text: ////////////////////////////////////////////////////////////
  //
  // SFML - Simple and Fast Multimedia Library
  // Copyright (C) 2007-2018 Laurent Gomila (laurent@sfml-dev.org)
  //
  // 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_RENDERTARGET_HPP
  #define SFML_RENDERTARGET_HPP
  
  ////////////////////////////////////////////////////////////
  // Headers
  ////////////////////////////////////////////////////////////
  #include <SFML/Graphics/BlendMode.hpp>
  #include <SFML/Graphics/Color.hpp>
  #include <SFML/Graphics/Export.hpp>
  #include <SFML/Graphics/PrimitiveType.hpp>
  #include <SFML/Graphics/Rect.hpp>
  #include <SFML/Graphics/RenderStates.hpp>
  #include <SFML/Graphics/Transform.hpp>
  #include <SFML/Graphics/Vertex.hpp>
  #include <SFML/Graphics/View.hpp>
  #include <SFML/System/NonCopyable.hpp>
  
  namespace sf {
  class Drawable;
  class VertexBuffer;
  
  ////////////////////////////////////////////////////////////
  /// \brief Base class for all render targets (window, texture, ...)
  ///
  ////////////////////////////////////////////////////////////
  class SFML_GRAPHICS_API RenderTarget : NonCopyable {
  public:
    ////////////////////////////////////////////////////////////
    /// \brief Destructor
    ///
    ////////////////////////////////////////////////////////////
    virtual ~RenderTarget();
  
    ////////////////////////////////////////////////////////////
    /// \brief Clear the entire target with a single color
    ///
    /// This function is usually called once every frame,
    /// to clear the previous contents of the target.
    ///
    /// \param color Fill color to use to clear the render target
    ///
    ////////////////////////////////////////////////////////////
    void clear(const Color &color = Color(0, 0, 0, 255));
  
    ////////////////////////////////////////////////////////////
    /// \brief Change the current active view
    ///
    /// The view is like a 2D camera, it controls which part of
    /// the 2D scene is visible, and how it is viewed in the
    /// render target.
    /// The new view will affect everything that is drawn, until
    /// another view is set.
    /// The render target keeps its own copy of the view object,
    /// so it is not necessary to keep the original one alive
    /// after calling this function.
    /// To restore the original view of the target, you can pass
    /// the result of getDefaultView() to this function.
    ///
    /// \param view New view to use
    ///
    /// \see getView, getDefaultView
    ///
    ////////////////////////////////////////////////////////////
    void setView(const View &view);
  
    ////////////////////////////////////////////////////////////
    /// \brief Get the view currently in use in the render target
    ///
    /// \return The view object that is currently used
    ///
    /// \see setView, getDefaultView
    ///
    ////////////////////////////////////////////////////////////
    const View &getView() const;
  
    ////////////////////////////////////////////////////////////
    /// \brief Get the default view of the render target
    ///
    /// The default view has the initial size of the render target,
    /// and never changes after the target has been created.
    ///
    /// \return The default view of the render target
    ///
    /// \see setView, getView
    ///
    ////////////////////////////////////////////////////////////
    const View &getDefaultView() const;
  
    ////////////////////////////////////////////////////////////
    /// \brief Get the viewport of a view, applied to this render target
    ///
    /// The viewport is defined in the view as a ratio, this function
    /// simply applies this ratio to the current dimensions of the
    /// render target to calculate the pixels rectangle that the viewport
    /// actually covers in the target.
    ///
    /// \param view The view for which we want to compute the viewport
    ///
    /// \return Viewport rectangle, expressed in pixels
    ///
    ////////////////////////////////////////////////////////////
    IntRect getViewport(const View &view) const;
  
    ////////////////////////////////////////////////////////////
    /// \brief Convert a point from target coordinates to world
    ///        coordinates, using the current view
    ///
    /// This function is an overload of the mapPixelToCoords
    /// function that implicitly uses the current view.
    /// It is equivalent to:
    /// \code
    /// target.mapPixelToCoords(point, target.getView());
    /// \endcode
    ///
    /// \param point Pixel to convert
    ///
    /// \return The converted point, in "world" coordinates
    ///
    /// \see mapCoordsToPixel
    ///
    ////////////////////////////////////////////////////////////
    Vector2f mapPixelToCoords(const Vector2i &point) const;
  
    ////////////////////////////////////////////////////////////
    /// \brief Convert a point from target coordinates to world coordinates
    ///
    /// This function finds the 2D position that matches the
    /// given pixel of the render target. In other words, it does
    /// the inverse of what the graphics card does, to find the
    /// initial position of a rendered pixel.
    ///
    /// Initially, both coordinate systems (world units and target pixels)
    /// match perfectly. But if you define a custom view or resize your
    /// render target, this assertion is not true anymore, i.e. a point
    /// located at (10, 50) in your render target may map to the point
    /// (150, 75) in your 2D world -- if the view is translated by (140, 25).
    ///
    /// For render-windows, this function is typically used to find
    /// which point (or object) is located below the mouse cursor.
    ///
    /// This version uses a custom view for calculations, see the other
    /// overload of the function if you want to use the current view of the
    /// render target.
    ///
    /// \param point Pixel to convert
    /// \param view The view to use for converting the point
    ///
    /// \return The converted point, in "world" units
    ///
    /// \see mapCoordsToPixel
    ///
    ////////////////////////////////////////////////////////////
    Vector2f mapPixelToCoords(const Vector2i &point, const View &view) const;
  
    ////////////////////////////////////////////////////////////
    /// \brief Convert a point from world coordinates to target
    ///        coordinates, using the current view
    ///
    /// This function is an overload of the mapCoordsToPixel
    /// function that implicitly uses the current view.
    /// It is equivalent to:
    /// \code
    /// target.mapCoordsToPixel(point, target.getView());
    /// \endcode
    ///
    /// \param point Point to convert
    ///
    /// \return The converted point, in target coordinates (pixels)
    ///
    /// \see mapPixelToCoords
    ///
    ////////////////////////////////////////////////////////////
    Vector2i mapCoordsToPixel(const Vector2f &point) const;
  
    ////////////////////////////////////////////////////////////
    /// \brief Convert a point from world coordinates to target coordinates
    ///
    /// This function finds the pixel of the render target that matches
    /// the given 2D point. In other words, it goes through the same process
    /// as the graphics card, to compute the final position of a rendered point.
    ///
    /// Initially, both coordinate systems (world units and target pixels)
    /// match perfectly. But if you define a custom view or resize your
    /// render target, this assertion is not true anymore, i.e. a point
    /// located at (150, 75) in your 2D world may map to the pixel
    /// (10, 50) of your render target -- if the view is translated by (140, 25).
    ///
    /// This version uses a custom view for calculations, see the other
    /// overload of the function if you want to use the current view of the
    /// render target.
    ///
    /// \param point Point to convert
    /// \param view The view to use for converting the point
    ///
    /// \return The converted point, in target coordinates (pixels)
    ///
    /// \see mapPixelToCoords
    ///
    ////////////////////////////////////////////////////////////
    Vector2i mapCoordsToPixel(const Vector2f &point, const View &view) const;
  
    ////////////////////////////////////////////////////////////
    /// \brief Draw a drawable object to the render target
    ///
    /// \param drawable Object to draw
    /// \param states   Render states to use for drawing
    ///
    ////////////////////////////////////////////////////////////
    void draw(const Drawable &drawable,
              const RenderStates &states = RenderStates::Default);
  
    ////////////////////////////////////////////////////////////
    /// \brief Draw primitives defined by an array of vertices
    ///
    /// \param vertices    Pointer to the vertices
    /// \param vertexCount Number of vertices in the array
    /// \param type        Type of primitives to draw
    /// \param states      Render states to use for drawing
    ///
    ////////////////////////////////////////////////////////////
    void draw(const Vertex *vertices, std::size_t vertexCount, PrimitiveType type,
              const RenderStates &states = RenderStates::Default);
  
    ////////////////////////////////////////////////////////////
    /// \brief Draw primitives defined by a vertex buffer
    ///
    /// \param vertexBuffer Vertex buffer
    /// \param states       Render states to use for drawing
    ///
    ////////////////////////////////////////////////////////////
    void draw(const VertexBuffer &vertexBuffer,
              const RenderStates &states = RenderStates::Default);
  
    ////////////////////////////////////////////////////////////
    /// \brief Draw primitives defined by a vertex buffer
    ///
    /// \param vertexBuffer Vertex buffer
    /// \param firstVertex  Index of the first vertex to render
    /// \param vertexCount  Number of vertices to render
    /// \param states       Render states to use for drawing
    ///
    ////////////////////////////////////////////////////////////
    void draw(const VertexBuffer &vertexBuffer, std::size_t firstVertex,
              std::size_t vertexCount,
              const RenderStates &states = RenderStates::Default);
  
    ////////////////////////////////////////////////////////////
    /// \brief Return the size of the rendering region of the target
    ///
    /// \return Size in pixels
    ///
    ////////////////////////////////////////////////////////////
    virtual Vector2u getSize() const = 0;
  
    ////////////////////////////////////////////////////////////
    /// \brief Activate or deactivate the render target for rendering
    ///
    /// This function makes the render target's context current for
    /// future OpenGL rendering operations (so you shouldn't care
    /// about it if you're not doing direct OpenGL stuff).
    /// A render target's context is active only on the current thread,
    /// if you want to make it active on another thread you have
    /// to deactivate it on the previous thread first if it was active.
    /// Only one context can be current in a thread, so if you
    /// want to draw OpenGL geometry to another render target
    /// don't forget to activate it again. Activating a render
    /// target will automatically deactivate the previously active
    /// context (if any).
    ///
    /// \param active True to activate, false to deactivate
    ///
    /// \return True if operation was successful, false otherwise
    ///
    ////////////////////////////////////////////////////////////
    virtual bool setActive(bool active = true);
  
    ////////////////////////////////////////////////////////////
    /// \brief Save the current OpenGL render states and matrices
    ///
    /// This function can be used when you mix SFML drawing
    /// and direct OpenGL rendering. Combined with popGLStates,
    /// it ensures that:
    /// \li SFML's internal states are not messed up by your OpenGL code
    /// \li your OpenGL states are not modified by a call to a SFML function
    ///
    /// More specifically, it must be used around code that
    /// calls Draw functions. Example:
    /// \code
    /// // OpenGL code here...
    /// window.pushGLStates();
    /// window.draw(...);
    /// window.draw(...);
    /// window.popGLStates();
    /// // OpenGL code here...
    /// \endcode
    ///
    /// Note that this function is quite expensive: it saves all the
    /// possible OpenGL states and matrices, even the ones you
    /// don't care about. Therefore it should be used wisely.
    /// It is provided for convenience, but the best results will
    /// be achieved if you handle OpenGL states yourself (because
    /// you know which states have really changed, and need to be
    /// saved and restored). Take a look at the resetGLStates
    /// function if you do so.
    ///
    /// \see popGLStates
    ///
    ////////////////////////////////////////////////////////////
    void pushGLStates();
  
    ////////////////////////////////////////////////////////////
    /// \brief Restore the previously saved OpenGL render states and matrices
    ///
    /// See the description of pushGLStates to get a detailed
    /// description of these functions.
    ///
    /// \see pushGLStates
    ///
    ////////////////////////////////////////////////////////////
    void popGLStates();
  
    ////////////////////////////////////////////////////////////
    /// \brief Reset the internal OpenGL states so that the target is ready for
    /// drawing
    ///
    /// This function can be used when you mix SFML drawing
    /// and direct OpenGL rendering, if you choose not to use
    /// pushGLStates/popGLStates. It makes sure that all OpenGL
    /// states needed by SFML are set, so that subsequent draw()
    /// calls will work as expected.
    ///
    /// Example:
    /// \code
    /// // OpenGL code here...
    /// glPushAttrib(...);
    /// window.resetGLStates();
    /// window.draw(...);
    /// window.draw(...);
    /// glPopAttrib(...);
    /// // OpenGL code here...
    /// \endcode
    ///
    ////////////////////////////////////////////////////////////
    void resetGLStates();
  
  protected:
    ////////////////////////////////////////////////////////////
    /// \brief Default constructor
    ///
    ////////////////////////////////////////////////////////////
    RenderTarget();
  
    ////////////////////////////////////////////////////////////
    /// \brief Performs the common initialization step after creation
    ///
    /// The derived classes must call this function after the
    /// target is created and ready for drawing.
    ///
    ////////////////////////////////////////////////////////////
    void initialize();
  
  private:
    ////////////////////////////////////////////////////////////
    /// \brief Apply the current view
    ///
    ////////////////////////////////////////////////////////////
    void applyCurrentView();
  
    ////////////////////////////////////////////////////////////
    /// \brief Apply a new blending mode
    ///
    /// \param mode Blending mode to apply
    ///
    ////////////////////////////////////////////////////////////
    void applyBlendMode(const BlendMode &mode);
  
    ////////////////////////////////////////////////////////////
    /// \brief Apply a new transform
    ///
    /// \param transform Transform to apply
    ///
    ////////////////////////////////////////////////////////////
    void applyTransform(const Transform &transform);
  
    ////////////////////////////////////////////////////////////
    /// \brief Apply a new texture
    ///
    /// \param texture Texture to apply
    ///
    ////////////////////////////////////////////////////////////
    void applyTexture(const Texture *texture);
  
    ////////////////////////////////////////////////////////////
    /// \brief Apply a new shader
    ///
    /// \param shader Shader to apply
    ///
    ////////////////////////////////////////////////////////////
    void applyShader(const Shader *shader);
  
    ////////////////////////////////////////////////////////////
    /// \brief Setup environment for drawing
    ///
    /// \param useVertexCache Are we going to use the vertex cache?
    /// \param states         Render states to use for drawing
    ///
    ////////////////////////////////////////////////////////////
    void setupDraw(bool useVertexCache, const RenderStates &states);
  
    ////////////////////////////////////////////////////////////
    /// \brief Draw the primitives
    ///
    /// \param type        Type of primitives to draw
    /// \param firstVertex Index of the first vertex to use when drawing
    /// \param vertexCount Number of vertices to use when drawing
    ///
    ////////////////////////////////////////////////////////////
    void drawPrimitives(PrimitiveType type, std::size_t firstVertex,
                        std::size_t vertexCount);
  
    ////////////////////////////////////////////////////////////
    /// \brief Clean up environment after drawing
    ///
    /// \param states Render states used for drawing
    ///
    ////////////////////////////////////////////////////////////
    void cleanupDraw(const RenderStates &states);
  
    ////////////////////////////////////////////////////////////
    /// \brief Render states cache
    ///
    ////////////////////////////////////////////////////////////
    struct StatesCache {
      enum { VertexCacheSize = 4 };
  
      bool enable;             ///< Is the cache enabled?
      bool glStatesSet;        ///< Are our internal GL states set yet?
      bool viewChanged;        ///< Has the current view changed since last draw?
      BlendMode lastBlendMode; ///< Cached blending mode
      Uint64 lastTextureId;    ///< Cached texture
      bool texCoordsArrayEnabled; ///< Is GL_TEXTURE_COORD_ARRAY client state
                                  ///< enabled?
      bool useVertexCache;        ///< Did we previously use the vertex cache?
      Vertex vertexCache[VertexCacheSize]; ///< Pre-transformed vertices cache
    };
  
    ////////////////////////////////////////////////////////////
    // Member data
    ////////////////////////////////////////////////////////////
    View m_defaultView;  ///< Default view
    View m_view;         ///< Current view
    StatesCache m_cache; ///< Render states cache
    Uint64 m_id;         ///< Unique number that identifies the RenderTarget
  };
  
  } // namespace sf
  
  #endif // SFML_RENDERTARGET_HPP
  
  ////////////////////////////////////////////////////////////
  /// \class sf::RenderTarget
  /// \ingroup graphics
  ///
  /// sf::RenderTarget defines the common behavior of all the
  /// 2D render targets usable in the graphics module. It makes
  /// it possible to draw 2D entities like sprites, shapes, text
  /// without using any OpenGL command directly.
  ///
  /// A sf::RenderTarget is also able to use views (sf::View),
  /// which are a kind of 2D cameras. With views you can globally
  /// scroll, rotate or zoom everything that is drawn,
  /// without having to transform every single entity. See the
  /// documentation of sf::View for more details and sample pieces of
  /// code about this class.
  ///
  /// On top of that, render targets are still able to render direct
  /// OpenGL stuff. It is even possible to mix together OpenGL calls
  /// and regular SFML drawing commands. When doing so, make sure that
  /// OpenGL states are not messed up by calling the
  /// pushGLStates/popGLStates functions.
  ///
  /// \see sf::RenderWindow, sf::RenderTexture, sf::View
  ///
  ////////////////////////////////////////////////////////////
  