canvas/app/Renderer.hs

module Renderer where

import SDL (($=))

import qualified Graphics.Rendering.OpenGL as GL
import qualified Graphics.GLUtil as GLU

import qualified Data.Map.Strict as M

import qualified Data.ByteString as BS

import Codec.Picture

import Linear

import Foreign

-- internal imports

import Types

initSpriteRenderObjects = do
  quadVAO <- GL.genObjectName
  quadVBO <- GL.genObjectName

  GL.bindBuffer GL.ArrayBuffer $= Just quadVBO
  withArray rawVertices $ \ptr ->
    GL.bufferData GL.ArrayBuffer $=
      ( fromIntegral $ length rawVertices * sizeOf (0 :: Float)
      , ptr
      , GL.StaticDraw
      )

  GL.bindVertexArrayObject $= Just quadVAO

  GL.vertexAttribArray (GL.AttribLocation 0) $= GL.Enabled

  GL.vertexAttribPointer (GL.AttribLocation 0) $=
    ( GL.ToFloat
    , GL.VertexArrayDescriptor 4 GL.Float 0 (plusPtr nullPtr 0)
    )

  GL.bindBuffer GL.ArrayBuffer $= Nothing
  GL.bindVertexArrayObject $= Nothing

  return (SpriteRenderObjects quadVAO quadVBO)
  where
    rawVertices :: [Float]
    rawVertices =
      [ 0, 1, 0, 0
      , 1, 0, 1, 0
      , 0, 0, 0, 0
    
      , 0, 1, 0, 1
      , 1, 1, 1, 1
      , 1, 0, 1, 0
      ]

initSpriteShaderObjects = do
  vertexShaderSrc <- BS.readFile "shader/vertex.sl"
  fragmentShaderSrc <- BS.readFile "shader/fragment.sl"

  shaderProgram <- GLU.simpleShaderProgramBS vertexShaderSrc fragmentShaderSrc

  return (SpriteShaderObjects shaderProgram)

loadSprites :: IO (AssetDetails SpriteRenderObjects SpriteShaderObjects Sprite)
loadSprites = do
  rawImg <- readImage "assets/img/lynx.jpg"
  let img = case rawImg of
        Left err -> error err
        Right dynImg -> convertRGBA8 dynImg

  vertObj <- initSpriteRenderObjects
  shadObj <- initSpriteShaderObjects

  return AssetDetails
    { adVertObj = vertObj
    , adShadObj = shadObj
    , adDataObj = M.singleton "lynx" (Sprite (V2 0 0) img)
    }