Reproduction for box2d.js/emscripten bug.

gistfile1.txt

Box2D = require './box2d'

_createCollider = (body, id, radius) ->

  shape = new Box2D.b2CircleShape()
  shape.set_m_radius radius

  fixtureDef = new Box2D.b2FixtureDef()

  fixtureDef.set_density(1)
  fixtureDef.set_shape(shape)
  fixtureDef.set_userData(id)

  return body.CreateFixture fixtureDef

_createBody = (x, y) ->
  pos = new Box2D.b2Vec2(x, y)
  bodyDef = new Box2D.b2BodyDef()

  bodyDef.set_type Box2D.b2_dynamicBody

  bodyDef.set_position(pos)

  return world.CreateBody bodyDef

contactCount = 0
contactCb = new Box2D.b2ContactListener()
Box2D.customizeVTable(contactCb, [{
  original: Box2D.b2ContactListener.prototype.BeginContact,
  replacement:
    beginContact = (thsPtr, contactPtr) ->
      contact = Box2D.wrapPointer(contactPtr, Box2D.b2Contact)
      fixtureA = contact.GetFixtureA()
      fixtureB = contact.GetFixtureB()
      console.log 'BEGIN', fixtureA.GetUserData(), fixtureB.GetUserData()
      contactCount++
}])

Box2D.customizeVTable(contactCb, [{
  original: Box2D.b2ContactListener.prototype.EndContact
  replacement:
    endContact = (thsPtr, contactPtr) ->
      contact = Box2D.wrapPointer(contactPtr, Box2D.b2Contact)
      fixtureA = contact.GetFixtureA()
      fixtureB = contact.GetFixtureB()
      console.log 'END', fixtureA.GetUserData(), fixtureB.GetUserData()
}])

world = new Box2D.b2World(new Box2D.b2Vec2(0, 0))

world.SetContactListener(contactCb)


b1 = _createBody(1, 1)
f1 = _createCollider b1, 1, 1

b2 = _createBody(1, 5)
f2 = _createCollider b2, 2, 1

b2.SetLinearVelocity(new Box2D.b2Vec2(0, -0.5))

while contactCount == 0
  world.Step(0.1, 2, 2)

for i in [0...50]
  world.Step(0.1, 2, 2)

b2.SetLinearVelocity(new Box2D.b2Vec2(0, 0.5))

for i in [0...100]
  world.Step(0.1, 2, 2)

return