Description:

lefty is a two-view graphics editor for technical pictures. This editor
has no hardwired knowledge about specific picture layouts or editing
operations. Each picture is described by a program that contains functions to
draw the picture and functions to perform editing operations that are
appropriate for the specific picture. Primitive user actions, like mouse and
keyboard events, are also bound to functions in this program.

Besides the graphical view of the picture itself, the editor presents a
textual view of the program that describes the picture. Programmability
and the two-view interface allow the editor to handle a variety of pictures,
but are particularly useful for pictures used in technical contexts, e.g.,
graphs and trees. Also, lefty can communicate with other processes.

This feature allows it to use existing tools to compute specific picture
layouts and allows external processes to use the editor as a front end to
display their data structures graphically.