    --------------------------------------------------------------------------------
    -- |
    -- Module      :  Graphics.Rendering.OpenGL.GL.Rectangles
    -- Copyright   :  (c) Sven Panne 2002-2006
    -- License     :  BSD-style (see the file libraries/OpenGL/LICENSE)
    --
    -- Maintainer  :  sven.panne@aedion.de
    -- Stability   :  stable
    -- Portability :  portable
    --
    -- This module corresponds to section 2.10 (Rectangles) of the OpenGL 2.1 specs.
    --
    --------------------------------------------------------------------------------

    module Graphics.Rendering.OpenGL.GL.Rectangles (
       Rect(..)
    ) where

    import Data.Int
    import Foreign.Ptr ( Ptr )
    import Graphics.Rendering.OpenGL.GL.BasicTypes (
       GLshort, GLint, GLfloat, GLdouble )
    import Graphics.Rendering.OpenGL.GL.VertexSpec ( Vertex2(..) )
    #ifdef __HADDOCK__
    import Graphics.Rendering.OpenGL.GL.BeginEnd ( PrimitiveMode(Polygon) )
    #endif

    --------------------------------------------------------------------------------

    #include "HsOpenGLExt.h"
    #include "HsOpenGLTypes.h"

    --------------------------------------------------------------------------------

    -- | 'rect' and 'rectv' support efficient specification of rectangles as two
    -- corner points. Each rectangle command takes four arguments, organized either
    -- as two consecutive pairs of (/x/, /y/) coordinates, or as two pointers to
    -- arrays, each containing an (/x/, /y/) pair. The resulting rectangle is
    -- defined in the /z/ = 0 plane.
    --
    -- @'rect' ('Vertex2' x1 y1) ('Vertex2' x2, y2)@ is exactly equivalent to the
    -- following sequence:
    --
    -- @
    --    'Graphics.Rendering.OpenGL.GL.BeginEnd.renderPrimitive' 'Graphics.Rendering.OpenGL.GL.BeginEnd.Polygon' $ do
    --        'Graphics.Rendering.OpenGL.GL.VertexSpec.vertex' ('Vertex2' x1 y1)
    --        'Graphics.Rendering.OpenGL.GL.VertexSpec.vertex' ('Vertex2' x2 y1)
    --        'Graphics.Rendering.OpenGL.GL.VertexSpec.vertex' ('Vertex2' x2 y2)
    --        'Graphics.Rendering.OpenGL.GL.VertexSpec.vertex' ('Vertex2' x1 y2)
    -- @
    --
    -- Note that if the second vertex is above and to the right of the first vertex,
    -- the rectangle is constructed with a counterclockwise winding.

    class Rect a where
       rect  :: Vertex2 a -> Vertex2 a -> IO ()
       rectv :: Ptr     a -> Ptr     a -> IO ()

    --------------------------------------------------------------------------------

    foreign import CALLCONV unsafe "glRects" glRects ::
       GLshort -> GLshort -> GLshort -> GLshort -> IO ()

    foreign import CALLCONV unsafe "glRectsv" glRectsv ::
       Ptr GLshort -> Ptr GLshort -> IO ()

    instance Rect GLshort_ where
       rect (Vertex2 x1 y1) (Vertex2 x2 y2) = glRects x1 y1 x2 y2
       rectv ptr1 ptr2 = glRectsv ptr1 ptr2

    --------------------------------------------------------------------------------

    foreign import CALLCONV unsafe "glRecti" glRecti ::
       GLint -> GLint -> GLint -> GLint -> IO ()

    foreign import CALLCONV unsafe "glRectiv" glRectiv ::
       Ptr GLint -> Ptr GLint -> IO ()

    instance Rect GLint_ where
       rect (Vertex2 x1 y1) (Vertex2 x2 y2) = glRecti x1 y1 x2 y2
       rectv ptr1 ptr2 = glRectiv ptr1 ptr2

    --------------------------------------------------------------------------------

    foreign import CALLCONV unsafe "glRectf" glRectf ::
       GLfloat -> GLfloat -> GLfloat -> GLfloat -> IO ()

    foreign import CALLCONV unsafe "glRectfv" glRectfv ::
       Ptr GLfloat -> Ptr GLfloat -> IO ()

    instance Rect GLfloat_ where
       rect (Vertex2 x1 y1) (Vertex2 x2 y2) = glRectf x1 y1 x2 y2
       rectv ptr1 ptr2 = glRectfv ptr1 ptr2

    --------------------------------------------------------------------------------

    foreign import CALLCONV unsafe "glRectd" glRectd ::
       GLdouble -> GLdouble -> GLdouble -> GLdouble -> IO ()

    foreign import CALLCONV unsafe "glRectdv" glRectdv ::
       Ptr GLdouble -> Ptr GLdouble -> IO ()

    instance Rect GLdouble_ where
       rect (Vertex2 x1 y1) (Vertex2 x2 y2) = glRectd x1 y1 x2 y2
       rectv ptr1 ptr2 = glRectdv ptr1 ptr2