PyCon 2005 Submission
---------------------

Author:	   Martin Chilvers

Address:   Enthought Inc
	   515 Congress Ave Suite #1614
	   Austin TX 78701

E-mail:    martin@enthought.com
	   
Telephone: 512-536-1057
	   
Timeslot:  45 mins
	
Title:	   Envisage - An Extensible Application Framework
	   (An exercise in applied plagiarism)


Summary
-------

The Java world has two dominant frameworks for extensible application
development: Netbeans and Eclipse.  Although many people think of these two
projects as IDEs, they are both built upon open architectures that are designed
to support generic GUI application development.  Treading lightly in the
footsteps of these two excellent projects, Envisage attempts to bring similar
capabilities to the Python community.

The heart of Envisage is its plug-in architecture; in fact, the Envisage core
is little more than a system for discovering, loading, starting and stopping
plug-ins.  Developers construct applications by choosing from the set of
supplied plug-ins (possibly the empty set) and then adding their own to provide
domain-specific functionality.  Although an Envisage application need not have
a GUI, Envisage comes with an ever-expanding set of plug-ins that simplify many
of the more common and tedious aspects of GUI development (e.g., window
management, menubars/toolbars, user preferences). It is worth noting that these
'standard' plug-ins are written in exactly the same way as those written by an
application developer.  Each plug-in uses the Envisage extension mechanism not
only to contribute to what came before it, but also to define how future
plug-ins can contribute to it.  This mechanism is simple but consistent, and
ensures that even extensions to an application are extensible.

Despite the fact that development is still in its early stages (especially when
compared to the enormous effort that has gone into both Netbeans and Eclipse),
Envisage has already been used to deliver production applications, with two
more scheduled in the first half of this year.

This presentation will introduce the Envisage plug-in architecture, and
demonstrate how applications both with and without GUIs can be built with it.

Comments
--------

- Envisage is Open Source and will be released under some kind of BSD-style license.

- Envisage itself requires no GUI toolkit.  However the default UI plugin is written using two other Enthought packages (alos Open Source/BSD) 'traits' and 'pyface' that are specifically designed to support multiple toolkit back-ends.  We have the wx versions up and running and the tk versions in the works.

Presentation Outline
--------------------

1. Introduction

1.1 What Is Envisage?
    - Heritage
      - Eclipse
      - Netbeans
    - The different faces of Envisage
      - framework for extensible application development
      - framework for GUI application development
      - framework for scientific application development

2. Framework for Extensible Application Development

2.1 Goals
    - Extensible
    - Scaleable

2.2 The Envisage core
    - ~1000 lines of pure Python (1/4 of which are comments)
    - the application as a plug-in container
    - plug-in lifecycle management
      - discovery/load
      - start/stop
    - common services
      - extension registry
      - import management

2.3 Plug-ins
    - Extension mechanism
      - Python instead of XML
        - Typed definitions using Traits
      - Extension points
      - Extensions (contributions to extension points)

3. Framework for GUI application development
    - Common UI abstractions
      - actions
      - views
      - editors

4. Framework for scientific application development
    - Resource plug-in
      - extensible data types
      - persistence
    - Plotting
      - Chaco
    - Python Shell
    - 3-D visulaization
    - Materials DB

5. Future Work
   - a Python IDE?

---- EOF ----------------------------------------------------------------------