path: root/doc/docblocks.doc

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 * Copyright (C) 1997-2001 by Dimitri van Heesch.
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/*! \page docblocks Documenting the code

\subsection specialblock Special documentation blocks

The following types of special documentation blocks are supported by doxygen:
<ul>
<li>The Qt style, where special documentation blocks look like:
\verbatim
/*!
  ... text ...
*/
\endverbatim and the one line version:
\verbatim
//! ... one line of text ...
\endverbatim
<li>The JavaDoc style, where special documentation blocks look like:
\verbatim
/**
 * ... text ...
 */
\endverbatim and the one line version:
\verbatim
/// ... one line of text ...
\endverbatim
</ul>

Doxygen only allows one brief and one detailed description. If there is
one brief description before a declaration and one before a
definition, only the one before the \e declaration will be used. If
the same situation occurs for a detailed description,
the one before the \e definition is preferred and the one before the
declaration will be ignored.

Here is an example of a documented piece of C++ code using the Qt style:
\verbinclude qtstyle.cpp
 \htmlonly
 Click <a href="$(DOXYGEN_DOCDIR)/examples/qtstyle/html/class_test.html">here</a>
 for the corresponding HTML documentation that is generated by doxygen.
 \endhtmlonly

The one-line comments should contain a brief description, 
whereas the multi-line comment blocks contain a more detailed description.
Note that consecutive one-line comments are merged together in one brief 
description. The brief descriptions are included in the member overview of a 
class, namespace or file and are printed using a small italic font 
(this description can be hidden by setting 
\ref cfg_brief_member_desc "BRIEF_MEMBER_DESC" to \c NO in 
the config file). By default the brief descriptions become the first 
sentence of the detailed descriptions 
(but this can be changed by setting the \ref cfg_repeat_brief "REPEAT_BRIEF" 
tag to \c NO). Both the brief and the detailed descriptions are optional 
for the Qt style. 

By default a JavaDoc style documentation block behaves the same way as a
Qt style documentation block. This is not according the JavaDoc specification
however, where the first sentence of the documentation block is automatically
treated as a brief description. To enable this behaviour you should set
\ref cfg_javadoc_autobrief "JAVADOC_AUTOBRIEF" to YES in the configuration
file. If you enable this option and want to put a dot in the middle of a
sentence without ending it, you should put a backslash and a space after it.
Here is an example:
\verbatim
  /** Brief description (e.g.\ using only a few words). Details follow. */
\endverbatim

Here is the same piece of code as shown above, this time documented using the 
JavaDoc style and \ref cfg_javadoc_autobrief "JAVADOC_AUTOBRIEF" set to YES:
\verbinclude jdstyle.cpp
 \htmlonly
 Click <a href="$(DOXYGEN_DOCDIR)/examples/jdstyle/html/class_test.html">here</a>
 for the corresponding HTML documentation that is generated by doxygen.
 \endhtmlonly

Unlike most other documentation systems, doxygen also allows you to put
the documentation of members (including global functions) in front of 
the \e definition. This way the documentation can be placed in the source 
file instead of the header file. This keeps the header file compact, and allows the 
implementer of the members more direct access to the documentation.
As a compromise the brief description could be placed before the
declaration and the detailed description before the member definition.

\par Note:
Each entity can only have \e one brief and \e one detailed description. If you
specify more than one comment block of the same type, only one will be used,
and all others are ignored!

\subsection structuralcommands Structural commands

So far we have assumed that the documentation blocks are always located in 
front of the declaration or definition of a file, class or namespace or in
front of one of its members. 
Although this is often comfortable, it may sometimes be better to put the 
documentation somewhere else. For some types of documentation blocks (like file
documentation) this is even required. Doxygen allows you to put your
documentation blocks practically anywhere (the exception is inside the body 
of a function or inside a normal C style comment block), as long as you put a 
structural command inside the documentation block.

Structural commands (like all other commands) start with a backslash 
(<tt>\\</tt>), or an at-sign (<tt>\@</tt>) in JavaDoc style, 
followed by a command name and one or more parameters.
For instance, if you want to document the class \c Test in the example
above, you could have also put the following documentation block somewhere
in the input that is read by doxygen:
\verbatim
/*! \class Test
    \brief A test class.

    A more detailed class description.
*/
\endverbatim

Here the special command \c \class is used to indicate that the
comment block contains documentation for the class \c Test.
Other structural commands are:
<ul>
<li>\c \struct to document a C-struct.
<li>\c \union to document a union.
<li>\c \enum to document an enumeration type.
<li>\c \fn to document a function.
<li>\c \var to document a variable or typedef or enum value.
<li>\c \def to document a \#define.
<li>\c \file to document a file.
<li>\c \namespace to document a namespace.
</ul>
See section \ref commands for detailed information about these and other 
commands. Note that the documentation block belonging to a file 
should always contain a structural command.

To document a member of a C++ class, you must also document the class 
itself. The same holds for namespaces. To document a global C function, typedef, 
enum or preprocessor definition you must first document the file that 
contains it (usually this will be a header file, because that file contains 
the information that is exported to other source files).

Let's repeat that, because it is often overlooked:
to document global objects (functions, typedefs, enum, macros, etc), you
<em>must</em> document the file in which they are defined. In other words, 
there <em>must</em> at least be a \verbatim /*! \file */ \endverbatim
or a \verbatim /** @file */ \endverbatim line in this file.

Here is an example of a C header named \c structcmd.h that is documented 
using structural commands:
\verbinclude structcmd.h
 \htmlonly
 Click <a href="$(DOXYGEN_DOCDIR)/examples/structcmd/html/structcmd_8h.html">here</a>
 for the corresponding HTML documentation that is generated by doxygen.
 \endhtmlonly

\par Note:
  Because each comment block in the example above contains a structural command, all
  the comment blocks could be moved to another location or input file 
  (the source file for instance), without affecting the generated 
  documentation. The disadvantage of this approach is that prototypes are
  duplicated, so all changes have to be made twice!

\subsection memberdoc Documenting compound members.

If you want to document the members of a file, struct, union, class, or enum,
and you want to put the documentation for these members inside the compound,
it is sometimes desired to place the documentation block after the member 
instead of before. For this purpose doxygen has the following 
additional comment blocks:
\verbatim
/*!< ... */
\endverbatim
This block can be used to put a Qt style documentation blocks after a member.
The one line version look as follows:
\verbatim
//!< ...
\endverbatim
There are also JavaDoc versions:
\verbatim
/**< ... */
\endverbatim
and
\verbatim
///< ... 
\endverbatim
Note that these blocks have the same structure and meaning as the 
special comment blocks above only the \< indicates that the member is 
located in front of the block instead of after the block.

Here is an example of the use of these comment blocks:
\verbinclude afterdoc.h
 \htmlonly
 Click <a href="$(DOXYGEN_DOCDIR)/examples/afterdoc/html/class_test.html">here</a>
 for the corresponding HTML documentation that is generated by doxygen.
 \endhtmlonly

\warning These blocks can only be used to document \e members.
         They cannot be used to document files, classes, unions, structs,
         groups, namespaces and enums themselves. Furthermore, the structural 
         commands mentioned in the previous section 
         (like <code>\\class</code>) are ignored inside these comment blocks.

\htmlonly
Go to the <a href="lists.html">next</a> section or return to the
 <a href="index.html">index</a>.
\endhtmlonly

*/