[[TOC]]

= Egg cooking =

Since Trac 0.11, Genshi is used as the new template engine.  Some APIs have also been changed.

This tutorial shows how to make an egg, and load an egg in Trac. In the advanced parts you'll learn how to serve templates and static content from an egg.

You should be familiar with [trac:TracDev/ComponentArchitecture component architecture] and [trac:TracDev/PluginDevelopment plugin development]. This plugin is based on the example in the plugin development article.  Here we extend it a bit further.

== Required items ==

 * ''setuptools>=0.6b1''. For instructions and files see [http://peak.telecommunity.com/DevCenter/EasyInstall#installing-easy-install EasyInstall] page.
 * '''Trac 0.11'''.  Download it from the [http://projects.edgewall.com/trac/wiki/TracDownload TracDownload] page.
 * '''Genshi>-0.4'''. Download it from the [http://genshi.edgewall.org/wiki/Download GenshiDownload] page.

== Directories ==

To develop a plugin you need to create a few directories to keep things together.

So let's create following directories:
{{{
./helloworld-plugin/
./helloworld-plugin/helloworld/
}}}

== Main plugin ==

The first step is to generate the main module for this plugin.  We will construct a simple plugin that will display "Hello world!" on the screen when accessed through the /helloworld URL. The plugin also provides a "Hello" button that is, by default, rendered on the far right in the main navigation bar.

So create ''helloworld.py'' in ''./helloworld-plugin/helloworld/'':
{{{
#!python
# Helloworld plugin

import re

from genshi.builder import tag

from trac.core import *
from trac.web import IRequestHandler
from trac.web.chrome import INavigationContributor

class HelloWorldPlugin(Component):
    implements(INavigationContributor, IRequestHandler)

    # INavigationContributor methods
    def get_active_navigation_item(self, req):
        return 'helloworld'
    
    def get_navigation_items(self, req):
        yield ('mainnav', 'helloworld',
               tag.a('Hello World', href=req.href.helloworld()))
    
    # IRequestHandler methods
    def match_request(self, req):
        return re.match(r'/helloworld(?:_trac)?(?:/.*)?$', req.path_info)
    
    def process_request(self, req):
        req.send_response(200)
        req.send_header('Content-Type', 'text/plain')
        req.end_headers()
        req.write('Hello world!')
}}}

To help understand how that works, read the [http://trac.edgewall.org/browser/trunk/trac/web/chrome.py#L108 INavigationContributor] and [http://trac.edgewall.org/browser/trunk/trac/web/api.py#L517 IRequestHandler] interface specifications.

== Make it a module ==

To make the plugin a module, you simply create an ''_''____''_init_''____''_.py'' in ''./helloworld-plugin/helloworld/'':
{{{
#!python
# Helloworld module
from helloworld import *
}}}

== Make it an egg ==

Now it's time to make it an egg. For that we need a chicken called ''setup.py'' in ''./helloworld-plugin/'':
{{{
#!python
from setuptools import find_packages, setup

# name can be any name.  This name will be used to create .egg file.
# name that is used in packages is the one that is used in the trac.ini file.
# use package name as entry_points
setup(
    name='Trachelloworld', version='1.1',
    packages=find_packages(exclude=['*.tests*']),
    entry_points = """
        [trac.plugins]
        helloworld = helloworld
    """,
)
}}}

You done need to add special [http://peak.telecommunity.com/DevCenter/EggFormats#project-metadata egg metadata] in Trac 0.11.

== First deployment ==

Now try to build the plugin. Run the command {{{python setup.py bdist_egg}}} in the directory where you created it. If everything went OK you should have a .egg file in ''./dist'' directory.
Copy this ''.egg'' file to ''/[your trac env]/plugins'' directory. 

During development you can run the command {{{python setup.py develop}}} in the directory where you created it.  This way you don't need to do it every time you change the code. Check [trac:TracDev/PluginDevelopment] for more deployment options.

Restart the trac server.  If you're using mod_python you have to restart Apache.

Now you should see ''Hello World'' link at far right in main navigation bar when accessing your site. Click it.

== Aftermath ==

Now you have successfully created your first egg. You can continue further to learn how to use templates in your plugins, and make its output look like other Trac pages.


[[TagIt(khundeen)]]