Trac Macros

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

The WikiProcessors are another kind of macros. They typically deal with alternate markup formats and transformation of larger "blocks" of information (like source code highlighting). They are used for processing the multiline {{{#!wiki-processor-name ... }}} blocks.

Using Macros

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

Getting Detailed Help

The list of available macros and the full help can be obtained using the MacroList macro, as seen 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?]].

Example

A list of 3 most recently changed wiki pages starting with 'Trac':

Wiki Markup	Display
[[RecentChanges(Trac,3)]]	Feb 26, 2013 TracStandalone (diff) TracInterfaceCustomization (diff) TracUpgrade (diff)
[[RecentChanges?(Trac,3)]]	[[RecentChanges]] L i s t a l l p a g e s t h a t h a v e r e c e n t l y b e e n m o d i f i e d , o r d e r e d b y t h e t i m e t h e y w e r e l a s t m o d i f i e d . T h i s m a c r o a c c e p t s t w o o r d e r e d a r g u m e n t s a n d a n a m e d a r g u m e n t . T h e n a m e d a r g u m e n t c a n b e p l a c e d i n a n y p o s i t i o n w i t h i n t h e a r g u m e n t l i s t . T h e f i r s t p a r a m e t e r i s a p r e f i x s t r i n g : i f p r o v i d e d , o n l y p a g e s w i t h n a m e s t h a t s t a r t w i t h t h e p r e f i x a r e i n c l u d e d i n t h e r e s u l t i n g l i s t . I f t h i s p a r a m e t e r i s o m i t t e d , a l l p a g e s a r e i n c l u d e d i n t h e l i s t . T h e s e c o n d p a r a m e t e r i s t h e m a x i m u m n u m b e r o f p a g e s t o i n c l u d e i n t h e l i s t . T h e ` g r o u p ` p a r a m e t e r d e t e r m i n e s h o w t h e l i s t i s p r e s e n t e d : ` g r o u p = d a t e ` : : T h e p a g e s a r e p r e s e n t e d i n b u l l e t e d l i s t s t h a t a r e g r o u p e d b y d a t e ( d e f a u l t ) . ` g r o u p = n o n e ` : : T h e p a g e s a r e p r e s e n t e d i n a s i n g l e b u l l e t e d l i s t . T i p : i f y o u o n l y w a n t t o s p e c i f y a m a x i m u m n u m b e r o f e n t r i e s a n d d o n ' t w a n t t o f i l t e r b y p r e f i x , s p e c i f y a n e m p t y f i r s t p a r a m e t e r , e . g . ` [ [ R e c e n t C h a n g e s ( , 1 0 , g r o u p = n o n e ) ] ] ` .
[[?]]	[[Image]] Embed an image in wiki-formatted text. The first argument is the file … [[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 … etc.

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.

[[CommitTicketReference]]

I n s e r t a c h a n g e s e t m e s s a g e i n t o t h e o u t p u t . T h i s m a c r o m u s t b e c a l l e d u s i n g w i k i p r o c e s s o r s y n t a x a s f o l l o w s : { { { { { { # ! C o m m i t T i c k e t R e f e r e n c e r e p o s i t o r y = " r e p o n a m e " r e v i s i o n = " r e v " } } } } } } w h e r e t h e a r g u m e n t s a r e t h e f o l l o w i n g : - ` r e p o s i t o r y ` : t h e r e p o s i t o r y c o n t a i n i n g t h e c h a n g e s e t - ` r e v i s i o n ` : t h e r e v i s i o n o f t h e d e s i r e d c h a n g e s e t

[[Image]]

E m b e d a n i m a g e i n w i k i - f o r m a t t e d t e x t . T h e f i r s t a r g u m e n t i s t h e f i l e s p e c i f i c a t i o n . T h e f i l e s p e c i f i c a t i o n m a y r e f e r e n c e a t t a c h m e n t s i n t h r e e w a y s : * ` m o d u l e : i d : f i l e ` , w h e r e m o d u l e c a n b e e i t h e r ' ' ' w i k i ' ' ' o r ' ' ' t i c k e t ' ' ' , t o r e f e r t o t h e a t t a c h m e n t n a m e d ' ' f i l e ' ' o f t h e s p e c i f i e d w i k i p a g e o r t i c k e t . * ` i d : f i l e ` : s a m e a s a b o v e , b u t i d i s e i t h e r a t i c k e t s h o r t h a n d o r a W i k i p a g e n a m e . * ` f i l e ` t o r e f e r t o a l o c a l a t t a c h m e n t n a m e d ' f i l e ' . T h i s o n l y w o r k s f r o m w i t h i n t h a t w i k i p a g e o r a t i c k e t . A l s o , t h e f i l e s p e c i f i c a t i o n m a y r e f e r t o r e p o s i t o r y f i l e s , u s i n g t h e ` s o u r c e : f i l e ` s y n t a x ( ` s o u r c e : f i l e @ r e v ` w o r k s a l s o ) . F i l e s c a n a l s o b e a c c e s s e d w i t h a d i r e c t U R L s ; ` / f i l e ` f o r a p r o j e c t - r e l a t i v e , ` / / f i l e ` f o r a s e r v e r - r e l a t i v e , o r ` h t t p : / / s e r v e r / f i l e ` f o r a b s o l u t e l o c a t i o n o f t h e f i l e . T h e r e m a i n i n g a r g u m e n t s a r e o p t i o n a l a n d a l l o w c o n f i g u r i n g t h e a t t r i b u t e s a n d s t y l e o f t h e r e n d e r e d ` < i m g

` e l e m e n t : * d i g i t s a n d u n i t a r e i n t e r p r e t e d a s t h e s i z e ( e x . 1 2 0 , 2 5 % ) f o r t h e i m a g e * ` r i g h t ` , ` l e f t ` , ` c e n t e r ` , ` t o p ` , ` b o t t o m ` a n d ` m i d d l e ` a r e i n t e r p r e t e d a s t h e a l i g n m e n t f o r t h e i m a g e ( a l t e r n a t i v e l y , t h e f i r s t t h r e e c a n b e s p e c i f i e d u s i n g ` a l i g n = . . . ` a n d t h e l a s t t h r e e u s i n g ` v a l i g n = . . . ` ) * ` l i n k = s o m e T r a c L i n k s . . . ` r e p l a c e s t h e l i n k t o t h e i m a g e s o u r c e b y t h e o n e s p e c i f i e d u s i n g a T r a c L i n k s . I f n o v a l u e i s s p e c i f i e d , t h e l i n k i s s i m p l y r e m o v e d . * ` n o l i n k ` m e a n s w i t h o u t l i n k t o i m a g e s o u r c e ( d e p r e c a t e d , u s e ` l i n k = ` ) * ` k e y = v a l u e ` s t y l e a r e i n t e r p r e t e d a s H T M L a t t r i b u t e s o r C S S s t y l e i n d i c a t i o n s f o r t h e i m a g e . V a l i d k e y s a r e : * a l i g n , v a l i g n , b o r d e r , w i d t h , h e i g h t , a l t , t i t l e , l o n g d e s c , c l a s s , m a r g i n , m a r g i n - ( l e f t , r i g h t , t o p , b o t t o m ) , i d a n d u s e m a p * ` b o r d e r ` , ` m a r g i n ` , a n d ` m a r g i n - ` * c a n o n l y b e a s i n g l e n u m b e r * ` m a r g i n ` i s s u p e r s e d e d b y ` c e n t e r ` w h i c h u s e s a u t o m a r g i n s E x a m p l e s : { { { [ [ I m a g e ( p h o t o . j p g ) ] ] # s i m p l e s t [ [ I m a g e ( p h o t o . j p g , 1 2 0 p x ) ] ] # w i t h i m a g e w i d t h s i z e [ [ I m a g e ( p h o t o . j p g , r i g h t ) ] ] # a l i g n e d b y k e y w o r d [ [ I m a g e ( p h o t o . j p g , n o l i n k ) ] ] # w i t h o u t l i n k t o s o u r c e [ [ I m a g e ( p h o t o . j p g , a l i g n = r i g h t ) ] ] # a l i g n e d b y a t t r i b u t e } } } Y o u c a n u s e i m a g e f r o m o t h e r p a g e , o t h e r t i c k e t o r o t h e r m o d u l e . { { { [ [ I m a g e ( O t h e r P a g e : f o o . b m p ) ] ] # i f c u r r e n t m o d u l e i s w i k i [ [ I m a g e ( b a s e / s u b : b a r . b m p ) ] ] # f r o m h i e r a r c h i c a l w i k i p a g e [ [ I m a g e ( # 3 : b a z . b m p ) ] ] # i f i n a t i c k e t , p o i n t t o # 3 [ [ I m a g e ( t i c k e t : 3 6 : b o o . j p g ) ] ] [ [ I m a g e ( s o u r c e : / i m a g e s / b e e . j p g ) ] ] # s t r a i g h t f r o m t h e r e p o s i t o r y ! [ [ I m a g e ( h t d o c s : f o o / b a r . p n g ) ] ] # i m a g e f i l e i n p r o j e c t h t d o c s d i r . } } } ' ' A d a p t e d f r o m t h e I m a g e . p y m a c r o c r e a t e d b y S h u n - i c h i G o t o < g o t o h @ t a i y o . c o . j p

' '

[[InterTrac]]

P r o v i d e a l i s t o f k n o w n I n t e r T r a c p r e f i x e s .

[[InterWiki]]

P r o v i d e a d e s c r i p t i o n l i s t f o r t h e k n o w n I n t e r W i k i p r e f i x e s .

[[KnownMimeTypes]]

L i s t a l l k n o w n m i m e - t y p e s w h i c h c a n b e u s e d a s W i k i P r o c e s s o r s . C a n b e g i v e n a n o p t i o n a l a r g u m e n t w h i c h i s i n t e r p r e t e d a s m i m e - t y p e f i l t e r .

[[MacroList]]

D i s p l a y a l i s t o f a l l i n s t a l l e d W i k i m a c r o s , i n c l u d i n g d o c u m e n t a t i o n i f a v a i l a b l e . O p t i o n a l l y , t h e n a m e o f a s p e c i f i c m a c r o c a n b e p r o v i d e d a s a n a r g u m e n t . I n t h a t c a s e , o n l y t h e d o c u m e n t a t i o n f o r t h a t m a c r o w i l l b e r e n d e r e d . N o t e t h a t t h i s m a c r o w i l l n o t b e a b l e t o d i s p l a y t h e d o c u m e n t a t i o n o f m a c r o s i f t h e ` P y t h o n O p t i m i z e ` o p t i o n i s e n a b l e d f o r m o d _ p y t h o n !

[[PageOutline]]

D i s p l a y a s t r u c t u r a l o u t l i n e o f t h e c u r r e n t w i k i p a g e , e a c h i t e m i n t h e o u t l i n e b e i n g a l i n k t o t h e c o r r e s p o n d i n g h e a d i n g . T h i s m a c r o a c c e p t s f o u r o p t i o n a l p a r a m e t e r s : * T h e f i r s t i s a n u m b e r o r r a n g e t h a t a l l o w s c o n f i g u r i n g t h e m i n i m u m a n d m a x i m u m l e v e l o f h e a d i n g s t h a t s h o u l d b e i n c l u d e d i n t h e o u t l i n e . F o r e x a m p l e , s p e c i f y i n g " 1 " h e r e w i l l r e s u l t i n o n l y t h e t o p - l e v e l h e a d i n g s b e i n g i n c l u d e d i n t h e o u t l i n e . S p e c i f y i n g " 2 - 3 " w i l l m a k e t h e o u t l i n e i n c l u d e a l l h e a d i n g s o f l e v e l 2 a n d 3 , a s a n e s t e d l i s t . T h e d e f a u l t i s t o i n c l u d e a l l h e a d i n g l e v e l s . * T h e s e c o n d p a r a m e t e r c a n b e u s e d t o s p e c i f y a c u s t o m t i t l e ( t h e d e f a u l t i s n o t i t l e ) . * T h e t h i r d p a r a m e t e r s e l e c t s t h e s t y l e o f t h e o u t l i n e . T h i s c a n b e e i t h e r ` i n l i n e ` o r ` p u l l o u t ` ( t h e l a t t e r b e i n g t h e d e f a u l t ) . T h e ` i n l i n e ` s t y l e r e n d e r s t h e o u t l i n e a s n o r m a l p a r t o f t h e c o n t e n t , w h i l e ` p u l l o u t ` c a u s e s t h e o u t l i n e t o b e r e n d e r e d i n a b o x t h a t i s b y d e f a u l t f l o a t e d t o t h e r i g h t s i d e o f t h e o t h e r c o n t e n t . * T h e f o u r t h p a r a m e t e r s p e c i f i e s w h e t h e r t h e o u t l i n e i s n u m b e r e d o r n o t . I t c a n b e e i t h e r ` n u m b e r e d ` o r ` u n n u m b e r e d ` ( t h e f o r m e r b e i n g t h e d e f a u l t ) . T h i s p a r a m e t e r o n l y h a s a n e f f e c t i n ` i n l i n e ` s t y l e .

[[ProjectStats]]

Wiki macro listing some generic Trac statistics.

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

• wiki -- statistics for TracWiki, values:
  • count -- show wiki page count
• prefix -- use with wiki key: only names that start with that prefix are included

'count' is also recognized without prepended key name.

[[RecentChanges]]

L i s t a l l p a g e s t h a t h a v e r e c e n t l y b e e n m o d i f i e d , o r d e r e d b y t h e t i m e t h e y w e r e l a s t m o d i f i e d . T h i s m a c r o a c c e p t s t w o o r d e r e d a r g u m e n t s a n d a n a m e d a r g u m e n t . T h e n a m e d a r g u m e n t c a n b e p l a c e d i n a n y p o s i t i o n w i t h i n t h e a r g u m e n t l i s t . T h e f i r s t p a r a m e t e r i s a p r e f i x s t r i n g : i f p r o v i d e d , o n l y p a g e s w i t h n a m e s t h a t s t a r t w i t h t h e p r e f i x a r e i n c l u d e d i n t h e r e s u l t i n g l i s t . I f t h i s p a r a m e t e r i s o m i t t e d , a l l p a g e s a r e i n c l u d e d i n t h e l i s t . T h e s e c o n d p a r a m e t e r i s t h e m a x i m u m n u m b e r o f p a g e s t o i n c l u d e i n t h e l i s t . T h e ` g r o u p ` p a r a m e t e r d e t e r m i n e s h o w t h e l i s t i s p r e s e n t e d : ` g r o u p = d a t e ` : : T h e p a g e s a r e p r e s e n t e d i n b u l l e t e d l i s t s t h a t a r e g r o u p e d b y d a t e ( d e f a u l t ) . ` g r o u p = n o n e ` : : T h e p a g e s a r e p r e s e n t e d i n a s i n g l e b u l l e t e d l i s t . T i p : i f y o u o n l y w a n t t o s p e c i f y a m a x i m u m n u m b e r o f e n t r i e s a n d d o n ' t w a n t t o f i l t e r b y p r e f i x , s p e c i f y a n e m p t y f i r s t p a r a m e t e r , e . g . ` [ [ R e c e n t C h a n g e s ( , 1 0 , g r o u p = n o n e ) ] ] ` .

[[RepositoryIndex]]

D i s p l a y t h e l i s t o f a v a i l a b l e r e p o s i t o r i e s . C a n b e g i v e n t h e f o l l o w i n g n a m e d a r g u m e n t s : ' ' f o r m a t ' ' : : S e l e c t t h e r e n d e r i n g f o r m a t : - ' ' c o m p a c t ' ' p r o d u c e s a c o m m a - s e p a r a t e d l i s t o f r e p o s i t o r y p r e f i x n a m e s ( d e f a u l t ) - ' ' l i s t ' ' p r o d u c e s a d e s c r i p t i o n l i s t o f r e p o s i t o r y p r e f i x n a m e s - ' ' t a b l e ' ' p r o d u c e s a t a b l e v i e w , s i m i l a r t o t h e o n e v i s i b l e i n t h e ' ' B r o w s e V i e w ' ' p a g e ' ' g l o b ' ' : : D o a g l o b - s t y l e f i l t e r i n g o n t h e r e p o s i t o r y n a m e s ( d e f a u l t s t o ' * ' ) ' ' o r d e r ' ' : : O r d e r r e p o s i t o r i e s b y t h e g i v e n c o l u m n ( o n e o f " n a m e " , " d a t e " o r " a u t h o r " ) ' ' d e s c ' ' : : W h e n s e t t o 1 , o r d e r b y d e s c e n d i n g o r d e r ( ' ' s i n c e 0 . 1 2 ' ' )

[[TitleIndex]]

I n s e r t a n a l p h a b e t i c l i s t o f a l l w i k i p a g e s i n t o t h e o u t p u t . A c c e p t s a p r e f i x s t r i n g a s p a r a m e t e r : i f p r o v i d e d , o n l y p a g e s w i t h n a m e s t h a t s t a r t w i t h t h e p r e f i x a r e i n c l u d e d i n t h e r e s u l t i n g l i s t . I f t h i s p a r a m e t e r i s o m i t t e d , a l l p a g e s a r e l i s t e d . I f t h e p r e f i x i s s p e c i f i e d , a s e c o n d a r g u m e n t o f v a l u e ` h i d e p r e f i x ` c a n b e g i v e n a s w e l l , i n o r d e r t o r e m o v e t h a t p r e f i x f r o m t h e o u t p u t . A l t e r n a t e ` f o r m a t ` a n d ` d e p t h ` n a m e d p a r a m e t e r s c a n b e s p e c i f i e d : - ` f o r m a t = c o m p a c t ` : T h e p a g e s a r e d i s p l a y e d a s c o m m a - s e p a r a t e d l i n k s . - ` f o r m a t = g r o u p ` : T h e l i s t o f p a g e s w i l l b e s t r u c t u r e d i n g r o u p s a c c o r d i n g t o c o m m o n p r e f i x . T h i s f o r m a t a l s o s u p p o r t s a ` m i n = n ` a r g u m e n t , w h e r e ` n ` i s t h e m i n i m a l n u m b e r o f p a g e s f o r a g r o u p . - ` f o r m a t = h i e r a r c h y ` : T h e l i s t o f p a g e s w i l l b e s t r u c t u r e d a c c o r d i n g t o t h e p a g e n a m e p a t h h i e r a r c h y . T h i s f o r m a t a l s o s u p p o r t s a ` m i n = n ` a r g u m e n t , w h e r e h i g h e r ` n ` f l a t t e n t h e d i s p l a y h i e r a r c h y - ` d e p t h = n ` : l i m i t t h e d e p t h o f t h e p a g e s t o l i s t . I f s e t t o 0 , o n l y t o p l e v e l p a g e s w i l l b e s h o w n , i f s e t t o 1 , o n l y i m m e d i a t e c h i l d r e n p a g e s w i l l b e s h o w n , e t c . I f n o t s e t , o r s e t t o - 1 , a l l p a g e s i n t h e h i e r a r c h y w i l l b e s h o w n . - ` i n c l u d e = p a g e 1 : p a g e * 2 ` : i n c l u d e o n l y p a g e s t h a t m a t c h a n i t e m i n t h e c o l o n - s e p a r a t e d l i s t o f p a g e s . I f t h e l i s t i s e m p t y , o r i f n o ` i n c l u d e ` a r g u m e n t i s g i v e n , i n c l u d e a l l p a g e s . - ` e x c l u d e = p a g e 1 : p a g e * 2 ` : e x c l u d e p a g e s t h a t m a t c h a n i t e m i n t h e c o l o n - s e p a r a t e d l i s t o f p a g e s . T h e ` i n c l u d e ` a n d ` e x c l u d e ` l i s t s a c c e p t s h e l l - s t y l e p a t t e r n s .

[[TracAdminHelp]]

D i s p l a y h e l p f o r t r a c - a d m i n c o m m a n d s . E x a m p l e s : { { { [ [ T r a c A d m i n H e l p ] ] # a l l c o m m a n d s [ [ T r a c A d m i n H e l p ( w i k i ) ] ] # a l l w i k i c o m m a n d s [ [ T r a c A d m i n H e l p ( w i k i e x p o r t ) ] ] # t h e " w i k i e x p o r t " c o m m a n d [ [ T r a c A d m i n H e l p ( u p g r a d e ) ] ] # t h e u p g r a d e c o m m a n d } } }

[[TracGuideToc]]

D i s p l a y a t a b l e o f c o n t e n t f o r t h e T r a c g u i d e . T h i s m a c r o s h o w s a q u i c k a n d d i r t y w a y t o m a k e a t a b l e - o f - c o n t e n t s f o r t h e H e l p / G u i d e . T h e t a b l e o f c o n t e n t s w i l l c o n t a i n t h e T r a c * a n d W i k i F o r m a t t i n g p a g e s , a n d c a n ' t b e c u s t o m i z e d . S e a r c h f o r T o c M a c r o f o r a a m o r e c u s t o m i z a b l e t a b l e o f c o n t e n t s .

[[TracIni]]

P r o d u c e d o c u m e n t a t i o n f o r t h e T r a c c o n f i g u r a t i o n f i l e . T y p i c a l l y , t h i s w i l l b e u s e d i n t h e T r a c I n i p a g e . O p t i o n a l a r g u m e n t s a r e a c o n f i g u r a t i o n s e c t i o n f i l t e r , a n d a c o n f i g u r a t i o n o p t i o n n a m e f i l t e r : o n l y t h e c o n f i g u r a t i o n o p t i o n s w h o s e s e c t i o n a n d n a m e s t a r t w i t h t h e f i l t e r s a r e o u t p u t .

[[UserQuery]]

Wiki macro listing users that match certain criteria.

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

• perm -- show only that users, a permission action given by value has been granted to
• locked -- retrieve users, who's account has/has not been locked depending on boolean value
• format -- output style: 'count', 'list' or comma-separated values (default)
• nomatch -- replacement wiki markup that is displayed, if there's no match and output style isn't 'count' either

'count' is also recognized without prepended key name. Other non-keyed parameters are:

• locked -- alias for 'locked=True'
• visit -- show a list of accounts with last-login information, only available in table format
• name -- forces replacement of maching username with their corresponding full names, if available; adds a full names column if combined with 'visit'
• email -- append email address to usernames, if available

Requires USER_VIEW permission for output in any format other then 'count'. A misc placeholder with this statement is presented to unprivileged users.

Macros from around the world

The ​Trac Hacks site provides a wide collection of macros and other Trac 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 ​Python programming language and are developed as part of TracPlugins.

For more information about developing macros, see the ​development resources on the main project site.

Here are 2 simple examples showing how to create a Macro with Trac 0.11.

Also, have a look at ​Timestamp.py for an example that shows the difference between old style and new style macros and at the ​macros/README which provides a little more insight about the transition.

Macro without arguments

To test the following code, you should saved it in a timestamp_sample.py file located in the TracEnvironment's plugins/ directory.

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, text):
        t = datetime.now(utc)
        return tag.b(format_datetime(t, '%c'))

Macro with arguments

To test the following code, you should saved it in a helloworld_sample.py file located in the TracEnvironment's plugins/ directory.

from genshi.core import Markup

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 WikiMacros page).
    """

    revision = "$Rev$"
    url = "$URL$"

    def expand_macro(self, formatter, name, text, 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'`),
        `text` 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 `text` is `None`.
        `args` are the arguments passed when HelloWorld is called using a
        `#!HelloWorld` code block.
        """
        return 'Hello World, text = %s, args = %s' % \
            (Markup.escape(text), Markup.escape(repr(args)))

Note that expand_macro optionally takes a 4^th parameter args. When the macro is called as a WikiProcessor, it's also possible to pass key=value processor parameters. If given, those are stored in a dictionary and passed in this extra args parameter. On the contrary, when called as a macro, args is None. (since 0.12).

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 by yourself (using return Markup.escape(result)) or, if this is indeed HTML, wrap it in a Markup object (return Markup(result)) with Markup coming from Genshi, (from genshi.core import Markup).

You can also recursively use a wiki Formatter (from trac.wiki import Formatter) to process the text as wiki markup, for example by doing:

from genshi.core import Markup
from trac.wiki.macros import WikiMacroBase
from trac.wiki import Formatter
import StringIO

class HelloWorldMacro(WikiMacroBase):
        def expand_macro(self, formatter, name, text, args):
                text = "whatever '''wiki''' markup you want, even containing other macros"
                # Convert Wiki markup to HTML, new style
                out = StringIO.StringIO()
                Formatter(self.env, formatter.context).format(text, out)
                return Markup(out.getvalue())