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""" The Envisage version of the old chestnut. """
# Standard library imports.
import logging
# Enthought library imports.
from enthought.envisage.api import Application, ExtensionPoint, Plugin
from enthought.traits.api import List, Str
# Create a log file.
logger = logging.getLogger()
logger.addHandler(logging.StreamHandler(file('hello_world.log', 'w')))
logger.setLevel(logging.DEBUG)
class HelloWorld(Plugin):
""" The 'Hello World' plugin.
This plugin offers a single extension point 'greetings' which is a list of
greetings, one of which is used to produce the '<greeting> World' message
when the plugin is started.
"""
# This tells us that the plugin offers the 'greetings' extension point,
# and that plugins that want to contribute to it must each provide a list
# of strings (Str).
greetings = ExtensionPoint(
List(Str), id='greetings', desc='Greetings for "Hello World"'
)
# Plugin's have two important lifecyle methods, 'start' and 'stop'. These
# methods are called automatically by Envisage when the application is
# started and stopped respectively.
def start(self):
""" Start the plugin. """
# Standard library imports.
#
# We put this import here just to emphasize that it is only used in
# this specific plugin.
import random
print random.choice(self.greetings), 'World!'
return
class Greetings(Plugin):
""" A plugin that contributes to the 'greetings' extension point. """
# This tells us that the plugin contributes the value of this trait to the
# 'greetings' extension point.
greetings = List(["Hello", "G'day"], contributes_to='greetings')
class MoreGreetings(Plugin):
""" Another plugin that contributes to the 'greetings' extension point. """
# This tells us that the plugin contributes the value of this trait to the
# 'greetings' extension point.
greetings = List(contributes_to='greetings')
# This shows how you can use a standard trait initializer to populate the
# list dynamically.
def _greetings_default(self):
""" Trait initializer. """
extensions = [
'The %s application says %s' % (self.application.id, greeting)
for greeting in ['Bonjour', 'Hola']
]
return extensions
# Application entry point.
if __name__ == '__main__':
# Create the application.
#
# An application is simply a collection of plugins. In this case we
# specify the plugins explicitly, but the mechanism for finding plugins
# is configurable by setting the application's 'plugin_manager' trait.
application = Application(
id='hello.world', plugins=[HelloWorld(), Greetings(), MoreGreetings()]
)
# Run it!
application.run()
#### EOF ######################################################################
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