= Trac Macros =

[[PageOutline]]

Trac macros are plugins to extend the Trac engine with custom 'functions' written in Python. A macro inserts dynamic HTML data in any context supporting WikiFormatting.

Another kind of macros are WikiProcessors. They typically deal with alternate markup formats and representation of larger blocks of information (like source code highlighting).

== Using Macros ==
Macro calls are enclosed in two ''square brackets''. Like Python functions, macros can also have arguments, a comma separated list within parentheses. 

Trac macros can also be written as TracPlugins. This gives them some capabilities that macros do not have, such as being able to directly access the HTTP request.

=== Examples ===

{{{
 [[Timestamp]]
}}}
Display:
 [[Timestamp]]

{{{
 [[HelloWorld(Testing)]]
}}}
Display:
 [[HelloWorld(Testing)]]

== Available Macros ==

''Note that the following list will only contain the macro documentation if you've not enabled `-OO` optimizations, or not set the `PythonOptimize` option for [wiki:TracModPython mod_python].''

[[MacroList]]

== Macros from around the world ==

The [http://trac-hacks.org/ Trac Hacks] site provides a wide collection of macros and other Trac [TracPlugins plugins] contributed by the Trac community. If you're looking for new macros, or have written one that you'd like to share with the world, please don't hesitate to visit that site.

== Developing Custom Macros ==
Macros, like Trac itself, are written in the [http://python.org/ Python programming language].

For more information about developing macros, see the [wiki:TracDev development resources] on the main project site.


== Implementation ==

Here are 2 simple examples on how to create a Macro with [wiki:0.11 Trac 0.11] have a look at source:trunk/sample-plugins/Timestamp.py for an example that shows the difference between old style and new style macros and also source:trunk/wiki-macros/README which Provides a little more insight.

=== Macro without arguments ===
It should be saved as `TimeStamp.py` as Trac will use the module name as the Macro name
{{{
from trac.core import *
from trac.wiki.macros import WikiMacroBase
from StringIO import StringIO
import time

__all__ = ['TimestampMacro']

class TimestampMacro(WikiMacroBase):
        """
        Macro for inserting timestamp

        {{{
        [[Timestamp]]
        }}}
        """
        def expand_macro(self, formatter, name, args):
                buf = StringIO()
                t = time.localtime()
                buf = "<b>%s</b>" % time.strftime('%c', t)
                return buf
}}}

=== Macro with arguments ===
It should be saved as `HelloWorld.py` (in the plugins/ directory) as Trac will use the module name as the Macro name
{{{
"""Example macro."""
from trac.core import *
from trac.wiki.macros import WikiMacroBase
from trac.util import escape

__all__ = ['HelloWorldMacro']

class HelloWorldMacro(WikiMacroBase):
        """
        Demo macro for a greeting with an argument.

        {{{
        [[HelloWorld(args)]]
        }}}

        """
        def expand_macro(self, formatter, name, args):
                # args will be `None` if the macro is called without parenthesis.
                txt = args or 'No arguments'

                # then, as `txt` comes from the user, it's important to guard against
                # the possibility to inject malicious HTML/Javascript, by using `escape()`:
                return 'Hello World, args = ' + escape(txt)
}}}


=== {{{expand_macro}}} details ===
{{{expand_macro}}} should return either a simple Python string which will be interpreted as HTML, or preferably a Markup object (use {{{from trac.util.html import Markup}}}).  {{{Markup(string)}}} just annotates the string so the renderer will render the HTML string as-is with no escaping.

If your macro creates wiki markup instead of HTML, you can convert it to HTML like this:

{{{
  text = "whatever wiki markup you want, even containing other macros"
  # Convert Wiki markup to HTML, new style
  out = StringIO()
  Formatter(formatter.context).format(text, out)
  return Markup(out.getvalue())
}}}