Trac Macros

Trac macros extend Trac with custom functionality. Macros are a special type of plugin and are written in Python. A macro generates HTML in any context supporting WikiFormatting.

The macro syntax is [[macro-name(optional-arguments)]].

WikiProcessors are another kind of macro, commonly used for source code highlighting using a processor like !#python or !#apache:

{{{#!wiki-processor-name
...
}}}

Using Macros

Macro calls are enclosed in double-square brackets [[..]]. Like Python functions macros can have arguments, which take the form of a comma separated list within parentheses [[..(,)]]. A common macro used is a list of the 3 most recent changes to a wiki page, or here, for example, all wiki pages starting with 'Trac':

Wiki Markup	Display
[[RecentChanges(Trac,3)]]	09/05/24 TracWorkflow (diff) TracUpgrade (diff) TracUnicode (diff)

Getting Detailed Help

The list of available macros and the full help can be obtained using the MacroList macro, see below.

A brief list can be obtained via [[MacroList(*)]] or [[?]].

Detailed help on a specific macro can be obtained by passing it as an argument to MacroList, e.g. [[MacroList(MacroList)]], or more conveniently, by appending a question mark (?) to the macro's name, like in [[MacroList?]].

Available Macros

[[AboutWikiBoxes]]

Display a wiki page on how to use boxes.

[[AboutWikiIcons]]

Display a wiki page on how to use icons.

[[AboutWikiPhrases]]

Display a wiki page on how to use attentional phrases.

[[Color]]

Decorate text with colors.

Syntax:

[[Color(text, fg/bg/size)]]

where

• text is the text to decorate. Enter a leading and/or trailing space character to surround the text with a decorated space.
• fg/bg/size defines the foreground and background colors, and a font size. All parameters are optional and separated by slash character (/).

Colors may be specified as an RGB triplet in hexadecimal format (a hex triplet; e.g. #000 or #000000 for black); they may also be specified according to their common English names (e.g. red, green, blue etc.). See ​here for details.

Examples:

[[Color(Large red on yellow, red/yellow/150%)]]
[[Color(Red on yellow, red/yellow)]]
[[Color(Yellow background, /yellow)]]
[[Color(Large red, #f00/2em)]]
[[Color(Large on yellow, /yellow/20px)]]
[[Color(Text, can, have, commas, /yellow)]]
[[Color( Surrounding space is also decorated , white/red)]]

To set the foreground color for a larger block, the processor variant can be used (background color and font size may not display as expected due to the mechanisms of cascading style sheets, be advised and use the color parameter only):

{{{#!Color color=green
...
}}}

[[CommitTicketReference]]

Insert a changeset message into the output.

This macro must be called using wiki processor syntax as follows:

{{{
#!CommitTicketReference repository="reponame" revision="rev"
}}}

where the arguments are the following:

• repository: the repository containing the changeset
• revision: the revision of the desired changeset

[[Icon]]

Shows a named icon that can be in line with text.

Syntax:

[[Icon(name, size)]]

where

• name is the name of the icon. When name contains a pattern character (* or ?), a 2-column preview of matching icons is presented, which should mainly be used for finding and selecting an icon during wiki page editing in side-by-side mode (however, no more than 32 icons are presented to prevent exhaustive network traffic.)
• size is optionally one of small, medium or large or an abbreviation thereof (defaults small).

Example:

[[Icon(smiley)]]

Use ShowIcons for static presentation of available icons. Smileys like :-) are automatically rendered as icons. Use ShowSmileys to se all available smileys.

Following wiki markup is equivalent to using this macro:

(|name, size|)

[[Image]]

Embed an image in wiki-formatted text.

The first argument is the file specification. The file specification may reference attachments in three ways:

• module:id:file, where module can be either wiki or ticket, to refer to the attachment named file of the specified wiki page or ticket.
• id:file: same as above, but id is either a ticket shorthand or a Wiki page name.
• file to refer to a local attachment named 'file'. This only works from within that wiki page or a ticket.

The file specification may also refer to:

• repository files, using the source:file syntax (source:file@rev works also).
• files, using direct URLs: /file for a project-relative, //file for a server-relative, or http://server/file for absolute location. An InterWiki prefix may be used.
• embedded data using the ​rfc2397 data URL scheme, provided the URL is enclosed in quotes.

The remaining arguments are optional and allow configuring the attributes and style of the rendered <img> element:

• digits and unit are interpreted as the size (ex. 120px, 25%) for the image
• right, left, center, top, bottom and middle are interpreted as the alignment for the image (alternatively, the first three can be specified using align=... and the last three using valign=...)
• link=some TracLinks... replaces the link to the image source by the one specified using a TracLinks. If no value is specified, the link is simply removed.
• inline specifies that the content generated be an inline XHTML element. By default, inline content is not generated, therefore images won't be rendered in section headings and other one-line content.
• nolink means without link to image source (deprecated, use link=)
• key=value style are interpreted as HTML attributes or CSS style indications for the image. Valid keys are:
  • align, valign, border, width, height, alt, title, longdesc, class, margin, margin-(left,right,top,bottom), id and usemap
  • border, margin, and margin-* can only be a single number (units are pixels).
  • margin is superseded by center which uses auto margins

Examples:

[[Image(photo.jpg)]]               # simplest
[[Image(photo.jpg, 120px)]]        # with image width size
[[Image(photo.jpg, right)]]        # aligned by keyword
[[Image(photo.jpg, nolink)]]       # without link to source
[[Image(photo.jpg, align=right)]]  # aligned by attribute

You can use an image from a wiki page, ticket or other module.

[[Image(OtherPage:foo.bmp)]]    # from a wiki page
[[Image(base/sub:bar.bmp)]]     # from hierarchical wiki page
[[Image(#3:baz.bmp)]]           # from another ticket
[[Image(ticket:36:boo.jpg)]]    # from another ticket (long form)
[[Image(source:/img/bee.jpg)]]  # from the repository
[[Image(htdocs:foo/bar.png)]]   # from project htdocs dir
[[Image(shared:foo/bar.png)]]   # from shared htdocs dir (since 1.0.2)

Adapted from the Image.py macro created by Shun-ichi Goto <gotoh@…>

[[InterTrac]]

Provide a list of known InterTrac prefixes.

[[InterWiki]]

Provide a description list for the known InterWiki prefixes.

[[KnownMimeTypes]]

List all known mime-types which can be used as WikiProcessors.

Can be given an optional argument which is interpreted as mime-type filter.

[[MacroList]]

Display a list of all installed Wiki macros, including documentation if available.

Optionally, the name of a specific macro can be provided as an argument. In that case, only the documentation for that macro will be rendered.

Note that this macro will not be able to display the documentation of macros if the PythonOptimize option is enabled for mod_python!

[[PageOutline]]

Display a structural outline of the current wiki page, each item in the outline being a link to the corresponding heading.

This macro accepts four optional parameters:

• The first is a number or range that allows configuring the minimum and maximum level of headings that should be included in the outline. For example, specifying "1" here will result in only the top-level headings being included in the outline. Specifying "2-3" will make the outline include all headings of level 2 and 3, as a nested list. The default is to include all heading levels.
• The second parameter can be used to specify a custom title (the default is no title).
• The third parameter selects the style of the outline. This can be either inline or pullout (the latter being the default). The inline style renders the outline as normal part of the content, while pullout causes the outline to be rendered in a box that is by default floated to the right side of the other content.
• The fourth parameter specifies whether the outline is numbered or not. It can be either numbered or unnumbered (the former being the default). This parameter only has an effect in inline style.

[[RecentChanges]]

List all pages that have recently been modified, ordered by the time they were last modified.

This macro accepts two ordered arguments and a named argument. The named argument can be placed in any position within the argument list.

The first parameter is a prefix string: if provided, only pages with names that start with the prefix are included in the resulting list. If this parameter is omitted, all pages are included in the list.

The second parameter is the maximum number of pages to include in the list.

The group parameter determines how the list is presented:

group=date

The pages are presented in bulleted lists that are grouped by date (default).

group=none

The pages are presented in a single bulleted list.

Tip: if you only want to specify a maximum number of entries and don't want to filter by prefix, specify an empty first parameter, e.g. [[RecentChanges(,10,group=none)]].

[[RepositoryIndex]]

Display the list of available repositories.

Can be given the following named arguments:

format

Select the rendering format:

• compact produces a comma-separated list of repository prefix names (default)
• list produces a description list of repository prefix names
• table produces a table view, similar to the one visible in the Browse View page

glob

Do a glob-style filtering on the repository names (defaults to '*')

order

Order repositories by the given column (one of "name", "date" or "author")

desc

When set to 1, order by descending order

[[ShowEntities]]

Renders in a table the list of HTML entities. Optional argument is the number of columns in the table (defaults 3).

[[ShowIcons]]

Renders in a table a list of available icons. No more than 96 icons are displayed to prevent exhaustive network traffic.

Syntax:

[[ShowIcons(cols, name-pattern, size, header, limit)]]

where

• cols is optionally the number of columns in the table (defaults 3).
• name-pattern selects which icons to list (use * and ?).
• size is optionally one of small, medium or large or an abbreviation thereof (defaults small).
• header is optionally one of header and noheader or an abbreviation thereof (header is displayed by default)
• limit specifies an optional upper limit of number of displayed icons (however, no more than 96 will be displayed).

The last three optional parameters (size, header and limit) can be stated in any order.

Example:

[[ShowIcons(smile*)]]              # all small icons matching smile*
[[ShowIcons(4, smile*)]]           # four columns
[[ShowIcons(smile*, 10)]]          # limit to 10 icons
[[ShowIcons(smile*, 10, nohead)]]  # no header
[[ShowIcons(smile*, m)]]           # medium-size

[[ShowPhrases]]

Renders in a table the list of known phrases that are highlighted to catch attention.

Comment: Any delimiter ():<> adjacent to a phrase will not be presented. This makes it possible to naturally write FIXME:, for example, but view the phrase highlighted without the colon (:) which would not look natural. Prefixing a phrase with ! prevents it from being highlighted.

[[ShowSmileys]]

Renders in a table the list of available smileys. Optional argument is the number of columns in the table (defaults 3).

Comment: Prefixing a character sequence with ! prevents it from being interpreted as a smiley.

[[ShowSymbols]]

Renders in a table the list of known symbols. Optional argument is the number of columns in the table (defaults 3).

[[SubscriberList]]

Display a list of all installed notification subscribers, including documentation if available.

Optionally, the name of a specific subscriber can be provided as an argument. In that case, only the documentation for that subscriber will be rendered.

Note that this macro will not be able to display the documentation of subscribers if the PythonOptimize option is enabled for mod_python!

[[TOC]]

Generate a table of contents for the current page or a set of pages.

If no arguments are given, a table of contents is generated for the current page, with the top-level title stripped:

[[TOC]]

To generate a table of contents for a set of pages, simply pass them as comma separated arguments to the TOC macro, e.g. as in

[[TOC(TracGuide, TracInstall, TracUpgrade, TracIni, TracAdmin, TracBackup,
      TracLogging, TracPermissions, TracWiki, WikiFormatting, TracBrowser,
      TracRoadmap, TracChangeset, TracTickets, TracReports, TracQuery,
      TracTimeline, TracRss, TracNotification)]]

A wildcard * can be used to fetch a sorted list of all pages starting with the preceding pagename stub:

[[TOC(Trac*, WikiFormatting, WikiMacros)]]

The following control arguments change the default behaviour of the TOC macro:

Argument	Description
heading=<x>	Override the default heading of "Table of Contents"
noheading	Suppress display of the heading.
depth=<n>	Display headings of subsequent pages to a maximum depth of <n>.
inline	Display TOC inline rather than as a side-bar.
sectionindex	Only display the page name and title of each page in the wiki section.
titleindex	Only display the page name and title of each page, similar to TitleIndex.
notitle	Supress display of page title.
reverse	Display TOC sorted in reversed order. (Since 11.0.0.4)
from=page	Obtain the list of pages to show from the content (one page name per line) of another wiki page.
nonumbering	Suppress automatic numbering for inline TOC (Since 11.0.0.7)

For titleindex argument, an empty pagelist will evaluate to all pages:

[[TOC(titleindex, notitle, heading=All pages)]]

The sectionindex argument allows a title index to be generated for all pages in a given section of the wiki. A section is defined by wiki page name, using / as a section level delimiter (like directories in a file system). Giving / or * as the page name produces the same result as titleindex (title of all pages). If a page name ends with a /, only children of this page will be processed. Otherwise, the page given in the argument is also included, if it exists. For sectionindex argument, an empty pagelist will evaluate to all page below the same parent as the current page:

[[TOC(sectionindex, notitle, heading=This section pages)]]

The 'from' option allows you to read the lines of content from another wiki page and use that as the pagelist for the table of contents. The page names listed there are processed as if they are named in the TOC macro (start a line with a # to treat it as a comment). If the wiki page TOC/Guide contains

TracGuide
TracInstall
TracReports/Active

then these two calls to TOC are equivalent:

[[TOC(from=TOC/Guide)]]
[[TOC(TracGuide, TracInstall, TracReports/Active)]]

However, updating page TOC/Guide changes the TOC in all places that use from= to refer to it. This can be useful instead of custom macros like [[TracGuideToc]].

[[TicketQuery]]

Wiki macro listing tickets that match certain criteria.

This macro accepts a comma-separated list of keyed parameters, in the form "key=value".

If the key is the name of a field, the value must use the syntax of a filter specifier as defined in TracQuery#QueryLanguage. Note that this is not the same as the simplified URL syntax used for query: links starting with a ? character. Commas (,) can be included in field values by escaping them with a backslash (\).

Groups of field constraints to be OR-ed together can be separated by a literal or argument.

In addition to filters, several other named parameters can be used to control how the results are presented. All of them are optional.

The format parameter determines how the list of tickets is presented:

• list — the default presentation is to list the ticket ID next to the summary, with each ticket on a separate line.
• compact — the tickets are presented as a comma-separated list of ticket IDs.
• count — only the count of matching tickets is displayed
• rawcount — only the count of matching tickets is displayed, not even with a link to the corresponding query (since 1.1.1)
• table — a view similar to the custom query view (but without the controls)
• progress — a view similar to the milestone progress bars

The max parameter can be used to limit the number of tickets shown (defaults to 0, i.e. no maximum).

The order parameter sets the field used for ordering tickets (defaults to id).

The desc parameter indicates whether the order of the tickets should be reversed (defaults to false).

The group parameter sets the field used for grouping tickets (defaults to not being set).

The groupdesc parameter indicates whether the natural display order of the groups should be reversed (defaults to false).

The verbose parameter can be set to a true value in order to get the description for the listed tickets. For table format only. deprecated in favor of the rows parameter

The rows parameter can be used to specify which field(s) should be viewed as a row, e.g. rows=description|summary

The col parameter can be used to specify which fields should be viewed as columns. For table format only.

For compatibility with Trac 0.10, if there's a last positional parameter given to the macro, it will be used to specify the format. Also, using "&" as a field separator still works (except for order) but is deprecated.

[[TitleIndex]]

Insert an alphabetic list of all wiki pages into the output.

Accepts a prefix string as parameter: if provided, only pages with names that start with the prefix are included in the resulting list. If this parameter is omitted, all pages are listed. If the prefix is specified, a second argument of value hideprefix can be given as well, in order to remove that prefix from the output.

The prefix string supports the standard relative-path notation when using the macro in a wiki page. A prefix string starting with ./ will be relative to the current page, and parent pages can be specified using ../.

Several named parameters can be specified:

• format=compact: The pages are displayed as comma-separated links.
• format=group: The list of pages will be structured in groups according to common prefix. This format also supports a min=n argument, where n is the minimal number of pages for a group.
• format=hierarchy: The list of pages will be structured according to the page name path hierarchy. This format also supports a min=n argument, where higher n flatten the display hierarchy
• depth=n: limit the depth of the pages to list. If set to 0, only toplevel pages will be shown, if set to 1, only immediate children pages will be shown, etc. If not set, or set to -1, all pages in the hierarchy will be shown.
• include=page1:page*2: include only pages that match an item in the colon-separated list of pages. If the list is empty, or if no include argument is given, include all pages.
• exclude=page1:page*2: exclude pages that match an item in the colon- separated list of pages.

The include and exclude lists accept shell-style patterns.

[[TracAdminHelp]]

Display help for trac-admin commands.

Examples:

[[TracAdminHelp]]               # all commands
[[TracAdminHelp(wiki)]]         # all wiki commands
[[TracAdminHelp(wiki export)]]  # the "wiki export" command
[[TracAdminHelp(upgrade)]]      # the upgrade command

[[TracGuideToc]]

Display a table of content for the Trac guide.

This macro shows a quick and dirty way to make a table-of-contents for the Help/Guide. The table of contents will contain the Trac* and WikiFormatting pages, and can't be customized. See the ​TocMacro for a more customizable table of contents.

[[TracIni]]

Produce documentation for the Trac configuration file.

Typically, this will be used in the TracIni page. The macro accepts two ordered arguments and two named arguments.

The ordered arguments are a configuration section filter, and a configuration option name filter: only the configuration options whose section and name start with the filters are output.

The named arguments can be specified:

section

a glob-style filtering on the section names

option

a glob-style filtering on the option names

[[Workflow]]

Render a workflow graph.

This macro accepts a TracWorkflow configuration and renders the states and transitions as a directed graph. If no parameters are given, the current ticket workflow is rendered.

In WikiProcessor mode the width and height arguments can be specified (Defaults: width = 800 and height = 600).

The repository-scoped path of a workflow file can be specified as either a macro or WikiProcessor file argument. The file revision can be specified by appending @<rev> to the path. The file argument value must be enclosed in single or double quotes. (Since 1.3.2).

Examples:

[[Workflow()]]

[[Workflow(go = here -> there; return = there -> here)]]

[[Workflow(file=/contrib/workflow/enterprise-workflow.ini@1)]]

{{{#!Workflow file="/contrib/workflow/enterprise-workflow.ini"
}}}

{{{#!Workflow width=700 height=700
leave = * -> *
leave.operations = leave_status
leave.default = 1

create = <none> -> new
create.default = 1

create_and_assign = <none> -> assigned
create_and_assign.label = assign
create_and_assign.permissions = TICKET_MODIFY
create_and_assign.operations = may_set_owner

accept = new,assigned,accepted,reopened -> accepted
accept.permissions = TICKET_MODIFY
accept.operations = set_owner_to_self

resolve = new,assigned,accepted,reopened -> closed
resolve.permissions = TICKET_MODIFY
resolve.operations = set_resolution

reassign = new,assigned,accepted,reopened -> assigned
reassign.permissions = TICKET_MODIFY
reassign.operations = set_owner

reopen = closed -> reopened
reopen.permissions = TICKET_CREATE
reopen.operations = del_resolution
}}}

[[box]]

View wiki text in a box.

Syntax:

{{{#!box type align=... width=...
wiki text
}}}

or preferably when content is short:

[[box(wiki text, type=..., align=..., width=...)]]

where

• type is an optional flag, or parameter, to call for attention depending on type of matter. When type is set, the box is decorated with an icon (except for news) and colored, depending on what urgency the type represents:

Urgency (box color)	type
warn (red)	bug, critical, error, important, stop, warning
highlight (yellow)	help, information, note, question, tips
elaborate (blue)	bad, chat, comment, discussion, good, no, nok, ok, talk, yes
news (green)	news
normal (white)	configuration, configure, details, look, magnifier, tool

type may be abbreviated as long as the abbreviation is unique for one of the keywords above.

• align is optionally one of right, left or center. The rbox macro is an alias for align=right.
• width is optional and sets the width of the box (defaults auto except for right aligned boxes which defaults a fixed width). width should be set when align=center for proper results.

Examples:

{{{#!box warn
= Warning
Beware of the bugs
}}}

[[box(Beware of the bugs, type=warn)]]

A style parameter is also accepted, to allow for custom styling of the box. See also the rbox, newsbox and imagebox macros (processors).

[[imagebox]]

Present a centered box suitable for one image.

Syntax:

{{{#!imagebox
wiki text
}}}

This box is typically used together with the Image macro:

{{{#!imagebox
[[Image(file)]]

Caption
}}}

Note that the size parameter of the Image macro may not behave as expected when using relative sizes (%).

The following parameters are also accepted:

• align — One of right, left or center (defaults center).
• width — Set the width of the box (defaults auto except for right aligned boxes which defaults a fixed width).
• style — Custom styling of the box.

See also the box, rbox and newsbox macros (processors).

[[lbox]]

View a left-aligned box. (This is a shorthand for box align=left)

Syntax:

{{{#!lbox type width=...
wiki text
}}}

or preferably when content is short:

[[lbox(wiki text, type=..., width=...)]]

where

• type is an optional flag, or parameter, to call for attention depending on type of matter. When type is set, the box is decorated with an icon (except for news) and colored, depending on what urgency the type represents:

Urgency (box color)	type
warn (red)	bug, critical, error, important, stop, warning
highlight (yellow)	help, information, note, question, tips
elaborate (blue)	bad, chat, comment, discussion, good, no, nok, ok, talk, yes
news (green)	news
normal (white)	configuration, configure, details, look, magnifier, tool

type may be abbreviated as long as the abbreviation is unique for one of the keywords above.

• width is optional and sets the width of the box (defaults a fixed width). Use width=auto for an automatically sized box.

Examples:

{{{#!lbox warn
= Warning
Beware of the bugs
}}}

[[lbox(Beware of the bugs, type=warn)]]

A style parameter is also accepted, to allow for custom styling of the box. See also the box, newsbox and imagebox macros (processors).

[[newsbox]]

Present a news box to the right. (This is a shorthand for rbox news)

Syntax:

{{{#!newsbox
wiki text
}}}

The following parameters are also accepted:

• width — Set the width of the box (defaults a fixed width).
• style — Custom styling of the box.

See also the box, rbox and imagebox macros (processors). (Comment: This box corresponds to the well-known NewsFlash macro.)

[[rbox]]

View a right-aligned box. (This is a shorthand for box align=right)

Syntax:

{{{#!rbox type width=...
wiki text
}}}

or preferably when content is short:

[[rbox(wiki text, type=..., width=...)]]

where

• type is an optional flag, or parameter, to call for attention depending on type of matter. When type is set, the box is decorated with an icon (except for news) and colored, depending on what urgency the type represents:

Urgency (box color)	type
warn (red)	bug, critical, error, important, stop, warning
highlight (yellow)	help, information, note, question, tips
elaborate (blue)	bad, chat, comment, discussion, good, no, nok, ok, talk, yes
news (green)	news
normal (white)	configuration, configure, details, look, magnifier, tool

type may be abbreviated as long as the abbreviation is unique for one of the keywords above.

• width is optional and sets the width of the box (defaults a fixed width). Use width=auto for an automatically sized box.

Examples:

{{{#!rbox warn
= Warning
Beware of the bugs
}}}

[[rbox(Beware of the bugs, type=warn)]]

A style parameter is also accepted, to allow for custom styling of the box. See also the box, newsbox and imagebox macros (processors).

Contributed macros

The ​Trac Hacks site provides a large collection of macros and other Trac plugins contributed by the Trac community. If you are looking for new macros, or have written one that you would like to share, please visit that site.

Developing Custom Macros

Macros, like Trac itself, are written in the ​Python programming language and are a type of plugin.

Here are 2 simple examples showing how to create a Macro. For more information about developing macros, see the ​development resources and ​sample-plugins.

Macro without arguments

To test the following code, copy it to timestamp_sample.py in the TracEnvironment's plugins/ directory.

from trac.util.datefmt import datetime_now, format_datetime, utc
from trac.util.html import tag
from trac.wiki.macros import WikiMacroBase

class TimestampMacro(WikiMacroBase):
    _description = "Inserts the current time (in seconds) into the wiki page."

    def expand_macro(self, formatter, name, content, args=None):
        t = datetime_now(utc)
        return tag.strong(format_datetime(t, '%c'))

Macro with arguments

To test the following code, copy it to helloworld_sample.py in the TracEnvironment's plugins/ directory.

from trac.util.translation import cleandoc_
from trac.wiki.macros import WikiMacroBase

class HelloWorldMacro(WikiMacroBase):
    _description = cleandoc_(
    """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 WikiMacros page).
    """)

    def expand_macro(self, formatter, name, content, args=None):
        """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'`),
        `content` 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 `content` is `None`.
        `args` will contain a dictionary of arguments when called using the
          Wiki processor syntax and will be `None` if called using the
          macro syntax.
        """
        return 'Hello World, content = ' + unicode(content)

Note that expand_macro optionally takes a 4^th parameter args. When the macro is called as a WikiProcessor, it is also possible to pass key=value processor parameters. If given, those are stored in a dictionary and passed in this extra args parameter. When called as a macro, args is None.

For example, when writing:

{{{#!HelloWorld style="polite" -silent verbose
<Hello World!>
}}}

{{{#!HelloWorld
<Hello World!>
}}}

[[HelloWorld(<Hello World!>)]]

One should get:

Hello World, text = <Hello World!>, args = {'style': u'polite', 'silent': False, 'verbose': True}
Hello World, text = <Hello World!>, args = {}
Hello World, text = <Hello World!>, args = None

Note that the return value of expand_macro is not HTML escaped. Depending on the expected result, you should escape it yourself (using return Markup.escape(result)), or if this is indeed HTML, wrap it in a Markup object: return Markup(result) (from trac.util.html import Markup).

You can also recursively use a wiki formatter to process the content as wiki markup:

from trac.wiki.formatter import format_to_html
from trac.wiki.macros import WikiMacroBase

class HelloWorldMacro(WikiMacroBase):
    def expand_macro(self, formatter, name, content, args):
        content = "any '''wiki''' markup you want, even containing other macros"
        # Convert Wiki markup to HTML
        return format_to_html(self.env, formatter.context, content)