crash on collision

[hengchu]

I'm using Hipmunk together with the Arrow-based FRP GUI package UISF: https://github.com/dwincort/UISF

Basically UISF is used to draw stuff onto the screen while Hipmunk does the number crunching. However, whenever a collision happens in the sample code below, Hipmunk crashes because a pointer passed to cpCollideShapes is not valid.

I have verified that HipmunkPlayground works fine in my environment (OSX 10.10.3, GHC 7.8.4), so it shouldn't be a bad installation.

You should be able to compile and run the code below, and if you remove the line that adds the static line segment, the program will not crash:

{-# LANGUAGE Arrows #-}

import Data.StateVar
import qualified Physics.Hipmunk as H
import FRP.UISF.SOE
import FRP.UISF
import FRP.UISF.UISF
import FRP.UISF.UITypes
import FRP.UISF.Widget (mkWidget)

main :: IO ()
main = do sp <- H.newSpace 
          body <- H.newBody 1.0 5.0
          H.position body $= H.Vector 0 0
          H.velocity body $= H.Vector 0 (-25)
          shape <- H.newShape body (H.Circle 5) (H.Vector 0 0)
          H.spaceAdd sp shape
          H.spaceAdd sp body

          static <- H.newBody H.infinity H.infinity
          seg <- H.newShape static (H.LineSegment (H.Vector 0 $ -20) (H.Vector 100 $ -20) 1) 0 
          H.spaceAdd sp (H.Static seg)

          runUI' $ Main.loop sp body

loop :: H.Space -> H.Body -> UISF () ()
loop sp body = proc _ -> do
  rec (next, dt) <- animation <<< delay 0 -< next
  pos  <- (arrowSimulation sp body) <<< delay 0 -< dt
  mwidget (0, 0) -< convert pos


animation :: UISF Time (Time, Time)
animation = proc i -> do
  dt <- delta -< i
  returnA -< (i+dt, dt)

delta :: UISF Time Time
delta = proc lasttime -> do
  n <- getTime -< ()
  returnA -< n - lasttime

monadicSimulation :: H.Space -> H.Body -> H.Time -> IO (H.Position)
monadicSimulation space body dt = do H.step space dt
                                     get . H.position $ body

arrowSimulation :: H.Space -> H.Body -> UISF (H.Time) (H.Position)
arrowSimulation space body = uisfPipe (monadicSimulation space body)

mwLayout :: Layout
mwLayout = makeLayout (Stretchy 100) (Stretchy 100)

type MWState = (Int, Int) -- (x, y) of the circle

mwCompute :: MWState -> MWState -> Rect -> UIEvent -> ((), MWState, DirtyBit)
mwCompute s _ _ _ = ((), s, True)

mwDraw :: Rect -> Bool -> MWState -> Graphic
mwDraw _ _ (x, y) =
  withColor Blue $ ellipse (x, y) (x+30, y+30)

mwidget :: MWState -> UISF MWState ()
mwidget initials = mkWidget initials mwLayout mwCompute mwDraw

convert :: H.Vector -> MWState
convert (H.Vector x y) = (round x, -round y)

[hengchu]

I'm actually working on upgrading Hipmunk to Chipmunk 6.2.2. After some initial testing, the above code actually works with 6.2.2. Hopefully I'll be able to submit a pull request soon.

[suzumiyasmith]

Is this project still active? Chipmunk is already upgraded to 7.0 version.

[meteficha]

Not really, sorry. It's a lot of effort to maintain it and I don't have interest in spending the time anymore.

[suzumiyasmith]

Well. It still works well with lts-8.18.
For the newer version, chipmunk api has some break changes. (I'm not good at C)
All in all, thanks for your devotion to hipmunk.