Hi!
The class MOAbstractLayout is in the category Layout. However, I believe it belongs to the Core since the Core cannot work without this class. MOAbstractLayout defines applyOn:, which is invoked by MORoot>>applyLayout.
I will also rename MOAbstractLayout into MOLayout to keep the name short and consistent with MOShape (and not MOAbstractShape).
If someone is against this, let me know.
Cheers, Alexandre