love.physics: clean up some internal collision processing code

src/modules/physics/box2d/World.cpp

@@ -114,22 +114,6 @@ World::ContactFilter::~ContactFilter()
 
 bool World::ContactFilter::process(Shape *a, Shape *b)
 {
- // Handle masks, reimplemented from the manual
- int filterA[3], filterB[3];
- // [0] categoryBits
- // [1] maskBits
- // [2] groupIndex
- a->getFilterData(filterA);
- b->getFilterData(filterB);
-
- if (filterA[2] != 0 && // 0 is the default group, so this does not count
- filterA[2] == filterB[2]) // if they are in the same group
- return filterA[2] > 0; // Negative indexes mean you don't collide
-
- if ((filterA[1] & filterB[0]) == 0 ||
- (filterB[1] & filterA[0]) == 0)
- return false; // A and B aren't set to collide
-
  if (ref != nullptr && L != nullptr)
  {
  ref->push(L);
@@ -138,6 +122,7 @@ bool World::ContactFilter::process(Shape *a, Shape *b)
  lua_call(L, 2, 1);
  return luax_toboolean(L, -1);
  }
+
  return true;
 }
 
@@ -384,11 +369,24 @@ void World::PostSolve(b2Contact *contact, const b2ContactImpulse *impulse)
 
 bool World::ShouldCollide(b2Fixture *fixtureA, b2Fixture *fixtureB)
 {
+ const b2Filter &filterA = fixtureA->GetFilterData();
+ const b2Filter &filterB = fixtureB->GetFilterData();
+
+ // From b2_world_callbacks.cpp
+ // 0 is the default group index. If they're customized to be the same group,
+ // allow collisions if it's positive and disallow if it's negative.
+ if (filterA.groupIndex != 0 && filterA.groupIndex == filterB.groupIndex)
+ return filterA.groupIndex > 0;
+
+ if ((filterA.maskBits & filterB.categoryBits) == 0 || (filterA.categoryBits & filterB.maskBits) == 0)
+ return false;
+
  // Shapes should be memoized, if we created them
  Shape *a = (Shape *)(fixtureA->GetUserData().pointer);
  Shape *b = (Shape *)(fixtureB->GetUserData().pointer);
  if (!a || !b)
  throw love::Exception("A Shape has escaped Memoizer!");
+
  return filter.process(a, b);
 }