[Imported from Trac: page TracWikiMacros, version 1]

TracWikiMacros.md

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+# Trac Macros
+
+[PageOutline](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](WikiFormatting).
+
+Another kind of macros are [WikiProcessors](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](TracPlugins). This gives them some capabilities that macros do not have, such as being able to directly access the HTTP request.
+
+### Example
+
+A list of 3 most recently changed wiki pages starting with 'Trac':
+
+```
+ [[RecentChanges(Trac,3)]]
+```
+
+Display:
+ [RecentChanges](RecentChanges)(Trac,3)
+
+## 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 [mod_python](TracModPython).*
+
+[MacroList](MacroList)
+
+## Macros from around the world
+
+The [Trac Hacks](http://trac-hacks.org/) site provides a wide collection of macros and other Trac [plugins](TracPlugins) 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 [Python programming language](http://python.org/).
+
+For more information about developing macros, see the [development resources](TracDev) on the main project site.
+
+
+## Implementation
+
+Here are 2 simple examples on how to create a Macro with [Trac 0.11](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 about the transition.
+
+### Macro without arguments
+It should be saved as `TimeStamp.py` as Trac will use the module name as the Macro name
+```#!python
+from datetime import datetime
+# Note: since Trac 0.11, datetime objects are used internally
+
+from genshi.builder import tag
+
+from trac.util.datefmt import format_datetime, utc
+from trac.wiki.macros import WikiMacroBase
+
+class TimestampMacro(WikiMacroBase):
+    """Inserts the current time (in seconds) into the wiki page."""
+
+    revision = "$Rev$"
+    url = "$URL$"
+
+    def expand_macro(self, formatter, name, args):
+        t = datetime.now(utc)
+        return tag.b(format_datetime(t, '%c'))
+```
+
+### 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
+```#!python
+from trac.wiki.macros import WikiMacroBase
+
+class HelloWorldMacro(WikiMacroBase):
+    """Simple HelloWorld macro.
+
+    Note that the name of the class is meaningful:
+     - it must end with "Macro"
+     - what comes before "Macro" ends up being the macro name
+
+    The documentation of the class (i.e. what you're reading)
+    will become the documentation of the macro, as shown by
+    the !MacroList macro (usually used in the TracWikiMacros page).
+    """
+
+    revision = "$Rev$"
+    url = "$URL$"
+
+    def expand_macro(self, formatter, name, args):
+        """Return some output that will be displayed in the Wiki content.
+
+        `name` is the actual name of the macro (no surprise, here it'll be
+        `'HelloWorld'`),
+        `args` is the text enclosed in parenthesis at the call of the macro.
+          Note that if there are ''no'' parenthesis (like in, e.g.
+          [[HelloWorld]]), then `args` is `None`.
+        """
+        return 'Hello World, args = ' + unicode(args)
+    
+    # Note that there's no need to HTML escape the returned data,
+    # as the template engine (Genshi) will do it for us.
+```
+
+
+### `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:
+
+```#!python
+  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())
+```