Most of the commands in Pynsource are wrapped in command objects, which have
an **execute** , undo and redo method.
This is a classic use of the Command design pattern.
The main app class **MainApp** is different to the App class in Pynsource \-
containing the main GUI handlers.
It points to a `umlcanvas` which is where all the fancy drawing is done, using
the wxPython GUI toolkit.
Here are some screenshots of what's possible to dra…
The App class owns an instance of Controller. The App class also has a Boot()
method, as well as a Shutdown() method.
The Controller is defined thus:
def __init__(self, app):
self.app = app
self.cmd_mgr = CommandManager(100)