NonPortable

A common, abstract base class for things that cannot be moved. You shouldn't use this class to create game objects directly; you should always use one of the concrete subclasses, such as Fixture or Immovable. This base class doesn't provide the full behavior necessary to make an object immovable; it's just here as a programming abstraction for the common elements of all immovable objects.

This class has two purposes. First, it defines some behavior common to all non-portable objects. Second, you can test an object to see if it's based on this class to determine whether it's a portable or unportable type of Thing.

class NonPortable : Thing

By default, if the object's contents would be listed in a direct examination, then also list them when showing an inventory list, or describing the enclosing room or an enclosing object.

An immovable objects is not listed in room or container contents listings. Since the object is immovable, it's in effect a permanent feature of its location, so it should be described as such: either directly as part of its location's description text, or via its own specialDesc.

Since non-portables aren't carried, their weight and bulk are largely irrelevant. Even so, when a non-portable is a component of another object, or otherwise contained in another object, its weight and/or bulk can affect the behavior of the parent object. So, it's simplest to use a default of zero for these so that there are no surprises about the parent's behavior.

Are my contents within a fixed item that is within the given location? Since we're fixed in place, our contents are certainly within a fixed item, so we merely need to check if we're fixed in place within the given location. We are if we're in the given location or we ourselves are fixed in place in the given location.

Thing decreases the likelihood that we want to examine an object when the object isn't being held. That's fine for portable objects, but nonportables can never be held, so we don't want that decrease in logicalness.

showing an immovable to someone simply requires that it be in sight: we're not holding it up to show it, we're simply pointing it out

Non-portable objects can't be held, since they can't be carried. However, in some cases, it's useful to include non-portable objects within an actor, such as when creating component parts of an actor (hands, say). In these cases, the non-portables aren't held, but rather are components or similar.

We're not being held, but if our location is an actor, then we're as good as held because we're effectively part of the actor.