class AcGiDrawable : public AcRxObject;
All graphical objects, both transient and persistent, will implement a drawable interface. Objects exposing this interface are capable of drawing themselves through the Draw API.
All displayable objects are derived from AcGiDrawable (which is referred to throughout as a "drawable"). This class implements the protocol by which objects can be queried by the graphics system (GS) for their geometry, attributes, cache pointers, and database IDs.
A drawable need not have displayable output. Some drawables only affect attributes, transformations, or clipping regions; others contain other drawables and have no geometry or attributes of their own. AutoCAD's AcDbLayerTableRecord and AcDbBlockTableRecord classes are examples of such drawables.
A drawable need not be an AcDb database object. Two examples of non-persistent drawables are the UCS Icon and the Grid. These are visual elements of the AutoCAD editor that do not belong to an AcDb database.