haiku/docs/user/apidoc.dox

/*
 * Copyright 2007 Niels Sascha Reedijk. All rights reserved.
 * Distributed under the terms of the MIT License.
 *
 * Authors:
 *		Niels Sascha Reedijk, niels.reedijk@gmail.com
 * Proofreaders:
 *		Alan Smale, ajsmale@gmail.com
 */


/*!
	\page apidoc Documenting the API
	
	This article explains how to document the API. Its intended audience are the
	Haiku developers who want to document their own classes, and also the
	members of the API Documentation team who want to brush up the
	documentation. The guidelines are synchronous with the Haiku Coding
	Guidelines, which means that the formal requirements are the same where
	applicable. If you find an inconsistency, it's usually a good idea to
	report this on the documentation team's mailing list.
	
	This document is divided into three sections. \ref formalrequirements
	describes the demands that are made from the markup and spacing of the
	files. \ref commands describes the subset of Doxygen commands the Haiku API
	documentation uses, and which commands are used in which situation. \ref
	style describes the required style and structure of the documentation. If
	you are a developer and you want to prepare the first version of the
	documentation for the API documentation team to go over, have a good look at
	the formal requirements and the Doxygen commands. In addition, have a quick
	glance at how to write member and class documentation, since you'll need to
	know which information is mandatory for the documentation. Aspiring members
	or members of the API documentation team should read the third section
	carefully, and should also check out some of the finished documentation to
	get a good grip on the actual tone, style and contents of the documentation.

	\section formalrequirements Formal Requirements

	This section describes formal requirements, such as location and naming of
	the files, the header blocks of files, what blocks of documentation look
	like and how to put delimiters to separate different 'blocks' in your source
	file.

	\subsection formalrequirements_location Location of the Documentation Source

	Doxygen, the tool that we use to generate the marked up documentation, has
	an ingenious parser that is able to scan through both header and source
	files making it possible to document the API directly in the headers or the
	source. However, the Haiku project have decided not to put the documentation
	in either location, and opt for the third option Doxygen provides: to put
	the documentation into separate files.

	\note The reasons to not put the documentation in the header files are
		twofold. First of all, it would add unnecessary cruft to the headers
		that the compiler will needlessly have to parse. File access and speed
		isn't BeOS and Haiku's best quality. The second reason is that the
		system headers are included throughout the tree. It's a waste of
		electricity to have everybody recompile the entire tree if someone fixes
		a typo in the documentation. Likewise, the reason to not put the
		documentation in the source code is that it unnecessarily clutters up
		that file. By not using direct documentation we lose some advantages,
		like the fact that developers might be inclined to update the
		documentation quicker if they change a method, but as you will see we'll
		have some methods in place to prevent that to a certain extent.
		There are a few aspects to the naming and locations of files:
		-# Most important, documentation files \b mirror header files. This
			not only means that they get the same name, but also that the order
			of the methods, variables, functions, etc. will have to be the same.
		-# The root directory of the public API headers is at \c
			/trunk/headers/os. In a similar vein, the root of the documentation
			files is at \c /trunk/src/documentation/haiku_book. The subdirectory
			structure, or the division of kits, will also be replicated.
		-# The name of the files is the same as the base of the header files,
			with the \c dox extension. So \c Something.h becomes \c
			Something.dox. Note the case!

	\subsection formalrequirements_headerblock The Header Block

	Every documentation file will begin with the header block. It's basically a
	copyright block, with a reference to the author(s) and against which
	revision the documentation was written.

	\verbatim
/*
* Copyright 2007 Niels Sascha Reedijk. All rights reserved.
* Distributed under the terms of the MIT License.
*
* Authors:
*		Niels Sascha Reedijk, niels.reedijk@gmail.com
* Proofreaders:
*		Alan Smale, ajsmale@gmail.com
* Corresponds to:
*		/trunk/headers/os/support/String.h  rev 19731
*		/trunk/src/kits/support/String.cpp  rev 19731
*/
	\endverbatim

	The example above has a few elements that you should take note of:
	-# The header is put in a standard C comment, which is enclosed between \c
		/* and \c *\/.
	-# Every line starts with a whitespace and an asterix, followed by another
		space. If the text is part of a category, such as <tt>Authors</tt>, put
		three spaces after the delimiter. 
	-# The first line is empty, then we get to the copyright notice. You may
		either retain the copyright yourself, or you can attribute to to Haiku
		Inc. It's your choice. The next line is the \e MIT licence notice,
		followed by an empty line.
	-# Then there is a label <tt>Authors:</tt>, which is followed by
		lines with names and email addresses. The latter one is optional, but
		recommended. Each author is preceeded by two tabs after the asterix.
	-# In the same vein there is the label <tt>Proofreaders:</tt> in case the
		file has been proofread.
	-# The final part is underneath the label <tt>Corresponds to:</tt>.
		Underneath there is a list of files and their svn revisions that the
		current documentation is known to correspond with.
	-# The header block ends with the \c *\/, where the asterix is aligned with
		the ones above it.

	\subsection formalrequirements_blocks Blocks
	
	Blocks are the basic units of documentation for Doxygen. At first it will
	feel like overkill to use blocks, but realize that Doxygen was initially
	designed to operate on header and source files, and then the blocks of
	documentation would be before the definition or declaration of the methods,
	functions, etcetera. Doxygen is used to operating on blocks, and that's why
	we need to reproduce them in our \c dox files.

	Blocks should adhere to the following standards:
	-# All blocks open with \c /*! and close with \c * /
	-# The documentation is placed in between these markers.
	-# All the contents in between the markers is indented by tabs. The tab
		length should be four.
	-# Between blocks, there should be two empty lines.
	-# The maximum width of the contents between blocks is 80 columns. <em>Try
		not to cross this limit</em>, because it will severely limit
		readability.
	
	Example:
	\verbatim
/*!
	\fn bool BList::AddItem(void *item)
	\brief Append an item to the list.
	
	\param item The item to add.
	\retval true The item was appended.
	\retval false Item was not appended, since resizing the list failed.
	\sa AddItem(void *item, int32 index)
*/
	\endverbatim
	
	\note Doxygen also allows the use of single line comments, starting with 
		\c //!, however, we won't use these \b except for group markers, which
		you can read more about in the next section.

	\subsection formalrequirements_delimiters Delimiters

	Many of the header files in the Haiku API just document one class or one
	group of functions. However, there be a time when you come across a more
	complex header and for the sake of clarity in your \c dox file you want to
	mark the sections. Use the standard delimiter marker for this, which
	consists of five slashes, a space, the title of the section, a space and
	another five slashes. Like this: <tt>///// Global Functions /////</tt>.

	\note This is only for the source files and for you as documenter. It will
		not show up in the actual generated documentation!

	\section commands Doxygen Commands

	This section describes all the Doxygen commands that will be used in the
	Haiku API documentation. As a rule, Doxygen commands start with a backslash
	(\\) and are followed by whitespace (such as a space or a newline), with the
	exception of group markers; this is discussed in more detail later on. The
	commands can be divided into several categories, which are described in the
	following subsections.

	\note This section does not discuss which commands you should actually use
		in documentation. See the next section on \ref style for that. This
		section merely explains the different groupings and syntaxes of
		commands.

	Most commands accept an argument. Arguments can be one of these three types:
	- \<single_word\> - The argument is a single word.
	- (until the end of the line) - The argument runs until the end of the line.
	- {paragraph} - The argument runs for an entire paragraph. A paragraph is
		ended by an empty line, or if another command that defines a \ref
		commands_sections sections is found. Note that if you use commands that
		work on a paragraph and you split it over multiple lines (because of the
		maximum line width of 80 characters or because it looks better), you
		will have to indent subsequent lines that belong to the paragraph with
		two more spaces, making the total of four. This is to visually
		distinguish paragraphs for other documenters.

	\subsection commands_definitions Block Definitions

	Because our API documentation is not done in the source, nor in the headers,
	Doxygen needs to be helped with figuring out what the documentation in the
	different blocks actually are about. That's why the first line in a
	documentation block would be one of the following commands:

	- \c \\class \<name\> \n
		Tells Doxygen that the following section is going to be on the class as
		specified by \a name.
	- \c \\fn (function declaration) \n
		This block is going to be about the function that corresponds to the
		given declaration. Please note that the declaration is what you find in
		the source file, so if class members are declared, the classname and the
		scope operator, \c ::, are to be added as well. Modifiers such as \c
		const should be included.
	- \c \\var (variable declaration) \n
		This block is going to be about the variable indicated by the
		declaration. This means basically that data members of a class should
		have the classname and the scope operator as well.
	- \c \\typedef (typedef declaration) \n
		This block is going to be about the typedef indicated by the
		declaration. Copy the declaration exactly, including the leading \c
		typedef keyword.
	- \c \\struct \<name\> \n
		Tells Doxygen the section is going to be on the \c struct indicated by
		\a name. 
	- \c \\def \<name\> \n
		This block is going to be about the \c \#define with the identifier \a
		name. 
	- \c \\page \n
		This block represents a page. See the section on \ref commands_pages for
		detailed information on pages.

	\subsection commands_sections Sections in Member Documentation

	If you have a look at the output that Doxygen generates, you can see that
	there are recurring sections in the documentation. Documentation that
	belongs to a certain section should be placed after a command that marks the
	start of that section. All the commands take a paragraph as answer. A
	paragraph ends with a whitespace, or with a command that marks a new
	section. Note that this list only shows the syntax of the commands. For the
	semantics, have a look at the next section on style. In member documentation
	you can use the following:

	- \c \\brief {brief description} \n
		This is the only \b mandatory section. Every member should have at least
		a brief description. 
	- \c \\param \<parameter-name\> {parameter description} \n
		This section describes a parameter with the name \a parameter-name. The
		parameter name must match the function declaration, since Doxygen will
		check if all the documented parameters exist.
	- \c \\return {description of the return value} \n
		This section describes the return value. This is a totally free form
		paragraph, whereas \c \\retval has a more structured form.
	- \c \\retval \<value\> {description} \n
		This section describes the return value indicated by \a value. 
	- \c \\see {references} \n
		This section contains references to other parts of the documentation.

	There are also a number of things that can be used in pages and member
	documentation. See the style section to find out the appropriate situations
	in which to use them.

	- \c \\note {text}
	- \c \\attention {text}
	- \c \\warning {text}
	- \c \\remarks {text}

	\subsection commands_markup Markup

	Sometimes you might require certain text to have a special markup, to make
	words stand out, but also if you want to have example code within the
	documentation you'll need a special markup. Doxygen defines three types of
	commands. There are commands that work on single words, commands that work
	on longer phrases and commands that define blocks. Basically, the single
	letter commands are commands that work on a the next word. If you need to
	mark multiple words or sentences, use the HTML-style commands. Finally, for
	blocks of code or blocks of text that need to be in "typewriter" font, use
	the block commands. Have a look at the following listing:

	- \c \\a \n
		Use to refer to parameters or arguments in a running text, for example
		when referring to parameters in method descriptions.
	- <b>Bold text</b>
		- For single words, use \c \\b.
		- For multiple words, enclose between the \c \<b\> and \c \<\\b\> tags.
	- <tt>Typewriter font</tt> \n
		This can be used to refer to constants, or anything that needs to be in
		a monospace, or typewriter, font. There are a few options
		- \c \\c for single words.
		- \c \<tt\> and \c \<\\tt\> for multiple words or phrases
		- The commands \c \\verbatim and \c \\endverbatim. Everything between
			these two commands will be put in a distinct block that stands out
			from the rest of the text.
		- The commands \c \\code and \c \\endcode do the same, but Doxygen will
			parse the contents and try to mark up the code to make it look a
			little bit nicer.
	- <em>Emphasis</em>
		- \c \\e for single words.
		- \c \<em\> and \c \<\\em\> for phrases.

	\subsection commands_pages Page Commands

	Pages are a very special element of the documentation. They are not 
	associated with any kind of module, such as files or classes, and therefore,
	since they're not members, some of the structuring commands won't work.
	Important to know is that a page is the complete length of the block, so
	dividing it up in subsections by starting new blocks will not work. Instead,
	Doxygen provides some commands to structure text on a page.

	First of all, you define a new page by using the \c \\page command. This
	command takes two arguments: a \c \<name\> and <tt>(a title)</tt>. The name
	is the internal identifier that can be used in linking between pages (see
	\ref commands_miscellaneous for \c \\ref). After you've defined the block
	to be a page, you can start writing the contents. 

	For more complicated pages,  you might want to divide the page up in
	sections. Use the \c \\section command to define a new section. It takes the
	same arguments as \c \\page, namely the \c \<name\> and the
	<tt>(title)</tt>. If you need a deeper hierarchy you may use \c \\subsection
	and \c \\subsubsection, again, both with the same syntax. If you need to
	distinguish between sections in subsubsections, you are able to use 
	\c \\paragraph, which takes the same arguments.

	\note Before and after each of the commands above, you need to have an empty
		line so as to provide readability. It is not necessary to indent
		sections and subsections more than the normal two spaces, as long as you
		keep the section markers clear.

	\warning If you are entering the realm of subsections and sub-subsections,
		think about the nature of your page. Either it needs to be split up into
		multiple pages, or what you're writing is too complex and would be
		better off as a big tutorial on the Haiku website.

	If you are creating multiple pages that are related, you will be able to
	structure them in a tree by using the \c \\subpage command. This will rank
	the different pages in a tree structure. It will put a link in the place of
	the command, so you should place it at the top of the parent place and use
	it as an index.

	\subsection commands_grouping  Member Grouping Commands

	Doxygen makes it possible to group certain members together. It is used
	in the BString class for example, where the members are grouped by what kind
	of operation they perform, such as appending, finding, etc. Defining groups
	is currently not as powerful as it could be, but if you use it inside
	classes, you will be fine if you follow the instructions presented in
	this section.

	\note If you are looking on how to add classes to kits, see
		\ref commands_miscellaneous and have a look at the \c \\ingroup command.

	Groups of members are preceded by a block that describes what the group is
	about. You are required to give each group of members at least a name. Have
	a look at the example: 

\verbatim
/*!
	\\name Appending Methods
	
	These methods append things to the object.
*/


//! \@{

... names of the methods ...

//! \@}
\endverbatim

	The block preceding the block opening marker, <tt>//! \@{</tt>, contains a
	\c \\name command and a paragraph that gives a description. The header
	block can be as long or short as you want, but please don't make it too
	long. See the \ref style section on how to effectively write group headers.
	The members that you want to belong to the group are between the group
	opening and closing markers.

	\note Group headers don't have a \c \\brief description.

	\subsection commands_miscellaneous Miscellaneous Commands

	There are some commands that don't fit into the categories above, but that
	you will end up using every now and then. This section will describe those
	commands.

	The first one is \c \\n. This commands sort of belongs to the category of
	markup commands. It basically forces a newline. Because Doxygen parses
	paragraphs as a single contiguous entity, it's not possible to mark up the
	text using carriage returns in the documentation. \c \\n forces a newline in
	the output. So in HTML it will be translated into a \c \<br\\\>.

	Sometimes there are some parts of the API that you don't want to be visible.
	Since Doxygen extracts all the public and protected members from a class,
	and virtually every member from a file, you might want to force it to hide
	certain things. If so, use the \c \\internal command. If you place this just
	after the block marker, the command will be hidden from documentation. Any
	further documentation or remarks you put inside the block will not be
	visible in the final documentation. 

	Images can be a valuable addition to documentation. To include ones you
	made, use the \c \\image command. It has the following prototype:
	<tt>\\image \<format\> \<file\></tt>. The format is currently fixed at
	\c html. The file refers to the filename relative to the location of the
	documentation file. Any images you want to add should be in the same
	location as the dox file, so only the file name will suffice.

	Modules are defined in the main book, and you can add classes to them by
	using the \c \\ingroup command. This commands adds the class to the module
	and groups it on a separate page. At this moment, the group handling has yet
	to be finalised. For now, add the classes to the kit they belong in. In the
	future this might change.

	Finally, it is a good idea to link between parts of the documentation. There
	are two commands for that. The first one is \c \\ref, which enable you to
	refer to pages, sections, etc. that you created yourself. The second one is
	\c \\link which refers to members. The first one is takes one word as an
	argument, the name of the section, and it inserts a link with the name of
	the title. \c \\link is more complex. It should always be accompanied by \c
	\\endlink. The first word between the two commands is the object that is
	referred to, and the rest is the link text. 

	\section style Writing Guidelines

	This final section will present guidelines for the actual writing of the
	documentation. Both the structure of the documentation, which sections to
	use when, and the style of the writing will be discussed. Before diverging
	into the requirements for file and class descriptions, member descriptions
	and pages, there are some general remarks that apply to all types of
	documentation.

	First of all, everything you write should be in <em>proper English 
	sentences</em>. Spelling, grammar, punctuation, make sure you adhere to the
	standards. It also means the following:
	- It means that every sentence should at least have a
		subject and a verb (unless it's an imperative statement).
	- Also use the proper terminology. Remember, you are dealing with C++
		here, which means you should use the right names. So use \b method
		instead of function, and data member instead of variable (where
		appropriate). 
	- Avoid informalism. Avoid constructs like 'if you want to
		disconnect the object', but rather use 'to disconnect the object'. Avoid
		familiarisms, or jokes.
	
	\remarks It isn't the goal to create dry, legal-style documentation. Just
		try to find a balance. Read through documentation that's already been
		approved to get a hint of what you should be aiming for.
	\remarks If you are having a problem with phrasing certain things, put it
		down in such a way that it says everything it needs to. A proofreader
		might then be able to rephrase it to a better style.

	Throughout the documentation you might want to provide hints, warnings or
	remarks that might interrupt the flow of the text, or that need to visually
	stand out from the rest. Doxygen provides commands for paragraphs that
	display remarks, warnings, notes and points of attention. You can use these
	commands in case you meet one or more of the following requirements:
	- The point is for a specific audience, such as beginners in the Haiku API.
		Notes on what to read first, or mistakes that may be made by beginners
		will not be for the entire audience, and such should be separated. These
		kinds of notes should be at the end of blocks.
	- The point needs to visually stand out. This is especially the case with
		remarks, but could also apply for other types.
	- The point is not completely relevant to the text and therefore should be
		separated so that it doesn't interrupt the main flow.

	This listing shows which one to use for which situation:
	- \c \\attention
		- Used when the developer is bound to make a mistake, when the API is
			ambiguous. The difference between this and a warning is that
			warnings warn about things that are the developers fault, and
			attention blocks warn about things that might go wrong
			because of the way the API is	structured.
		- Used to warn for abuse of the API that might be caused by the way the
			internals of the system are structured.
	- \c \\warning
		- Used to warn developers about using the API in a certain way. Warnings
			apply especially to new developers that aren't completely familiar
			with the API and that might want to abuse it. For example, the
			thread safety of BString requires a warning.
	- \c \\note
		- Used to place references to other documentation that might not be
			directly related to the text. For example, BLooper will have a
			direct reference to BHandler in the class description, but
			BMessenger will be mentioned in a note because it does not directly
			influence the use of the class.
		- Can also be used for useful hints or notes that somehow need to stand
			out from the rest of the text.
	- \c \\remarks
		- Remarks are small notes that would interrupt the flow of the text. For
			example, if you in a text ignore a certain condition that is so
			extremely rare and uncommon, you can put a remark at the end of the
			text to tell that you have been lying.
		- Remarks interact with the text whereas notes add something unmentioned
			to it.

	\subsection style_files File Descriptions

	The design of Doxygen makes it very file oriented, and this might come off
	as inconvenient. At the moment, how to actually group the documentation is
	still under debate, but it does not change the requirement that a header
	needs to be documented before the members of that header can be documented.
	As such, the first documentation block in your \c dox file will be the block
	that describes the header. Examples:

\verbatim
/*!
	\file String.h
	\brief Defines the BString class and global operators and functions for 
		handling strings.
*/


/*!
	\file SupportDefs.h
	\brief Defines basic types and definitions for the Haiku API.
*/ 
\endverbatim

	The first statement defines what the block is about, namely the header file.
	The second element is the \c \\brief remark on what it contains. The first
	file defines the BString class and some global operators. You can see that
	reflected in the description. SupportDefs.h does not define classes, but
	rather a range of different functions and defines, so the text refers to
	that.

	\remarks \\brief documentation for files is about what it \e implements, as
		header files are passive (whereas members and functions are active).
		Thus, use the third person form of the verb.

	\subsection style_classes Class Descriptions

	Classes are the basic building blocks in the Haiku API and as such have
	extensive documentation. This section will go over the actual class
	description. This section will present a list of items you should think
	about when writing the class description. This doesn't mean you'll have
	to include every item, it merely serves as a guiding principle that helps
	organise your thoughts. Have a look at the list:

	-# The \c \\brief description is \b obligatory. This description describes
		what it is. For example, BDataIO: "Abstract interface for objects that
		provide read and write access to data." Note that this description is
		not a full sentence, but it does end with a period.
	-# One or more paragraphs that give a broad overview of what the class can
		do. Describe things like what it works on, when you want to use it, what
		advantage it might give over other directly related alternatives. Also
		describe if a class is made to be derived from, and if so, how. Make
		sure that a developer in the first few paragraphs can judge if what he
		wants to do can be done with this class. 
	-# One or more paragraphs that show how this class ties in with the rest
		of the kit or the API. What objects does it work with, how it interacts
		with the servers, etcetera. 
	-# One or more paragraphs that give a concrete example or use case. Keep it
		tidy and self contained. If you use code examples, make sure your
		examples adhere to Haiku's coding guidelines. Remember, an example can
		illustrate better than a few paragraphs of text.
	-# End with a list of references to other classes, functions, pages, etc.
		that might be of interest to the reader.

	When documenting classes, don't be to exhaustive. Avoid becoming a tutorial
	or a complete guide. This documentation is for reference only. If you want
	to enlighten the reader on bigger subjects, consider writing a separate
	documentation page that connects the different points you want to make.

	Also, you don't have to put in any groupings of members in class
	descriptions. If you want to do that, physically divide the members up in
	groups. Look at the \ref commands_grouping for the actual commands, and at
	\ref style_groups for help on writing group headers.

	\subsection style_members Members and Functions

	Members and functions share the same basic Doxygen syntax, and they can be
	documented in a similar way. That's why this section deals with them
	together. Documenting members is probably the main thing you'll do when
	writing the actual documentation. There are some guidelines as to how, but
	the actual implementation probably differs per class. Keep the following
	points in mind:

	-# To repeat a very important fact, the first line is a \c \\fn line. This
		line needs to match the declaration, which is in the source file. This
		means that for members, also the class name and the scope indicator (::)
		should be present. Also note that this line doesn't have to adhere to
		the 80 column width limit.
	-# The first command is always the \c \\brief command. Give a short and
		clear description. The description starts with a capital letter and ends
		with a dot. Don't write the description saying what the method does,
		like "Starts the timer", but rather as what it will do: "Start the
		timer." -# If the brief description doesn't cover all of what the method
		or function does, then you can add a few paragraphs that explain it in
		more depth. Don't be too verbose, and use an example to illustrate
		points. Point out any potential misunderstandings or problems you expect
		developers to have, but don't repeat the class documentation too much.
	-# You are obliged to then document all the parameters. Use the \c \\param
		command for that. For the description, use a short phrase such as "The 
		offset (zero based) where to begin the move." Note the capital and the
		dot.
	-# If the function is non-void, then you'll have to specify what it will
		return. In case of fixed values, have a look at \c \\retval. You'll use
		this one when the return type is a bool or a status_t. In case of
		something else, use \c \\return. You can also combine these two. For
		example, a method that returns a length (positive) or an error code
		(negative).
	-# Use \c \\see if you have any references to other methods, classes or
		global functions. At least document all the overloaded methods. Also add
		methods that do the opposite of this method, or methods that are
		intimately related.

	In case of overloaded members, you'll need to make a decision. If you need
	to copy too much information, you might resort to putting it in one
	paragraph with the text "This is an overloaded member function, and differs
	from \<name\> only by the type of parameter it takes." That will keep the
	copying down and will point developers right to the place where they can get
	more documentation.

	Again, like class descriptions, you'll have to find a good middle-ground
	between too much information, and too little. Again, write for the broadest
	audience possible, and resort to notes and warnings for specialised 
	audiences.

	\subsection style_variables Enumerations, Variables and Defines

	This section helps you document (member) variables and defines that define
	constants, as well as enumerations and their values. If you need to document
	a \c \#define macro that takes arguments, have a look at \ref style_members

	The \c \\brief description of all these types follow a similar structure. 
	They are a short phrase that mention what the variable contains. Example:

\verbatim
	/*!
	\var char* BString::fPrivateData
	\brief BString's storage for data.
	
	This member is deprecated and might even become \c private in future
	releases.
	
	If you are planning to derive from this object and you want to manipulate
	the raw string data, please have a look at LockBuffer() and UnlockBuffer().
*/
\endverbatim

	The variables you are going to encounter are either \c public or 
	\c protected member variables, or global variables that have a certain
	significance. In the case of member variables, you'll need to document what
	they mean and how the developer should manipulate them. If the class is one 
	that is meant to be derived from, make sure that in the description of the
	variable you mention how it interacts with the others, and how the developer
	should make sure that the internal coherence of the data and code members of
	the inherited class is maintained. 

	Global variables will mostly be constants. If so, document what they stand
	for and what they might be used for, as well as which classes and functions
	depend on that constant. If the variable is meant to be changed by the
	developer, explain what values are valid and which functions and classes
	depend on this variable. 

	Defines are usually used as message constants. Give a short description of
	what the message constant stands for, and where it might be send from and
	where it might be received.

	Enumerations can either be anonymous or named. In case of the latter, you
	can give a description of the enumeration in a documentation block that
	starts with an \c \\enum command, followed by the name of the enumeration.
	If the enumeration is within the scope of a class, prepend the classname and
	the scope indicator. In case of an anonymous enum, you can only document the
	individual members (which you should do for the named enumerations as well),
	which can be done within code blocks that start with the \c \\var command.
	Doxygen will know that it's an enumeration value, don't worry about mixups.
	If the enumeration value is within a class, prepend the classname and scope
	indicator. Give a short description of the value, which methods react to
	it, where it might be used, etcetera. Don't go as far as to copy information
	too much. For example, if you use an enumeration in only one class and you
	document the possible values there, then don't do that again for the
	enumeration documentation: rather just refer to it. That sort of
	documentation belongs to the class description, not to the enumeration.

	\subsection style_groups Groups
	
	If you subdivide members of classes into groups, you have the ability to
	apply some general information that will be listed above the listing of the
	members in that group. See the section \ref commands_grouping on how to
	define groups. This section is on what to put in the header block.
	
	First of all, it's probably a good idea to give your group a name. This name
	will be printed as a title and will enhance the clarity of what the group
	contains. If you put the \c \\name command as the first command of a group,
	the rest of the words on that line will be used as the title. You should
	choose simple titles of no more than three words.
	
	It's possible to add one or two paragraphs of information. These paragraphs
	should contain some quick notes on which of the members in that group to use
	for what purpose. See it as a quick subdivision that a developer could use
	as a guide to see which method he actually wants to use. Don't go on
	describing the methods in detail though, that's what the member
	documentation is about. Have a look at the example:

\verbatim
/*!
	\name Comparison Methods
	
	There are two different comparison methods. First of all there is the whole
	range of operators that return a boolean value, secondly there are methods
	that return an integer value, both case sensitive and case insensitive.
	
	There are also global comparison operators and global compare functions.
	You might need these in case you have a sort routine that takes a generic
	comparison function, such as BList::SortItems().
	See the String.h documentation file to see the specifics, as they are
	basically the same as implemented in this class.
*/
\endverbatim

	Straight, to the point, gives no more information than necessary. Divides
	the members up into two groups and refers to other functions the developer
	might be looking for. The hard limit is two (short) paragraphs. Using more
	will not improve clarity.

*/