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/*
* Copyright 2007 Niels Sascha Reedijk. All rights reserved.
* Copyright 2008-2013, 2020 Haiku, Inc. All rights reserved.
* Distributed under the terms of the MIT License.
*
* Authors:
* Niels Sascha Reedijk, niels.reedijk@gmail.com
* John Scipione, jscipione@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, and developers will have a hard
time to find the info they are looking for. 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
headers/os. In a similar vein, the root of the documentation
files is at \c docs/user. 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 2007-2013 Haiku, Inc. 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:
* headers/os/support/String.h rev 19731
* 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
\verbatim
/*
\endverbatim
and
\verbatim
*/
\endverbatim
-# Every line starts with a whitespace and an asterisk 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 License 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 proceeded by two tabs after the asterisk.
-# 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
\verbatim
*/
\endverbatim
where the asterisk 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
\verbatim
/*!
\endverbatim
and close with
\verbatim
*/
\endverbatim
-# 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. <b>Try
not to cross this limit</b>, 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!
\subsection formalrequirements_internal Internal documentation
It is possible that there is documentation for parts of the API that are
not (yet) part of the public API. It could either be that the documentation
is part of the public header file (usually hidden behind a namespace like
\c BPrivate), or it is part of a private header file.
In case you are in the situation where you need to store private API docs,
you should put the entirety of the documentation in a conditional block,
with the \c INTERNAL identifier. You open the block with the command
<tt>//! \\cond INTERNAL</tt> and end the block with the command
<tt>//! \\endcond INTERNAL</tt>.
There are two different cases where you must or could use these blocks:
-# For non-public API of a <em>public header file</em>, you must always
add the classes and other elements to the documentation even if they
are placeholders, and put them in the conditional block.
-# For parts of the non-public API that is in a <em>private header
file</em>, you could put the documentation in a conditional block. If
you choose to do so, you must document all elements in that header
file.
\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 \link
commands_sections section \endlink 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 argument. A
paragraph ends with an empty line, 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 sub-sub-sections, 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.
*/
//! \@{
... 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 command 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 finalized. 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 takes one word as an
argument, the name of the section, and it inserts a link with the text 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 in-formalism. Avoid constructs like 'if you want to
disconnect the object', but rather use 'to disconnect the object'. Avoid
familiarizes, 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 too 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 sent 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.
*/
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