--------------------------------------------------------------------------------
-- |
-- Module      :  Graphics.Rendering.OpenGL.GL.BeginEnd
-- Copyright   :  (c) Sven Panne 2002-2019
-- License     :  BSD3
--
-- Maintainer  :  Sven Panne <svenpanne@gmail.com>
-- Stability   :  stable
-- Portability :  portable
--
-- This module corresponds to section 10.8 (Drawing Commands Using Begin and
-- End) of the OpenGL 4.4 specs.
--
--------------------------------------------------------------------------------

module Graphics.Rendering.OpenGL.GL.BeginEnd (
   -- * Begin and End Objects
   renderPrimitive, unsafeRenderPrimitive, primitiveRestart,

   -- * Polygon Edges
   EdgeFlag(..),
   edgeFlag
) where

import Data.StateVar
import Graphics.Rendering.OpenGL.GL.EdgeFlag
import Graphics.Rendering.OpenGL.GL.Exception
import Graphics.Rendering.OpenGL.GL.PrimitiveMode
import Graphics.Rendering.OpenGL.GL.PrimitiveModeInternal
import Graphics.Rendering.OpenGL.GL.QueryUtils
import Graphics.GL

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

-- | Delimit the vertices that define a primitive or a group of like primitives.
--
-- Only a subset of GL commands can be used in the delimited action:
-- Those for specifying vertex coordinates
-- ('Graphics.Rendering.OpenGL.GL.VertexSpec.vertex',
--  'Graphics.Rendering.OpenGL.GL.VertexSpec.vertexv'),
-- vertex colors
-- ('Graphics.Rendering.OpenGL.GL.VertexSpec.color',
--  'Graphics.Rendering.OpenGL.GL.VertexSpec.colorv',
--  'Graphics.Rendering.OpenGL.GL.VertexSpec.secondaryColor',
--  'Graphics.Rendering.OpenGL.GL.VertexSpec.secondaryColorv',
--  'Graphics.Rendering.OpenGL.GL.VertexSpec.index',
--  'Graphics.Rendering.OpenGL.GL.VertexSpec.indexv'),
-- normal
-- ('Graphics.Rendering.OpenGL.GL.VertexSpec.normal',
--  'Graphics.Rendering.OpenGL.GL.VertexSpec.normalv'),
-- texture coordinates
-- ('Graphics.Rendering.OpenGL.GL.VertexSpec.texCoord',
--  'Graphics.Rendering.OpenGL.GL.VertexSpec.texCoordv',
--  'Graphics.Rendering.OpenGL.GL.VertexSpec.multiTexCoord',
--  'Graphics.Rendering.OpenGL.GL.VertexSpec.multiTexCoordv'),
-- and fog coordinates
-- ('Graphics.Rendering.OpenGL.GL.VertexSpec.fogCoord',
--  'Graphics.Rendering.OpenGL.GL.VertexSpec.fogCoordv').
-- Additionally,
-- 'Graphics.Rendering.OpenGL.GL.Evaluators.evalPoint1',
-- 'Graphics.Rendering.OpenGL.GL.Evaluators.evalPoint2',
-- 'Graphics.Rendering.OpenGL.GL.Evaluators.evalCoord1',
-- 'Graphics.Rendering.OpenGL.GL.Evaluators.evalCoord1v',
-- 'Graphics.Rendering.OpenGL.GL.Evaluators.evalCoord2',
-- 'Graphics.Rendering.OpenGL.GL.Evaluators.evalCoord2v',
-- 'Graphics.Rendering.OpenGL.GL.Colors.materialAmbient',
-- 'Graphics.Rendering.OpenGL.GL.Colors.materialDiffuse',
-- 'Graphics.Rendering.OpenGL.GL.Colors.materialAmbientAndDiffuse',
-- 'Graphics.Rendering.OpenGL.GL.Colors.materialSpecular',
-- 'Graphics.Rendering.OpenGL.GL.Colors.materialEmission',
-- 'Graphics.Rendering.OpenGL.GL.Colors.materialShininess',
-- 'Graphics.Rendering.OpenGL.GL.DisplayLists.callList',
-- 'Graphics.Rendering.OpenGL.GL.DisplayLists.callLists',
-- and setting 'edgeFlag' are allowed. Writing the respective state variables
-- is allowed in the delimited action, too.
--
-- Regardless of the chosen 'PrimitiveMode', there is no limit to the number of
-- vertices that can be defined during a single 'renderPrimitive'. Lines,
-- triangles, quadrilaterals, and polygons that are incompletely specified are
-- not drawn. Incomplete specification results when either too few vertices are
-- provided to specify even a single primitive or when an incorrect multiple of
-- vertices is specified. The incomplete primitive is ignored; the rest are
-- drawn.
--
-- The minimum specification of vertices for each primitive is as follows: 1
-- for a point, 2 for a line, 3 for a triangle, 4 for a quadrilateral, and 3 for
-- a polygon. Modes that require a certain multiple of vertices are 'Lines' (2),
-- 'Triangles' (3), 'Quads' (4), and 'QuadStrip' (2).

renderPrimitive :: PrimitiveMode -> IO a -> IO a
renderPrimitive = renderPrim bracket_

-- | A more efficient, but potentially dangerous version of 'renderPrimitive':
-- The given action is not allowed to throw an exception.

unsafeRenderPrimitive :: PrimitiveMode -> IO a -> IO a
unsafeRenderPrimitive = renderPrim unsafeBracket_

{-# INLINE renderPrim #-}
renderPrim :: (IO () -> IO () -> IO a -> IO a) -> PrimitiveMode -> IO a -> IO a
renderPrim brack_ beginMode =
   brack_ (glBegin (marshalPrimitiveMode beginMode)) glEnd

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

primitiveRestart :: IO ()
primitiveRestart = glPrimitiveRestartNV

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

-- | Each vertex of a polygon, separate triangle, or separate quadrilateral
-- specified during 'renderPrimitive' is marked as the start of either a boundary
-- or nonboundary (interior) edge.
--
-- The vertices of connected triangles and connected quadrilaterals are always
-- marked as boundary, regardless of the value of the edge flag.
--
-- Boundary and nonboundary edge flags on vertices are significant only if
-- 'Graphics.Rendering.OpenGL.GL.Polygons.polygonMode' is set to
-- 'Graphics.Rendering.OpenGL.GL.Polygons.Point' or
-- 'Graphics.Rendering.OpenGL.GL.Polygons.Line'.
--
-- Note that the current edge flag can be updated at any time, in particular
-- during 'renderPrimitive'.

edgeFlag :: StateVar EdgeFlag
edgeFlag =
   makeStateVar (getBoolean1 unmarshalEdgeFlag GetEdgeFlag)
                (glEdgeFlag . marshalEdgeFlag)
