Gypsy was the first document preparation system based on a mouse and graphical user interface to take advantage of those technologies to virtually eliminate modes.
It was the second WYSIWYG document preparation program, a successor to the Bravo on the Xerox Alto personal computer.
It was designed and implemented at Xerox PARC in 1975 by Larry Tesler and Timothy Mott, with advice from Dan Swinehart and other colleagues.
[1] The ideas and techniques were refined in the Apple Lisa and Macintosh and spread from there to most modern document preparation systems.
Although similar in capabilities to the then-current version of Bravo, the user interface of Gypsy was radically different.