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Haskell graphics program closes too soon

I am writing a program using OpenGl and Haskell that should draw a rectangle when and where the mouse was clicked. However, the program closes as soon as I click and before drawing a rectangle.

import Graphics.Rendering.OpenGL
import Graphics.UI.GLUT
import Graphics.UI.GLUT.Callbacks.Window

main = do
  (progname, _) <- getArgsAndInitialize
  createWindow progname
  keyboardMouseCallback $= Just myKeyboardMouseCallback
  displayCallback $= display
  mainLoop

myKeyboardMouseCallback key keyState modifiers (Position x y) =
  case (key, keyState) of
    (MouseButton LeftButton, Down) -> do
      clear[ColorBuffer]
      let x = x :: GLfloat
      let y = y :: GLfloat
      renderPrimitive Quads $ do
        color $ (Color3 (1.0::GLfloat) 0 0)
        vertex $ (Vertex3 (x::GLfloat) y 0)
        vertex $ (Vertex3 (x::GLfloat) (y+0.2) 0)
        vertex $ (Vertex3 ((x+0.2)::GLfloat) (y+0.2) 0)
        vertex $ (Vertex3 ((x+0.2)::GLfloat) y 0)
      flush
    _ -> return ()

display = do
  clear [ColorBuffer]
  renderPrimitive Lines $ do
  flush

Is there something that makes the program end before one of the methods, or is it just a way for the computer to tell me that I cannot do this?

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1 answer

, . OpenGL OpenGL. displayCallback GLUT, .

: / GLUT, , . , , ; , , , (, EGL GLX X11).

: displayCallback. , GLUT , , , , .

(, OpenGL; ), , . - ( Data.IORef):

main = do
  -- ...

  -- Create a mutable variable that stores a Bool and a pair of floats
  mouseStateRef <- newIORef (False, (0, 0))

  -- Pass a reference to the mutable variable to the callbacks
  keyboardMouseCallback $= Just (myKeyboardMouseCallback mouseStateRef)
  displayCallback $= (display mouseStateRef)

myKeyboardMouseCallback mouseStateRef key keyState modifiers (Position x y) =
  case key of
    MouseButton LeftButton -> do
      -- Store the current mouse pressed state and coords in the reference
      writeIORef mouseStateRef (keyState == Pressed, (x, y))
    _ -> return ()

display mouseStateRef = do
  clear [ColorBuffer]

  -- Read the state stored in the mutable reference
  (pressed, (x, y)) <- readIORef mouseStateRef

  -- Draw the quad if the mouse button is pressed
  when pressed . renderPrimitive Quads $ do
    color $ (Color3 (1.0::GLfloat) 0 0)
    vertex $ (Vertex3 (x::GLfloat) y 0)
    vertex $ (Vertex3 (x::GLfloat) (y+0.2) 0)
    vertex $ (Vertex3 ((x+0.2)::GLfloat) (y+0.2) 0)
    vertex $ (Vertex3 ((x+0.2)::GLfloat) y 0)
  flush
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