The intelligent diagram is a recent metaphor for diagramming in which the underlying graphic editor parses the diagram as it is being constructed, performing error correction and collecting geometric constraints which capture the relationships between diagram components.During diagram manipulation a constraint solver uses these geometric constraints to maintain the diagram's semantics.We describe the Penguins system.This automates the development of graphical editors that support the intelligent diagram metaphor.It takes a grammatical specification of a particular diagram language and generates an editor that supports the creation, manipulation and parsing of diagrams in that visual language.Our empirical results show that the system can be used to generate specialized editors for a wide variety of diagram languages, ranging from state transition diagrams to mathematical equations, with real-time incremental parsing, error correction and direct manipulation.