path: root/doc/faq.doc

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/*! \page faq Frequently Asked Questions

\tableofcontents{html,latex}


\section faq_index How to get information on the index page in HTML?
<p>
You should use the \ref cmdmainpage "\\mainpage" command inside a comment block like this:
\verbatim
/*! \mainpage My Personal Index Page
 *
 * \section intro_sec Introduction
 *
 * This is the introduction.
 *
 * \section install_sec Installation
 *
 * \subsection step1 Step 1: Opening the box
 *  
 * etc...
 */
\endverbatim

\section fac_al Help, some/all of the members of my class / file / namespace are not documented?

  Check the following:
  <ol>
  <li>Is your class / file / namespace documented? If not, it will not 
      be extracted from the sources unless \ref cfg_extract_all "EXTRACT_ALL" is set to \c YES
      in the configuration file.
  <li>Are the members private? If so, you must set \ref cfg_extract_private "EXTRACT_PRIVATE" to \c YES
      to make them appear in the documentation.
  <li>Is there a function macro in your class that does not end with a 
      semicolon (e.g. MY_MACRO())? If so then you have to instruct 
      doxygen's preprocessor to remove it.

      This typically boils down to the following settings in the configuration file:

      \verbatim
ENABLE_PREPROCESSING   = YES
MACRO_EXPANSION        = YES
EXPAND_ONLY_PREDEF     = YES
PREDEFINED             = MY_MACRO()=
      \endverbatim

      Please read the \ref preprocessing "preprocessing" section of the
      manual for more information.
  </ol> 

\section faq_extract_all When I set EXTRACT_ALL to NO none of my functions are shown in the documentation.

In order for global functions, variables, enums, typedefs, and defines 
to be documented you should document the file in which these commands are
located using a comment block containing a \ref cmdfile "\\file" (or \ref cmdfile "\@file") 
command. 

Alternatively, you can put all members in a group (or module)
using the \ref cmdingroup "\\ingroup" command and then document the group using a comment
block containing the \ref cmddefgroup "\\defgroup" command.

For member functions or functions that are part of a namespace you should
document either the class or namespace.
 
\section faq_ext_mapping My file with a custom extension is not parsed (properly) (anymore).

Doxygen only parses files that are specified as input (via the \ref cfg_input "INPUT" tag)
and that match a specified extension (mentioned in \ref cfg_file_patterns "FILE_PATTERNS")
The list of files is then reduced by excluding files listed as \ref cfg_exclude "EXCLUDE" or 
files that match the patterns set by \ref cfg_exclude_patterns "EXCLUDE_PATTERNS".

In the past doxygen parsed all files with an unknown extension as C files which could lead to
undesired results. Since version 1.8.8, doxygen requires that you specify a mapping that tells
for a certain file extension, which parser to use. 
This mapping is specified using the \ref cfg_extension_mapping "EXTENSION_MAPPING" tag.
If no mapping is specified the file's contents will be ignored.

\section faq_code How can I make doxygen ignore some code fragment?

The new and easiest way is to add one comment block 
with a \ref cmdcond "\\cond" command at the start and one comment block 
with a \ref cmdendcond "\\endcond" command at the end of the piece of
code that should be ignored. This should be within the same file of course.

But you can also use doxygen's preprocessor for this: 
If you put
\verbatim
#ifndef DOXYGEN_SHOULD_SKIP_THIS

 /* code that must be skipped by doxygen */

#endif /* DOXYGEN_SHOULD_SKIP_THIS */
\endverbatim
around the blocks that should be hidden and put:
\verbatim
  PREDEFINED = DOXYGEN_SHOULD_SKIP_THIS
\endverbatim
in the configuration file then all blocks should be skipped by doxygen as long
as \ref cfg_enable_preprocessing "ENABLE_PREPROCESSING" is set to `YES`.

\section faq_code_inc How can I change what is after the \#include in the class documentation?

In most cases you can use \ref cfg_strip_from_inc_path "STRIP_FROM_INC_PATH" 
to strip a user defined part of a path.

You can also document your class as follows

\verbatim
/*! \class MyClassName include.h path/include.h
 *
 *  Docs for MyClassName
 */
\endverbatim

To make doxygen put <br><br>
<code>
\#include \<path/include.h\>
</code>

in the documentation of the class MyClassName regardless of the name of the actual 
header file in which the definition of MyClassName is contained.

If you want doxygen to show that the include file should be included using
quotes instead of angle brackets you should type:
\verbatim
/*! \class MyClassName myhdr.h "path/myhdr.h"
 *
 *  Docs for MyClassName
 */
\endverbatim

\section faq_chm How can I use tag files in combination with compressed HTML?

If you want to refer from one compressed HTML file 
\c a.chm to another compressed HTML file 
called \c b.chm, the
link in \c a.chm must have the following format:
\verbatim
<a href="b.chm::/file.html">
\endverbatim
Unfortunately this only works if both compressed HTML files are in the same 
directory.

As a result you must rename the generated \c index.chm files for all projects
into something unique and put all <code>.chm</code> files in one directory.

Suppose you have a project \e a referring to a project \e b using tag file
\c b.tag, then you could rename the \c index.chm for project \e a into
\c a.chm and the \c index.chm for project \e b into \c b.chm. In the 
configuration file for project \e a you write:
\verbatim
TAGFILES = b.tag=b.chm::
\endverbatim

\section faq_html I don't like the quick index that is put above each HTML page, what do I do?

You can disable the index by setting \ref cfg_disable_index "DISABLE_INDEX" to `YES`. Then you can
put in your own header file by writing your own header and feed that to
\ref cfg_html_header "HTML_HEADER".

\section faq_html_header The overall HTML output looks different, while I only wanted to use my own html header file

You probably forgot to include the stylesheet <code>doxygen.css</code> that 
doxygen generates. You can include this by putting
\verbatim
<LINK HREF="doxygen.css" REL="stylesheet" TYPE="text/css">
\endverbatim
in the HEAD section of the HTML page.

\section faq_use_qt Why does doxygen use Qt?

The most important reason is to have a platform abstraction for most 
Unices and Windows by means of the QFile, QFileInfo, QDir, QDate, 
QTime and QIODevice classes. 
Another reason is for the nice and bug free utility classes, like QList, 
QDict, QString, QArray, QTextStream, QRegExp, QXML etc. 

The GUI front-end doxywizard uses Qt for... well... the GUI!

\section faq_excl_dir How can I exclude all test directories from my directory tree?

Simply put an exclude pattern like this in the configuration file:

\verbatim
EXCLUDE_PATTERNS = */test/*
\endverbatim

\section faq_class Doxygen automatically generates a link to the class MyClass somewhere in the running text.  How do I prevent that at a certain place?

Put a \% in front of the class name. Like this: \%MyClass. Doxygen will then
remove the % and keep the word unlinked.

\section faq_pgm_X My favorite programming language is X. Can I still use doxygen?

No, not as such; doxygen needs to understand the structure of what it reads. 
If you don't mind spending some time on it, there are several options:
- If the grammar of X is close to C or C++, then it is probably not too hard to
  tweak \c src/scanner.l a bit so the language is supported. This is done
  for all other languages directly supported by doxygen 
  (i.e. Java, IDL, C#, PHP).
- If the grammar of X is somewhat different than you can write an input
  filter that translates X into something similar enough to C/C++ for
  doxygen to understand (this approach is taken for VB, Object Pascal, and
  JavaScript, see http://www.doxygen.org/download.html#helpers).
- If the grammar is completely different one could write a parser for X and 
  write a backend that produces a similar syntax tree as is done by 
  \c src/scanner.l (and also by \c src/tagreader.cpp while reading tag files).

\section faq_lex Help! I get the cryptic message "input buffer overflow, can't enlarge buffer because scanner uses REJECT"

This error happens when doxygen's lexical scanner has a rule that matches
more than 256K of input characters in one go. I've seen this happening 
on a very large generated file (\>256K lines), where the built-in preprocessor 
converted it into an empty file (with \>256K of newlines). Another case
where this might happen is if you have lines in your code with more than
256K characters. 

If you have run into such a case and want me to fix it, you
should send me a code fragment that triggers the message. To work around
the problem, put some line-breaks into your file, split it up into smaller 
parts, or exclude it from the input using EXCLUDE.

Another way to work around this problem is to use the cmake command with the option:
```
-Denlarge_lex_buffers=<size>
```
where `<size>` is the new size of the input (`YY_BUF_SIZE`) and read (`YY_READ_BUF_SIZE`) buffer.
In case this option is not given the default value of 262144 (i.e. 256K) will be used.

\section faq_latex When running make in the latex directory I get "TeX capacity exceeded". Now what?

You can edit the texmf.cfg file to increase the default values of the 
various buffers and then run "texconfig init".

\section faq_stl Why are dependencies via STL classes not shown in the dot graphs?

Doxygen is unaware of the STL classes, unless the 
option \ref cfg_builtin_stl_support "BUILTIN_STL_SUPPORT" is turned on.

\section faq_search I have problems getting the search engine to work with PHP5 and/or windows

Please read <a href="searching.html">this</a> for hints on where to look. 

\section faq_cmdline Can I configure doxygen from the command line?

Not via command line options, but doxygen can read from <code>stdin</code>,
so you can pipe things through it. Here's an example how to override an option
in a configuration file from the command line (assuming a UNIX like environment):

\verbatim
( cat Doxyfile ; echo "PROJECT_NUMBER=1.0" ) | doxygen -
\endverbatim

For Windows the following would do the same:

\verbatim
( type Doxyfile & echo PROJECT_NUMBER=1.0 ) | doxygen.exe -
\endverbatim

If multiple options with the same name are specified then doxygen will use 
the last one. To append to an existing option you can use the += operator.

\section faq_name How did doxygen get its name?

Doxygen got its name from playing with the words 
documentation and generator.

\verbatim
documentation -> docs -> dox
generator -> gen
\endverbatim

At the time I was looking into \c lex and \c yacc, where a lot of things start with
"yy", so the "y" slipped in and made things pronounceable 
(the proper pronouncement is Docs-ee-gen, so with a long "e").

\section faq_why What was the reason to develop doxygen?

I once wrote a GUI widget based on the Qt library (it is still available at
https://sourceforge.net/projects/qdbttabular/ but hasn't been updated since 2002). 
Qt had nicely generated documentation (using an internal tool which 
<a href="http://rant.gulbrandsen.priv.no/udoc/history">they didn't want to release</a>) 
and I wrote similar docs by hand. 
This was a nightmare to maintain, so I wanted a similar tool. I looked at
Doc++ but that just wasn't good enough (it didn't support signals and
slots and did not have the Qt look and feel I had grown to like), 
so I started to write my own tool...

\htmlonly
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