixel = Src * SrcFactor + Dst * DstFactor
        Subtract ///< Pixel = Src * SrcFactor - Dst * DstFactor
    };

    ////////////////////////////////////////////////////////////
    /// \brief Default constructor
    ///
    /// Constructs a blending mode that does alpha blending.
    ///
    ////////////////////////////////////////////////////////////
    BlendMode();

    ////////////////////////////////////////////////////////////
    /// \brief Construct the blend mode given the factors and equation.
    ///
    /// \param colorSourceFactor      Specifies how to compute the source factor for the color channels.
    /// \param colorDestinationFactor Specifies how to compute the destination factor for the color channels.
    /// \param colorBlendEquation     Specifies how to combine the source and destination colors.
    /// \param alphaSourceFactor      Specifies how to compute the source factor.
    /// \param alphaDestinationFactor Specifies how to compute the destination factor.
    /// \param alphaBlendEquation     Specifies how to combine the source and destination alphas.
    ///
    ////////////////////////////////////////////////////////////
    BlendMode(Factor colorSourceFactor, Factor colorDestinationFactor,
              Equation colorBlendEquation, Factor alphaSourceFactor,
              Factor alphaDestinationFactor, Equation alphaBlendEquation);

    ////////////////////////////////////////////////////////////
    // Member Data
    ////////////////////////////////////////////////////////////
    Factor   colorSrcFactor; ///< Source blending factor for the color channels
    Factor   colorDstFactor; ///< Destination blending factor for the color channels
    Equation colorEquation;  ///< Blending equation for the color channels
    Factor   alphaSrcFactor; ///< Source blending factor for the alpha channel
    Factor   alphaDstFactor; ///< Destination blending factor for the alpha channel
    Equation alphaEquation;  ///< Blending equation for the alpha channel
};

////////////////////////////////////////////////////////////
/// \relates BlendMode
/// \brief Overload of the == operator
///
/// \param left  Left operand
/// \param right Right operand
///
/// \return True if blending modes are equal, false if they are different
///
////////////////////////////////////////////////////////////
SFML_GRAPHICS_API bool operator ==(const BlendMode& left, const BlendMode& right);

////////////////////////////////////////////////////////////
/// \relates BlendMode
/// \brief Overload of the != operator
///
/// \param left  Left operand
/// \param right Right operand
///
/// \return True if blending modes are different, false if they are equal
///
////////////////////////////////////////////////////////////
SFML_GRAPHICS_API bool operator !=(const BlendMode& left, const BlendMode& right);


////////////////////////////////////////////////////////////
// Commonly used blending modes
////////////////////////////////////////////////////////////
SFML_GRAPHICS_API extern const BlendMode BlendAlpha;
SFML_GRAPHICS_API extern const BlendMode BlendAdd;
SFML_GRAPHICS_API extern const BlendMode BlendMultiply;
SFML_GRAPHICS_API extern const BlendMode BlendNone;

} // namespace sf


#endif // SFML_BLENDMODE_HPP


////////////////////////////////////////////////////////////
/// \class sf::BlendMode
/// \ingroup graphics
///
/// sf::BlendMode is a class that represents a blend mode. A
/// blend mode is composed of 6 components:
/// \li %Color Source Factor (colorSrcFactor)
/// \li %Color Destination Factor (colorDstFactor)
/// \li %Color Blend Equation (colorEquation)
/// \li Alpha Source Factor (alphaSrcFactor)
/// \li Alpha Destination Factor (alphaDstFactor)
/// \li Alpha Blend Equation (alphaEquation)
///
/// Each component has its own public member variable. These make
/// modifying a blending mode rather easy:
///
/// \code
/// sf::BlendMode blendMode;                           // Standard alpha blending
/// blendMode.colorSrcFactor = sf::BlendMode::One;     // Pre-multiplied alpha blending
/// blendMode.colorEquation = sf::BlendMode::Subtract; // An exotic subtraction blending mode
/// \endcode
///
/// The most common blending modes are defined as constants
/// in the sf namespace, for convenience and compatibility with
/// older code:
///
/// \code
/// sf::BlendMode alphaBlending          = sf::BlendAlpha;
/// sf::BlendMode additiveBlending       = sf::BlendAdd;
/// sf::BlendMode multiplicativeBlending = sf::BlendMultipy;
/// sf::BlendMode noBlending             = sf::BlendNone;
/// \endcode
///
////////////////////////////////////////////////////////////