Traits - The Next Generation.notes

TITLE OF PAPER: Traits - The Next Generation
URL OF PRESENTATION:
PRESENTED BY: David Morrill
REPRESENTING: Enthought

CONFERENCE: PyCon 2005
DATE: Wednesday, March 23, 2005
LOCATION: GWU Cafritz Conference Center, Marvin (Pressure Cooker) Theatre

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REAL-TIME NOTES / ANNOTATIONS OF THE PAPER:
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PyCon presentation two years ago
* Core Traits
* Spin off of Chaco project

This year we talk about the next generation

Traits History
    Traits 1: Mid 2002, spin-off from the Chaco project. Pure Python.
        Talk on Traits 1 presented at PyCon 2003
    Traits 2: mid 2004, Major rewrite, converted to "new style" Python types
        using a C-based extension module. Much faster with a streamlined syntax

Validation
    Every trait has an associated "type" or set of values that can be assigned
    Or the type can be very (psychotically) flexible
        Trait(0.0, Range(0.0, 1.0), Enum('low', 'middle', 'high'))
    Traits comes with a number of predefined types
        Constant,int, float..

Initialization
    Must have default value
    Does not require explicit consturtors

Delegation
    Traits can be delegated, on whole, or selectively
    The granularity of delegation is at a trait level
    Delegated traits use no space until assigned to

Notification
    Changed value triggers notification..

[Delegation Example]
    (rather un-pythonic syntax)

Notification
    Changes to a trait's value can trigger "notification handlers"
    Two types of notifications:
        normal - only triggers when the value changes
        event - triggers on every assignment (even if there's no change)
    Two types of notification handlers
        Static - defined in the class that defines the trait via naming conv
        Dynamic - using the on_trait_change(...) method
    Performance implications of notification?
    Is notification plugable?

Visualization
    User interfaces can be easily constructed for objects with traits
    Supports several different styles of UI
        Panel, subpanel, modal, nonmodal, livemodal, live, wizard
    Supports MVC paradigm
    Each trait has a default "editor" associated with it.
    There is a large set of predefined trait editors
        boolean, button, enum, font, tree, ...
    New editors can be defined
    Cross-platform, cross-GUI (sort of)
    Supports
        Automatic change history (undo/redo/etc.)
        Automatic and user-defined help screens
        Modal or "live" dialogs
        Menus, Toolbars
    Dynamic updates via event handlers

Implementation
    Traits 2 based on "new style" Python classes
    Core functionality in a C extension
    Initialization, validation, delegation, and notification all in C

Speed
    Traits faster than old/new style __gets__
    Puts between old/new style __puts__
    Notifications add a ton of (Python code) overhead to sets

VET (View Editing Tool)
    Interactive tool for creating traits-based user interfaces
    Automatically generates Python modules based on an MVC framework
    Somewhat different than a VB-style tool: you start with your Model and it
        helps you build the View and Controller.
    VET is itself a traits-based UI
    Still in development, but already useful

Status
    Traits is an Enthought core package, used by:
        Chaco (plotting)
        Enable (component framework)
        Envisage (Eclipse-like plug-in framework)
        Graph
        Pyface (wxPython model-based widgets)

    Fairly stable. Mostly tested on Win32, but some use on Linux
    To do:
        Add more editors (e.g. Table/List editor)
        More docs (currently 132+ pp.)
        Support more GUI toolkits (OS X?) (HTML? I'm guessing not, since the
            whole disableIf() thing would have to be totally rethought.)
            (he mentioned Tk as one currently supported GUI)
        Issue first release

Example code:
    The code is more "declarative" as in you don't write much code to do stuff
        but rather declare stuff to make stuff happen.

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REFERENCES: {as documents / sites are referenced add them below}

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CONTRIBUTORS: {add your name, e-mail address and URL below}
Nick Bastin (nick.bastin@gmail.com) <http://www.nickbastin.com>
Abhay Saxena <ark3@email.com>
Linden Wright <lwright@mac.com>
Andy Wright <waw@well.com>

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E-MAIL BOUNCEBACK: {add your e-mail address separated by commas }
Erik Rose <corp@grinchcentral.com>

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