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|
{-# LANGUAGE QuasiQuotes #-}
module Triangle where
import Graphics.Rendering.OpenGL as GL
import GI.Gtk as Gtk
import GI.Gdk.Objects
import Control.Concurrent
import Control.Monad
import Data.ByteString (ByteString)
import Foreign.Marshal (newArray)
import Foreign.Ptr
import Foreign.Storable
import UtilGL
fragment_source :: ByteString
fragment_source = [glslFragment|
#version 330
in vec4 inputColor;
out vec4 outputColor;
void main() {
outputColor = vec4(1.0f, 0.0f, 0.0f, 0.0f); //constant red. I know it's a poor shader
}
|]
vertex_source :: ByteString
vertex_source = [glslVertex|
#version 330
in vec4 position;
void main() { gl_Position = position; }
|]
data State = State
{ stProgram :: Maybe Program
, stBuffer :: Maybe BufferObject
}
initState :: IO (MVar State)
initState = newMVar State
{ stProgram = Nothing
, stBuffer = Nothing
}
drawTriangle :: MVar State -> IO ()
drawTriangle svar = withMVar svar $ \st -> do
forM_ ((,) <$> stProgram st <*> stBuffer st) $ \(program,position_buffer) -> do
-- Use our shaders
GL.currentProgram $= Just program
-- Use the vertices in our buffer
GL.bindBuffer ArrayBuffer $= Just position_buffer
GL.vertexAttribArray (GL.AttribLocation 0) $= GL.Enabled
GL.vertexAttribPointer (GL.AttribLocation 0) $= (GL.ToFloat,VertexArrayDescriptor 4 GL.Float 0 nullPtr)
-- Draw the three vertices as a triangle
GL.drawArrays Triangles 0 3
-- We finished using the buffers and program
GL.vertexAttribArray (GL.AttribLocation 0) $= GL.Disabled
GL.bindBuffer ArrayBuffer $= Nothing
render :: MVar State -> GLArea -> GLContext -> IO Bool
render svar w gl = do
putStrLn "render!"
me <- gLAreaGetError w
maybe id (\e _ -> print e) me $ do
-- Clear the viewport
GL.clearColor $= GL.Color4 0 0 0 1
GL.clear [ColorBuffer]
-- draw our object
drawTriangle svar
GL.flush
return True
realize :: MVar State -> GLArea -> IO ()
realize svar w = do
putStrLn "realize!"
gLAreaMakeCurrent w
me <- gLAreaGetError w
maybe id (\e _ -> print e) me $ do
ctx <- gLAreaGetContext w
-- We only use one VAO, so we always keep it bound
vao <- GL.genObjectName
GL.bindVertexArrayObject $= Just vao
(vertex_data_sz,vertex_data) <- do
ptr <- newArray [ GL.Vertex4 0 0.5 0 1
, GL.Vertex4 0.5 (-0.366) 0 1
, GL.Vertex4 (-0.5) (-0.366) 0 1
]
return ( fromIntegral $ 3 * sizeOf (GL.Vertex4 0 0 0 (0 :: Float) )
, ptr :: Ptr (GL.Vertex4 Float) )
-- This is the buffer that holds the vertices
buffer <- GL.genObjectName
GL.bindBuffer ArrayBuffer $= Just buffer
GL.bufferData ArrayBuffer $= (vertex_data_sz, vertex_data, StaticDraw)
GL.bindBuffer ArrayBuffer $= Nothing
mfrag <- makeShader FragmentShader fragment_source
mvert <- makeShader VertexShader vertex_source
mprog <- makeProgram mfrag mvert
modifyMVar_ svar $ \_ -> return State
{ stProgram = mprog
, stBuffer = Just buffer
}
return ()
unrealize :: MVar State -> GLArea -> IO ()
unrealize _ _ = do
putStrLn "unrealize!"
|
