Confusing type names: Graphic and Graphic2D

[apblack]

The type Graphic2D is a specialization of type Graphic that adds methods for interrogating the size of, and resizing, the object. This is not apparent from the names.

Worse, there is no type that represents a Graphic with a size. Class

drawable2DAt (location': Point)
      size (dimension': Point)
      on (canvas': DrawingCanvas)

claimed that it generated a Graphic2D, when it actually generates a

Graphic & interface {
    width -> Number
    height -> Number
    size -> Point
}

When the compiler started generating a check for the return types, it failed. Commit f0e8b71 corrects the code.

However, errors like this are easy to make with such non-mnemonic names. I suggest either that all Graphics have a size, or, if this is infeasible, that we use three types Graphic, SizableGraphic, and ResizableGraphic. Add the 2D suffix to all of them if you like.