Porting C# code. Is this a reference to a global object?

Question

I'm trying to port the Aether.Physics2D library from C# to Xojo. This is essentially a tweaked version of the Farseer physics engine. It's mostly done but there's one part of the source code that I can't work out (it may be because C# is not my main language).

In Dynamics/Contacts/Contact.cs there are multiple references to what looks like a global Collision object but I can't find it's definition. For instance, on line 405, in the switch:

case ContactType.Polygon:
  Collision.Collision.CollidePolygons(ref manifold, (PolygonShape)FixtureA.Shape, ref transformA, (PolygonShape)FixtureB.Shape, ref transformB);
  break;

I have already ported the Collision class and its CollidePolygons static method (defined here) but why is this code not just:

Collision.CollidePolygons(ref manifold, (PolygonShape)FixtureA.Shape, ref transformA, (PolygonShape)FixtureB.Shape, ref transformB);

Instead of:

Collision.Collision.CollidePolygons(ref manifold, (PolygonShape)FixtureA.Shape, ref transformA, (PolygonShape)FixtureB.Shape, ref transformB);

Essentially, why are there two Collision calls?

Any help is greatly appreciated.

Answer 1

No, that's just because it's a class called Collision within a namespace called Collision:

namespace tainicom.Aether.Physics2D.Collision
{
    public static class Collision
    {
    }
}

If you're porting the code anyway, I'd strongly recommend that you fix this mistake.

You could also change the calling code with a using directive:

using Collision = tainicom.Aether.Physics2D.Collision.Collision;
...
// Calling the method is simpler now
Collision.CollidePolygons(...);

You might want to provide your alias with a different name, actually:

// TODO: Think of a better name to use :)
using CollisionClass = tainicom.Aether.Physics2D.Collision.Collision;
...
CollisionClass.CollidePolygons(...);

That way the name Collision doesn't change its meaning at all, but you don't need to use Collision.Collision anywhere.