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/*!
    \page 21-0-qdoc-configuration.html
    \previouspage Miscellaneous
    \nextpage Generic Configuration Variables

    \title The QDoc Configuration File

    Before running QDoc, you must create a QDoc configuration file to
    tell QDoc where to find the source files that contain the QDoc
    comments. The pathname to your configuration file is passed to
    QDoc on the command line:

    \quotation
        \c {/current/dir$ ../../bin/qdoc ./config.qdocconf}
    \endquotation

    \section1 General Description

    The configuration file is a list of entries of the form \e
    {"variable = value"}. Using the configuration variables, you can
    define where QDoc should find the various source files, images and
    examples, where to put generated documentation etc. The
    configuration file can also contain directives like \c
    include. For an example, see \l {minimal-qdocconf}{a minimal qdocconf file}.

    You can also use configuration variables to get QDoc to support
    \l{Supporting Derived Projects} {derived projects}, i.e QDoc can
    generate links in your project's documentation to elements in the
    Qt online documentation. See the \l {Supporting Derived projects}
    section.

    A valid configuration variable name can include upper and lower case
    letters, numbers, and an underscore, '_'.

    The value of a configuration variable can be set using either '='
    or '+='. The difference is that '=' overrides the previous value,
    while '+=' adds a new value to the current one.

    Values of some configuration variables are interpreted as a list of
    strings, for example:
    \l {sourcedirs-variable}
    {\c{sourcedirs}}, while others are treated as a single string. Double
    quotes around a value string are optional, but including them allows
    you to use special characters like '=' and ' \" ' within the value
    string, for example:

    \badcode
    HTML.postheader = "<a href=\"index.html\">Home</a>"
    \endcode

    If an entry spans many lines, use a backslash at the end of every
    line but the last:

    \badcode
    sourcedirs = kernel tools widgets
    \endcode

    This can be written as:
    \badcode
    sourcedirs = kernel \
                 tools \
                 widgets
    \endcode

    If a value spans multiple lines but is interpreted as a single string,
    the lines are joined with spaces.

    \section1 Expansion of Configuration Values

    QDoc supports expanding environment variables within configuration files.
    For example, Qt modules rely on the environment variable QT_INSTALL_DOCS
    to include definitions related to all Qt module documentation projects:

    \badcode
    include($QT_INSTALL_DOCS/global/qt-module-defaults.qdocconf)
    \endcode

    A variable to expand is prefixed with '$'. To use the literal character
    '$' within a value string, escape it with a backslash: '\\$'.

    Since QDoc 6.0, values can be expanded also from other configuration
    variables. In addition to the \c {$variable} syntax, also \c {${variable}}
    is valid. The latter eliminates the need to separate the variable
    name with whitespace or non-variable characters. For example:

    \badcode
    baseurl = https://doc.qt.io/
    ...
    url = ${baseurl}qtcreator
    \endcode

    If the target variable refers to a list of strings, they will be
    joined using spaces in the expanded value:

    \badcode
    vars = foo \
           bar \
           baz

    items = "Items: $vars"          # Expands to "Items: foo bar baz"
    \endcode

    Controlling which character is used for joining the string list is also
    possible:

    \badcode
    items = "Items: ${vars,|}"      # Expands to "Items: foo|bar|baz"
    items = "Items: ${vars,,}"      # Expands to "Items: foo,bar,baz"
    items = "Items: ${vars,}"       # Expands to "Items: foobarbaz"
    \endcode

    As the expansion is performed after reading in all variables, the order
    in which they are defined does not matter.

    \note Nested variable expansion is not supported.

    \section2 Expanding Environment Variables

    When expanding environment variables, the \c {${variable}} syntax has
    different behavior compared to \c {$variable}. The former expands the
    content of the variable in place to be parsed as part of the
    configuration file, while the latter simply assigns the content as a
    value for the current configuration variable. This has implications if
    the environment variable contains a list of elements separated by
    whitespace, or other formatting recognized by QDoc.

    For example, if the value of an environment variable \c SRCDIRS is
    \c {"../src/a ../src/b"}, then

    \badcode
    sourcedirs  = $SRCDIRS      # Fail - value is interpreted as a single path.
    sourcedirs  = ${SRCDIRS}    # Ok - whitespace is used as a delimiter.
    \endcode

    \section1 Configuration Variables

    \section1 Variable List

    \list
    \li \l {alias-variable} {alias}
    \li \l {Cpp.ignoredirectives-variable} {Cpp.ignoredirectives}
    \li \l {Cpp.ignoretokens-variable} {Cpp.ignoretokens}
    \li \l {defines-variable} {defines}
    \li \l {depends-variable} {depends}
    \li \l {exampledirs-variable} {exampledirs}
    \li \l {examples-variable} {examples}
    \li \l {examples.fileextensions-variable} {examples.fileextensions}
    \li \l {excludedirs-variable} {excludedirs}
    \li \l {excludefiles-variable} {excludefiles}
    \li \l {extraimages-variable} {extraimages}
    \li \l {falsehoods-variable} {falsehoods}
    \li \l {headerdirs-variable} {headerdirs}
    \li \l {headers-variable} {headers}
    \li \l {headers.fileextensions-variable} {headers.fileextensions}
    \li \l {HTML.footer-variable} {HTML.footer}
    \li \l {HTML.postheader-variable} {HTML.postheader}
    \li \l {HTML.style-variable} {HTML.style}
    \li \l {includepaths-variable} {includepaths}
    \li \l {ignorewords-variable} {ignorewords}
    \li \l {ignoresince-variable} {ignoresince}
    \li \l {imagedirs-variable} {imagedirs}
    \li \l {images-variable} {images}
    \li \l {images.fileextensions-variable} {images.fileextensions}
    \li \l {indexes-variable} {indexes}
    \li \l {language-variable} {language}
    \li \l {locationinfo-variable} {locationinfo}
    \li \l {macro-variable} {macro}
    \li \l {manifestmeta-variable} {manifestmeta}
    \li \l {moduleheader-variable} {moduleheader}
    \li \l {navigation-variable} {navigation}
    \li \l {outputdir-variable} {outputdir}
    \li \l {outputformats-variable} {outputformats}
    \li \l {outputprefixes-variable} {outputprefixes}
    \li \l {outputsuffixes-variable} {outputsuffixes}
    \li \l {project-variable} {project}
    \li \l {sourcedirs-variable} {sourcedirs}
    \li \l {sources-variable} {sources}
    \li \l {sources.fileextensions-variable} {sources.fileextensions}
    \li \l {spurious-variable} {spurious}
    \li \l {tabsize-variable} {tabsize}
    \li \l {url-variable} {url}
    \li \l {url.examples-variable} {url.examples}
    \li \l {version-variable} {version}
    \li \l {versionsym-variable} {versionsym}
    \li \l {warninglimit-variable} {warninglimit}
    \endlist

    \section1 Categories

    \list
    \li \l {Generic Configuration Variables}
    \li \l {C++ Specific Configuration Variables}
    \li \l {Format-specific Configuration Variables}
    \endlist

    \section1 Configuration File Examples

    \list
    \li A minimum configuration file: \l minimum.qdocconf
    \li The Qt configuration file: \l qtgui.qdocconf
    \endlist
*/


/*!
    \page 22-qdoc-configuration-generalvariables.html
    \previouspage The QDoc Configuration File
    \nextpage Creating Help Project Files

    \title Generic Configuration Variables

    With the general QDoc configuration variables, you can define
    where QDoc will find the various source files it needs to generate
    the documentation, as well as the directory to put the generated
    documentation. You can also do some minor manipulation of QDoc
    itself, controlling its output and processing behavior.

    \target alias-variable
    \section1 alias

    The \c alias variable renames a QDoc command.

    The general syntax is \tt {alias.\e{original-command-name} = \e
    temporary-command-name}.

    \badcode
        alias.e = i
    \endcode

    This renames the built-in command \\e (italics) to be \\i. The \c
    alias variable is often used for compatibility reasons.

    See also \l {macro-variable} {macro}.

    \target codeindent-variable
    \section1 codeindent

    The \c codeindent variable specifies the level of indentation that
    QDoc uses when writing code snippets.

    QDoc originally used a hard-coded value of four spaces for code
    indentation to ensure that code snippets could be easily
    distinguished from surrounding text. Since we can use \l{HTML
    Specific Configuration Variables#HTML.stylesheets} {stylesheets}
    to adjust the appearance of certain types of HTML elements, this
    level of indentation is not always required.

    \target codeprefix-variable
    \target codesuffix-variable
    \section1 codeprefix, codesuffix

    The \c codeprefix and \c codesuffix variables specify a pair of
    strings that each code snippet is enclosed in.

    \target defines-variable
    \section1 defines

    The \c defines variable specifies the C++ preprocessor symbols
    that QDoc will recognize and respond to.

    When a preprocessor symbol is specified using the \c defines
    variable, you can also use the \l {if-command} {\\if} command to
    enclose documentation that only will be included if the
    preprocessor symbol is defined.

    The values of the variable are regular expressions (see QRegularExpression
    for details). By default, no symbol is defined, meaning that code
    protected with #ifdef...#endif will be ignored.

    \badcode
        defines = Q_QDOC \
                  QT_.*_SUPPORT \
                  QT_.*_LIB \
                  QT_COMPAT \
                  QT3_SUPPORT \
                  Q_OS_.* \
                  Q_BYTE_ORDER \
                  __cplusplus
    \endcode

    This ensures that QDoc will process the code that requires these
    symbols to be defined. For example:

    \code
        #ifdef Q_OS_WIN
          HDC getDC() const;
          void releaseDC(HDC) const;
        #endif
    \endcode

    Since the Q_OS_.* regular expression (specified using the \c
    defines variable) matches Q_OS_WIN, QDoc will process the code
    within #ifdef and #endif in our example.

    You can also define preprocessor symbols manually on the command
    line using the -D option. For example:

    \badcode
        currentdirectory$ qdoc -Dqtforpython qtgui.qdocconf
    \endcode

    In this case the -D option ensures that the \c qtforpython
    preprocessor symbol is defined when QDoc processes the source
    files defined in the qtgui.qdocconf file.

    See also \l {falsehoods-variable} {falsehoods} and \l {if-command} {\\if}.

    \target depends-variable
    \section1 depends

    The \c depends variable defines a list of other documentation projects
    that this project depends on for resolving link targets for type
    inheritance and anything else the documentation needs to link to.

    Like Qt itself, documentation for Qt is distributed across multiple
    modules. In a multi-module documentation project, the minimum set
    of dependencies for a single module consists of actual build
    dependencies. In addition, if there is a documentation project
    (module) that acts as a top-level entry point for the entire
    documentation set and provides \l {navigation-variable}{navigation}
    links, each module documentation should include it as a dependency.

    When QDoc generates documentation for a project, it will also generate
    an \c .index file containing URLs to each linkable entity in the project.
    Each dependency is a (lowercase) name of a project. This name must
    match with the base name of the index file generated for that
    project.

    \badcode
    depends = \
        qtdoc \
        qtcore \
        qtquick
    \endcode

    When invoking QDoc on a project that has dependencies and uses the
    \c depends variable, one or more \c -indexdir path(s) must be passed
    as command line option(s). QDoc uses these paths to search for
    the dependencies' index files.

    \badcode
    qdoc mydoc.qdocconf -outputdir $PWD/html -indexdir $QT_INSTALL_DOCS
    \endcode

    With above, QDoc will search for a file
    \c {$QT_INSTALL_DOCS/qtdoc/qtdoc.index} for a dependency to \c qtdoc.
    If an index file for a dependency is not found, QDoc will output a
    warning.

    The \c depends command accepts also a special value of '*'. This
    instructs QDoc to load all index files found in specified index
    directories; that is, "depends on everything".

    \badcode
    depends = *
    \endcode

    See also \l indexes, \l project, and \l url.

    \target exampledirs-variable
    \section1 exampledirs

    The \c exampledirs variable specifies the directories containing
    the source code of the example files.

    The \l {examples-variable} {examples} and \l
    {exampledirs-variable} {exampledirs} variables are used by the \l
    {quotefromfile-command} {\\quotefromfile}, \l {quotefile-command}
    {\\quotefile} and \l {example-command} {\\example} commands. If
    both the \l {examples-variable} {examples} and \l
    {exampledirs-variable} {exampledirs} variables are defined, QDoc
    will search in both, first in \l {examples-variable} {examples}
    then in \l {exampledirs-variable} {exampledirs}.

    QDoc will search through the directories in the specified order,
    and accept the first matching file it finds. It will only search
    in the specified directories, \e not in subdirectories.

    \badcode
        exampledirs = $QTDIR/doc/src \
                      $QTDIR/examples \
                      $QTDIR \
                      $QTDIR/qmake/examples

        examples    = $QTDIR/examples/widgets/analogclock/analogclock.cpp
    \endcode

    When processing

    \badcode
        \quotefromfile widgets/calculator/calculator.cpp
    \endcode

    QDoc will see if there is a file called \c calculator.cpp
    listed as a value in the \l {examples-variable} {\c examples} variable. If
    there isn't, it will search in the \c exampledirs variable, and
    first see if there exists a file called

    \badcode
        $QTDIR/doc/src/widgets/calculator/calculator.cpp
    \endcode

    If it doesn't, QDoc will continue looking for a file called

    \badcode
        $QTDIR/examples/widgets/calculator/calculator.cpp
    \endcode

    and so forth.

    See also \l {examples-variable}{examples}.

    \target examples-variable
    \section1 examples

    The \c examples variable allows you to specify individual example
    files in addition to those located in the directories specified by
    the \l {exampledirs-variable} {\c exampledirs} variable.

    The \c examples and \l {exampledirs-variable} {\c exampledirs}
    variables are used by the \l {quotefromfile-command}
    {\\quotefromfile}, \l {quotefile-command} {\\quotefile} and \l
    {example-command} {\\example} commands. If both the \c examples and \l
    {exampledirs-variable} {\c exampledirs} variables are defined,
    QDoc will search in both, first in \c examples then in \l
    {exampledirs-variable} {\c exampledirs}.

    QDoc will search through the values listed for the \c examples
    variable, in the specified order, and accept the first one it
    finds.

    For an extensive example, see the \l {exampledirs-variable} {\c
    exampledirs} command. But note that if you know the file is listed
    in the \c examples variable, you don't need to specify its path:

    \badcode
        \quotefromfile calculator.cpp
    \endcode

    See also \l {exampledirs-variable} {exampledirs}.

    \target examples.fileextensions-variable
    \section1 examples.fileextensions

    The \c examples.fileextensions variable specifies the file
    extensions that QDoc will look for when collecting example files
    for display in the documentation.

    The default extensions are *.cpp, *.h, *.js, *.xq, *.svg, *.xml
    and *.ui.

    The extensions are given as standard wildcard expressions. You
    can add a file extension to the filter using '+='. For example:

    \badcode
        examples.fileextensions += *.qrc
    \endcode

    See also \l{headers.fileextensions}.

    \target excludedirs-variable
    \section1 excludedirs

    The \c excludedirs variable is for listing directories that should \e{not}
    be processed by QDoc, even if the same directories are included by the
    \l {sourcedirs-variable} {sourcedirs} or \l {headerdirs-variable} {headerdirs}
    variables.

    For example:

    \badcode
        sourcedirs =  src/corelib
        excludedirs = src/corelib/tmp
    \endcode

    When executed, QDoc will exclude the listed directories from
    further consideration. Files in these directories will not be
    read by QDoc.

    See also \l {excludefiles-variable} {excludefiles}.

    \target excludefiles-variable
    \section1 excludefiles

    The \c excludefiles variable allows you to specify individual files
    that should \e{not} be processed by QDoc.

    \badcode
    excludefiles += $QT_CORE_SOURCES/../../src/widgets/kernel/qwidget.h \
                    $QT_CORE_SOURCES/../../src/widgets/kernel/qwidget.cpp
    \endcode

    If you include the above in your qdocconf file for qtbase, there
    will be no class documentation generated for QWidget.

    Since Qt 5.6, also simple wildcards ('*' and '?') are recognized by
    \c excludefiles. For example, to exclude all private Qt header files
    from being parsed, define the following:

    \badcode
    excludefiles += "*_p.h"
    \endcode

    See also \l {excludedirs-variable} {excludedirs}.

    \target extraimages-variable
    \section1 extraimages

    The \c extraimages variable tells QDoc to incorporate specific
    images in the generated documentation.

    QDoc will not recognize images used within HTML (or any other
    markup language). If we want the images to be copied from the
    directories specified by \l {imagedirs} {\c imagedirs} (the images
    in question must be located in these directories) to the output
    directory, we must specify the images using the \c extraimages
    variable.

    The general syntax is \tt {extraimages.\e{format} = \e image}. The
    file extension is optional.

    For example, in \l qtgui.qdocconf we use a couple of images within
    the HTML.postheader variable which value is pure HTML. For that
    reason, these images are specified using the \c extraimages
    variable:

    \badcode
        extraimages.HTML = qt-logo
    \endcode

    See also \l images and \l imagedirs.

    \target falsehoods-variable
    \section1 falsehoods

    The \c falsehoods variable defines the truth value of specified
    preprocessor symbols as false.

    The values of the variable are regular expressions (see QRegularExpression
    for details). If this variable is not set for a preprocessor
    symbol, QDoc assumes its truth value is true. The exception is
    '0', which is always false.

    QDoc will recognize, and is able to evaluate, the following
    preprocessor syntax:

    \code
        #ifdef NOTYET
         ...
        #endif

        #if defined (NOTYET)
         ...
        #end if
    \endcode

    However, faced with unknown syntax like

    \code
        #if NOTYET
            ...
        #endif
    \endcode

    QDoc will evaluate it as true by default, \e unless the
    preprocessor symbol is specified within the \c falsehoods variable
    entry:

    \badcode
        falsehoods = NOTYET
    \endcode

    See also \l defines.

    \target generateindex-variable
    \section1 generateindex

    The \c generateindex variable contains a boolean value that
    specifies whether to generate an index file when HTML
    documentation is generated.

    By default, an index file is always generated with HTML
    documentation, so this variable is typically only used when
    disabling this feature (by setting the value to \c false) or when
    enabling index generation for the WebXML output (by setting the
    value to \c true).

    \target headerdirs-variable
    \section1 headerdirs

    The \c headerdirs variable specifies the directories containing
    the header files associated with the \c .cpp source files used in
    the documentation.

    \badcode
        headerdirs = $QTDIR/src \
                     $QTDIR/extensions/activeqt \
                     $QTDIR/extensions/motif \
                     $QTDIR/tools/designer/src/lib/extension \
                     $QTDIR/tools/designer/src/lib/sdk \
                     $QTDIR/tools/designer/src/lib/uilib
    \endcode

    When executed, the first thing QDoc will do is to read through the
    headers specified in the \l {headers} {\c headers} variable, and
    the ones located in the directories specified in the \c headerdir
    variable (including all subdirectories), building an internal
    structure of the classes and their functions.

    Then it will read through the sources specified in the \l
    {sources-variable} {\c sources}, and the ones located in the
    directories specified in the \l {sourcedirs-variable} {\c
    sourcedirs} varible (including all subdirectories), merging the
    documentation with the structure it retrieved from the header
    files.

    If both the \c headers and \c headerdirs variables are defined,
    QDoc will read through both, first \l {headers} {\c headers} then
    \c headerdirs.

    In the specified directories, QDoc will only read the files with
    the \c fileextensions specified in the \l {headers.fileextensions}
    {\c headers.fileextensions} variable. The default extensions are
    *.ch, *.h, *.h++, *.hh, *.hpp, and *.hxx". The files specified by
    \l {headers} {\c headers} will be read without taking into account
    their fileextensions.

    See also \l headers and \l headers.fileextensions.

    \target headers-variable
    \section1 headers

    The \c headers variable allows you to specify individual header
    files in addition to those located in the directories specified by
    the \l {headerdirs} {\c headerdirs} variable.

    \badcode
        headers = $QTDIR/src/gui/widgets/qlineedit.h \
                  $QTDIR/src/gui/widgets/qpushbutton.h
    \endcode

    When processing the \c headers variable, QDoc behaves in the same
    way as it does when processing the \l {headerdirs} {\c headerdirs}
    variable. For more information, see the \l {headerdirs} {\c
    headerdirs} variable.

    See also \l headerdirs.

    \target headers.fileextensions-variable
    \section1 headers.fileextensions

    The \c headers.fileextensions variable specify the extension used
    by the headers.

    When processing the header files specified in the \l {headerdirs}
    {\c headerdirs} variable, QDoc will only read the files with the
    fileextensions specified in the \c headers.fileextensions
    variable. In this way QDoc avoids spending time reading irrelevant
    files.

    The default extensions are *.ch, *.h, *.h++, *.hh, *.hpp, and
    *.hxx.

    The extensions are given as standard wildcard expressions. You
    can add a file extension to the filter using '+='. For example:

    \badcode
        header.fileextensions += *.H
    \endcode

    \warning The above assignment may not work as described.

    See also \l headerdirs.

    \target includepaths-variable
    \section1 includepaths

    The \c includepaths variable is used for passing additional
    include paths to the Clang parser that QDoc uses for parsing C++
    code for documentation comments.

    The variable accepts a list of paths, prefixed with \c{-I} (include
    path), \c {-F} (\macos framework include path), or \c{-isystem}
    (system include path). If a prefix is omitted, \c{-I} is used by
    default.

    Paths relative to the current .qdocconf file are resolved into
    absolute paths. Paths that do not exist in the file system are
    ignored.

    \note For Qt documentation projects, the build system typically
          provides the required include paths as command line
          arguments when invoking QDoc.

    See also \l moduleheader.

    \target ignorewords-variable
    \section1 ignorewords

    The \c ignorewords variable is used for specifying a list of strings
    that QDoc will ignore when resolving hyperlink targets.

    QDoc has an auto-linking feature, where linking is attempted for words
    that resemble C++, QML, or JavaScript entities. Specifically, a string
    qualifies for auto-linking if it is at least three characters in
    length, has no whitespace, and it

    \list
      \li is a \e camelCase word, that is, it contains at least one
          uppercase character at index greater than zero, or
      \li contains the substring \c {()} or \c {::}, or
      \li contains at least one special character, \c {@} or \c {_}.
    \endlist

    Adding a qualified word to \c ignorewords stops QDoc from linking
    that word automatically. For example, if the word \e OpenGL is a
    valid link target (a section, \l{page-command}{\\page}, or
    \l {externalpage-command}{\\externalpage} title), a hyperlink for
    each occurrence can be avoided with

    \badcode
    ignorewords += OpenGL
    \endcode

    Linking explicitly with \l {l-command}{\\l} continues to work for
    ignored words.

    The \c ignorewords variable was introduced in QDoc 5.14.

    \target ignoresince-variable
    \section1 ignoresince

    The \c ignoresince variable is used for setting a cutoff value for
    versions passed to the \l {since-command}{\\since} command. All
    \\since commands that define a version lower than the cutoff are
    ignored and do not generate output.

    The cutoff values are project-specific. The project name can be
    defined as a subvariable. The default project name is \e Qt. For
    example:

    \badcode
    ignoresince      = 5.0
    ignoresince.QDoc = 5.0
    \endcode

    These will ignore \\since commands where the major version is 4
    or lower and the project is either \c QDoc or undefined.

    \badcode
    \since 3.2          # Ignored
    \since 5.2          # Documented (as 'Qt 5.2')
    \since QDoc 4.6     # Ignored
    \since QtQuick 2.5  # Documented
    \endcode

    The \c ignoresince variable was introduced in QDoc 5.15.

    See also \l {since-command}{\\since}.

    \target imagedirs-variable
    \section1 imagedirs

    The \c imagedirs variable specifies the directories containing the
    images used in the documentation.

    The \l {images} {\c images} and \c imagedirs variables are used by
    the \l {image-command} {\\image} and \l {inlineimage-command}
    {\\inlineimage} commands. If both the \l {images} {\c images} and
    \c imagedirs variables are defined, QDoc will search in both. First
    in \l {images} {\c images}, then in \c imagedirs.

    QDoc will search through the directories in the specified order,
    and accept the first matching file it finds. It will only search
    in the specified directories, \e not in subdirectories.

    \badcode
        imagedirs = $QTDIR/doc/src/images \
                    $QTDIR/examples

        images    = $QTDIR/doc/src/images/calculator-example.png
    \endcode

    When processing

    \badcode
        \image calculator-example.png
    \endcode

    QDoc will then see if there is a file called
    calculator-example.png listed as a value in the \c images
    variable. If there isn't, it will search in the \c imagedirs
    variable for:

    \badcode
        $QTDIR/doc/src/images/calculator-example.png
    \endcode

    If the file doesn't exist, QDoc will look for a file called

    \badcode
        $QTDIR/examples/calculator-example.png
    \endcode

    You can filter the images in an image directory using the \l
    {images.fileextensions} {\c images.fileextensions} variable. The
    general idea behind the \l {images.fileextensions} {\c images.fileextensions}
    variable is to enable different image format for different output format.

    \warning The \l {images.fileextensions} {\c images.fileextensions}
    variable's functionality is preliminary since QDoc at this point
    only supports HTML.

    See also \l images and \l images.fileextensions.

    \target images-variable
    \section1 images

    The \c images variable allows you to specify individual image
    files in addition to those located in the directories specified by
    the \l {imagedirs} {\c imagedirs} variable.

    \badcode
        images = $QTDIR/doc/src/images/calculator-example.png
    \endcode

    When processing the \c images variable, QDoc behaves in the same
    way as it does when processing the \l {imagedirs} {\c imagedirs}
    variable. For more information, see the \l {imagedirs} {\c
    imagedirs} variable.

    See also \l imagedirs and \l images.fileextensions.

    \target images.fileextensions-variable
    \section1 images.fileextensions

    The images.fileextensions variable filters the files within an
    image directory.

    The variable's values (the extensions) are given as standard
    wildcard expressions. The general syntax is: \tt
    {images.fileextensions.\e{format} = *.\e{extension}}.

    The idea is to enable different image format for different output
    format.

    \badcode
        images.fileextensions.HTML = *.png
        images.fileextensions.LOUT = *.eps
    \endcode

    Then, when processing the \l {image-command} {\\image} and \l
    {inlineimage-command} {\\inlineimage} commands, QDoc will only
    search for files with extensions specified in the variable
    containing the list of output formats.

    \warning This is only a preliminary functionality since QDoc at this
    point only supports HTML.

    The default extensions for HTML are *.png, *.jpg, *.jpeg, and
    *.gif.

    You can add a file extension to the filter using '+='. For
    example:

    \badcode
        images.fileextensions.HTML += *.eps
    \endcode

    See also \l imagedirs and \l images.

    \target language-variable
    \section1 language

    The \c language variable specifies the language of the source code
    that is used in the documentation.

    Currently, C++ is the only language that QDoc understands. It is
    also the default language, and doesn't really need to be
    specified. However, a possible example of a language variable
    statement:

    \badcode
        language = Cpp
    \endcode

    This identifies C++ as the language of the Qt source code.

    \target locationinfo-variable
    \section1 locationinfo

    The \c locationinfo boolean variable determines whether detailed
    location information about each entity is written to
    \c {.index}-files and \c {.webxml}-files (when using the WebXML
    output format).

    Location information consists of the full path and line
    number of either the declaration or documentation comment block
    in the source code.

    Setting this to \c false turns off location info:

    \badcode
        locationinfo = false
    \endcode

    The default value is \c true.

    The \c locationinfo variable was introduced in QDoc 5.15.

    \target macro-variable
    \section1 macro

    The \c macro variable is used to create your own simple QDoc
    commands. The syntax is \tt {macro.\e{command} = \e{definition}},
    where the definition is written using QDoc syntax.

    A macro variable can be restricted for use in one type of output
    generation. By appending \c {.HTML} to the macro name, for
    example, the macro is only used when generating HTML output.

    \badcode
        macro.gui              = "\\b"
        macro.raisedaster.HTML = "<sup>*</sup>"
    \endcode

    The first macro defines the \\gui command to render its argument
    using a bold font. The second macro defines the \\raisedaster
    command to render a superscript asterisk, but only when generating
    HTML.

    A macro can also take up to seven parameters:

    \badcode
    macro.hello            = "Hello \1!"
    \endcode

    Parameters are passed to macros the same way as to other commands:

    \badcode
    \hello World
    \endcode

    When using more than one parameter, or when an argument
    contains whitespace, enclose each argument in braces:

    \badcode
    macro.verinfo          = "\1 (version \2)"
    \endcode

    \badcode
    \verinfo {QFooBar} {1.0 beta}
    \endcode

    A special macro option, \e match, can be added for additional
    regular expression pattern matching for expanded macros.

    For example,

    \badcode
    macro.qtminorversion       = "$QT_VER"
    macro.qtminorversion.match = "\\d+\\.(\\d+)"
    \endcode

    This creates a macro \\qtminorversion that expands to the minor
    version based on the QT_VER environment variable.

    A macro that defines a match pattern outputs all capture groups
    (parentheses) concatenated together, or the exact matched string
    if the pattern does not contain any capture groups.

    See also \l {alias-variable} {alias}.

    \target manifestmeta-variable
    \section1 manifestmeta

    The \c manifestmeta variable specifies additional meta-content
    for the example manifest files generated by QDoc.

    See the \l{Manifest Meta Content} section for more information.

    \target moduleheader-variable
    \section1 moduleheader

    The \c moduleheader variable defines the name of the module
    header of a documented C++ module.

    Projects that document C++ APIs require a module-level header
    that includes all public classes, namespaces and header files
    for the module. The Clang parser in QDoc uses this file to
    build a pre-compiled header (PCH) for the module to increase
    the speed of parsing source files.

    By default, the \l{project-variable}{project} name is used
    also as the module header name.

    \badcode
    project = QtCore
    \endcode

    With the above project name, QDoc searches a module header
    \e QtCore in all known include paths; first using the paths
    passed as command line arguments, then the paths listed in
    the \l includepaths variable.

    QDoc will issue a warning if the module header is not found.
    It will then attempt to build an artificial module header
    based on the headers listed in the \l {headerdirs-variable}
    {headerdirs} variable.

    For Qt documentation projects, the build system typically
    provides QDoc with correct include paths to locate the
    module header, provided that the \c project variable is set
    correctly. The \c moduleheader variable provides an
    alternative file name for QDoc to search for.

    If the project contains no C++ documentation, QDoc should be
    instructed to skip generating a PCH by setting \c moduleheader
    to an empty string:

    \badcode
    # No C++ code to document in this project
    moduleheader =
    \endcode

    See also \l includepaths and \l project.

    \target naturallanguage-variable
    \section1 naturallanguage

    The \c naturallanguage variable specifies the natural language
    used for the documentation generated by QDoc.

    \badcode
        naturallanguage = zh-Hans
    \endcode

    By default, the natural language is \c en for compatibility with
    legacy documentation.

    QDoc will add the natural language information to the HTML it
    generates, using the \c lang and \c xml:lang attributes.

    See also \l {sourceencoding-variable} {sourceencoding},
    \l {outputencoding-variable} {outputencoding},
    \l{http://www.w3.org/TR/xhtml1/#C_7}
    {C.7. The lang and xml:lang Attributes} and
    \l{http://www.w3.org/TR/i18n-html-tech-lang/#ri20040429.113217290}
    {Best Practice 13: Using Hans and Hant codes}.

    \target navigation-variable
    \section1 navigation

    The \c navigation sub-variables, if defined, set the home page, landing
    page, C++ classes page, and QML types page that are visible in the
    generated navigation bar for each page.

    In a project with multiple sub-projects (for example, Qt modules), each
    sub-project typically defines its own landing page while the same home
    page is used across all sub-projects.

    \b Sub-variables

    \table
      \row \li \c navigation.homepage
           \li Project home page.
      \row \li \c navigation.hometitle
           \li (Optional) User-visible title for the home page.
               Default value is taken from \c homepage.
      \row \li \c navigation.landingpage
           \li Sub-project landing page.
      \row \li \c navigation.landingtitle
           \li (Optional) User-visible title for the landing page.
               Defaults value is taken from \c landingpage.
      \row \li \c navigation.cppclassespage
           \li Top-level page that lists all C++ classes for this (sub-)project.
               Typically, the title of a \l {module-command}{\\module} page.
      \row \li \c navigation.cppclassestitle
           \li (Optional) User-visible title for the C++ classes page.
               Default is "C++ Classes".
      \row \li \c navigation.qmltypespage
           \li Top-level page that lists all QML types for this (sub-)project.
               Typically, the title of a \l {qmlmodule-command}{\\qmlmodule} page.
      \row \li \c navigation.qmltypestitle
           \li (Optional) User-visible title for the QML types page.
               Default is "QML Types".
      \row \li \c navigation.toctitles (Since QDoc 6.0)
           \li Page title(s) containing a \l {list-command}{\\list} structure that
               acts as a table of contents (TOC). QDoc generates navigation links
               for pages listed in the TOC, without the need for
               \l {nextpage-command}{\\nextpage} and \l {previouspage-command}
               {\\previouspage} commands.
    \endtable

    For example:

    \badcode
    # Common configuration
    navigation.homepage  = index.html
    navigation.hometitle = "Qt $QT_VER"

    # qtquick.qdocconf
    navigation.landingpage    = "Qt Quick"
    navigation.cppclassespage = "Qt Quick C++ Classes"
    navigation.qmltypespage   = "Qt Quick QML Types"
    \endcode

    The above configuration produces the following navigation bar for \c Item QML type:

    \badcode
    Qt 5.10 > Qt Quick > QML Types > Item QML Type
    \endcode

    \target outputdir-variable
    \section1 outputdir

    The \c outputdir variable specifies the directory where QDoc will
    put the generated documentation.

    \badcode
        outputdir = $QTDIR/doc/html
    \endcode

    locates the generated Qt reference documentation in
    $QTDIR/doc/html. For example, the documentation of the QWidget
    class is located in

    \badcode
        $QTDIR/doc/html/qwidget.html
    \endcode

    The associated images will be put in an \c images subdirectory.

    \warning When running QDoc multiple times using the same output
    directory, all files from the previous run will be lost.

    \target outputencoding-variable
    \section1 outputencoding

    The \c outputencoding variable specifies the encoding used for the
    documentation generated by QDoc.

    \badcode
        outputencoding = UTF-8
    \endcode

    By default, the output encoding is \c ISO-8859-1 (Latin1) for
    compatibility with legacy documentation. When generating
    documentation for some languages, particularly non-European
    languages, this is not sufficient and an encoding such as UTF-8 is
    required.

    QDoc will encode HTML using this encoding and generate the correct
    declarations to indicate to browsers which encoding is being
    used. The \l naturallanguage configuration variable should also be
    specified to provide browsers with a complete set of character
    encoding and language information.

    See also \l outputencoding and \l naturallanguage.

    \target outputformats-variable
    \section1 outputformats

    The \c outputformats variable specifies the format(s) of
    the generated documentation.

    Since Qt 5.11, QDoc supports the HTML and WebXML formats; since
    Qt 5.15, it can also generate the documentation in DocBook. If no
    \c outputformats are specified, QDoc generates the documentation
    in HTML (the default format). All output formats can be specified,
    with dedicated output directories and other settings. For example:

    \badcode
    outputformats = WebXML HTML
    WebXML.nosubdirs = true
    WebXML.outputsubdir = webxml
    WebXML.quotinginformation = true
    \endcode

    This generates HTML documentation using the default settings, as well
    as WebXML documentation into output subdirectory \e webxml.

    \target outputprefixes-variable
    \section1 outputprefixes

    The \c outputprefixes variable specifies a mapping between types of files
    and the prefixes to prepend to the HTML file names in the generated
    documentation.

    \badcode
        outputprefixes     = QML JS
        outputprefixes.QML = uicomponents-
        outputprefixes.JS  = uicomponents-
    \endcode

    By default, files containing the API documentation for QML types
    are prefixed with "qml-", and javaScript types with "js-". In the
    above example, the prefix \c "uicomponents" is used instead for
    both.

    The output prefix is applied to file names for documentation on
    QML and JS types.

    \target outputsuffixes-variable
    \section1 outputsuffixes

    The \c outputsuffixes variable specifies a mapping between types of
    files and module name suffixes to append to the HTML file names.

    \badcode
        outputsuffixes     = QML
        outputsuffixes.QML = -tp
    \endcode

    Given a QML module name \e FooBar and the default
    \l {outputprefixes-variable}{output prefix} ("qml-"), the file name of
    the generated HTML page for a QML type \e FooWidget would be
    \c qml-foobar-tp-foowidget.html.

    By default, no suffix is used. The output suffix, if defined, is applied
    to file names for documentation on QML and JS types, and their respective
    module pages.

    The \c outputsuffixes variable was introduced in QDoc 5.6.

    \target qhp-variable
    \section1 qhp

    The \c qhp variable is used to define the information to be
    written out to Qt Help Project (\c{qhp}) files.

    See the \l{Creating Help Project Files} chapter for information
    about this process.

    \target sourcedirs-variable
    \section1 sourcedirs

    The \c sourcedirs variable specifies the directories containing
    the \c .cpp or \c .qdoc files used in the documentation.

    \badcode
        sourcedirs  += .. \
                       ../../../examples/gui/doc/src
    \endcode

    When executed, the first thing QDoc will do is to read through the
    headers specified in the \l {header-command} {\c header} variable,
    and the ones located in the directories specified in the \c
    headerdir variable (including all subdirectories), building an
    internal structure of the classes and their functions.

    Then it will read through the sources specified in the \l
    {sources} {\c sources}, and the ones located in the directories
    specified in the \l {sourcedirs} {\c sourcedirs} variable
    (including all subdirectories), merging the documentation with the
    structure it retrieved from the header files.

    If both the \c sources and \c sourcedirs variables are defined,
    QDoc will read through both, first \l {sources} {\c sources} then
    \c sourcedirs.

    In the specified directories, QDoc will only read the files with
    the \c fileextensions specified in the \l {sources.fileextensions}
    {\c sources.fileextensions} variable. The default extensions are
    *.c++, *.cc, *.cpp and *.cxx. The files specified by \l {sources}
    {\c sources} will be read independent of their fileextensions.

    See also \l {sources-variable} {sources} and
    \l {sources.fileextensions-variable} {sources.fileextensions}.

    \target sourceencoding-variable
    \section1 sourceencoding

    The \c sourceencoding variable specifies the encoding used for the
    source code and documentation.

    \badcode
        sourceencoding = UTF-8
    \endcode

    By default, the source encoding is \c ISO-8859-1 (Latin1) for
    compatibility with legacy documentation. For some languages,
    particularly non-European languages, this is not sufficient and an
    encoding such as UTF-8 is required.

    Although QDoc will use the encoding to read source and
    documentation files, limitations of C++ compilers may prevent you
    from using non-ASCII characters in source code comments. In cases
    like these, it is possible to write API documentation completely
    in documentation files.

    See also \l {naturallanguage-variable} {naturallanguage} and
    \l {outputencoding-variable} {outputencoding}.

    \target sources-variable
    \section1 sources

    The \c sources variable allows you to specify individual source
    files in addition to those located in the directories specified by
    the \l {sourcedirs-variable} {sourcedirs} variable.

    \badcode
        sources = $QTDIR/src/gui/widgets/qlineedit.cpp \
                  $QTDIR/src/gui/widgets/qpushbutton.cpp
    \endcode

    When processing the \c sources variable, QDoc behaves in the same
    way as it does when processing the \l {sourcedirs-variable}
    {sourcedirs} variable. For more information, see the \l
    {sourcedirs-variable} {sourcedirs} variable.

    See also \l {sourcedirs-variable} {sourcedirs}.

    \target sources.fileextensions-variable
    \section1 sources.fileextensions

    The \c sources.fileextensions variable filters the files within a
    source directory.

    When processing the source files specified in the \l {sourcedirs}
    {\c sourcedirs} variable, QDoc will only read the files with the
    fileextensions specified in the \c sources.fileextensions
    variable. In this way QDoc avoid spending time reading irrelevant
    files.

    The default extensions are *.c++, *.cc, *.cpp and *.cxx.

    The extensions are given as standard wildcard expressions. You
    can add a file extension to the filter using '+='. For example:

    \badcode
        sources.fileextensions += *.CC
    \endcode

    \warning The above assignment may not work as described.

    See also \l {sourcedirs-variable} {sourcedirs} and \l
    (sources-variable} {sources}.


    \target spurious-variable
    \section1 spurious

    The \c spurious variable excludes specified QDoc warnings from the
    output. The warnings are specified using standard wildcard
    expressions.

    \badcode
        spurious = "Cannot find .*" \
        "Missing .*"
    \endcode

    makes sure that warnings matching either of these expressions,
    will not be part of the output when running QDoc. For example
    would the following warning be omitted from the output:

    \badcode
        src/opengl/qgl_mac.cpp:156: Missing parameter name
    \endcode

    \target syntaxhighlighting
    \section1 syntaxhighlighting

    The \c syntaxhighlighting variable specifies whether QDoc should
    perform syntax highlighting on source code quoted in the
    documentation it generates.

    \badcode
        syntaxhighlighting = true
    \endcode

    will enable syntax highlighting for all supported programming
    languages.

    \target tabsize-variable
    \section1 tabsize

    The \c tabsize variable defines the size of a tab character.

    \badcode
    tabsize = 4
    \endcode

    will give the tab character the size of 4 spaces. The default
    value of the variable is 8, and doesn't need to be specified.

    \target tagfile-variable
    \section1 tagfile

    The \c tagfile variable specifies the Doxygen tag file to be
    written when HTML is generated.

    \target version-variable
    \section1 version

    The \c version variable specifies the version number of the
    documented software.

    \badcode
        version = 5.6.0
    \endcode

    When a version number is specified (using the \tt{\l version} or
    \tt {\l versionsym} variables in a \c .qdocconf file), it is
    accessible through the corresponding \\version command for use in
    the documentation.

    \warning The \\version command's functionality is not fully
    implemented; currently it only works within raw HTML code.

    See also \l versionsym.

    \target versionsym-variable
    \section1 versionsym

    The \c versionsym variable specifies a C++ preprocessor symbol
    that defines the version number of the documented software.

    \badcode
        versionsym = QT_VERSION_STR
    \endcode

    QT_VERSION_STR is defined in qglobal.h as follows

    \badcode
        #define QT_VERSION_STR   "5.14.1"
    \endcode

    When a version number is specified (using the \tt{\l version} or
    \tt {\l versionsym} variables in a \c .qdocconf file), it is
    accessible through the corresponding \\version command for use in
    the documentation.

    \warning The \\version command's functionality is not fully
    implemented. Currently, it only works within raw HTML code.

    See also \l {version} {\\version}.

    \target warninglimit-variable
    \section1 warninglimit

    The \c warninglimit variable sets the maximum number of documentation
    warnings allowed. If this limit is exceeded, QDoc continues as normal
    but exits with the warning count as the error code. If the limit was
    not exceeded or \c warninglimit was not defined, QDoc process exits
    with 0, assuming there were no other critical errors.

    Setting the \c warninglimit to \c 0 means failure on any warning.

    \note By default, QDoc does not enforce the warning limit. Enable it
    with \c {warninglimit.enabled = true} or by defining
    the \c QDOC_ENABLE_WARNINGLIMIT environment variable.

    For example,

    \badcode
    # Fail the documentation build if we have more than 100 warnings
    warninglimit = 100
    warninglimit.enabled = true
    \endcode

    The \c warninglimit variable was introduced in Qt 5.11.
*/

/*!
    \page 22-creating-help-project-files.html
    \previouspage Generic Configuration Variables
    \nextpage C++ Specific Configuration Variables

    \title Creating Help Project Files

    \section1 Overview

    Qt Assistant uses a system for managing Qt documentation that requires
    QDoc to generate inventories of files.

    QDoc allows configuration variables to be used to specify which pages are
    to be used in each documentation set it generates. These are specified as
    subvariables of the \c qhp variable with each set declared using a unique
    identifier as a subvariable.

    For example, the configuration file for the Qt Quick documentation set
    specifies information about the set as subvariables with the
    \c{qhp.QtQuick} prefix:

    \badcode
    qhp.projects = QtQuick

    qhp.QtQuick.file                = qtquick.qhp
    qhp.QtQuick.namespace           = org.qt-project.qtquick.$QT_VERSION_TAG
    qhp.QtQuick.virtualFolder       = qtquick
    qhp.QtQuick.indexTitle          = Qt Quick
    qhp.QtQuick.indexRoot           =

    qhp.QtQuick.subprojects         = qmltypes classes examples

    qhp.QtQuick.subprojects.qmltypes.title = QML Types
    qhp.QtQuick.subprojects.qmltypes.indexTitle = Qt Quick QML Types
    qhp.QtQuick.subprojects.qmltypes.selectors = qmlclass
    qhp.QtQuick.subprojects.qmltypes.sortPages = true

    qhp.QtQuick.subprojects.classes.title = Classes
    qhp.QtQuick.subprojects.classes.title = C++ Classes
    qhp.QtQuick.subprojects.classes.indexTitle = Qt Quick C++ Classes
    qhp.QtQuick.subprojects.classes.selectors = class fake:headerfile
    qhp.QtQuick.subprojects.classes.sortPages = true

    qhp.QtQuick.subprojects.examples.title = Examples
    qhp.QtQuick.subprojects.examples.indexTitle = Qt Quick Examples and Tutorials
    qhp.QtQuick.subprojects.examples.selectors = fake:example
    \endcode

    The documentation set may include one or more subprojects, which are added
    to the table of contents under the name specified by \c title. The page
    in the documentation referred to by the \c indexTitle acts as the index page
    for the subproject. The page types to list under the subproject are specified
    by \c selectors. The entries are alphabetically sorted if \c sortPages is set
    to \c true.

    \section2 Using Selectors

    The \c selectors property specifies which page types are listed under the
    table of contents entry for a subproject. Multiple selectors can be listed,
    separated by whitespace.

    \table
    \header \li Selector             \li Description
    \row    \li \c namespace         \li Namespaces
    \row    \li \c class             \li Classes
    \row    \li \c qmltype           \li QML Types
    \row    \li \c qmlclass          \li Alias for \c qmltype.
    \row    \li \c module[:name]     \li C++ modules or members of the module
                                         with a specified name.
    \row    \li \c qmlmodule[:name]  \li QML modules or members of the module
                                         with a specified name.
    \row    \li \c doc[:subtype]     \li Documentation pages with a specified
                                         \c subtype. Multiple subtypes can be
                                         listed as a comma-separated list.
    \row    \li \c fake              \li Alias for \c doc.
    \row    \li \c group[:groupname] \li Documentation pages for members of a
                                         specified group, as added using the
                                         \l {ingroup-command}
                                         {\\ingroup} groupname command.
                                         Multiple group names can be listed as
                                         a comma-separated list.
                                         (Introduced in QDoc 5.6).
    \endtable

    Available subtypes for the \c doc selector:

    \table
    \header \li Subtype              \li Description
    \row    \li \c example           \li Examples
    \row    \li \c headerfile        \li Header files
    \row    \li \c page              \li Documentation pages defined with the
                                         \l {page-command} {\\page} command.
    \endtable

    For example, the following configuration would select example pages and
    pages that include the \c {\ingroup tutorials} command:

    \badcode
    qhp.QtQuickControls.subprojects = examples
    qhp.QtQuickControls.subprojects.examples.title = Examples and Tutorials
    qhp.QtQuickControls.subprojects.examples.indexTitle = Qt Quick Controls Examples
    qhp.QtQuickControls.subprojects.examples.selectors = doc:example group:tutorials
    qhp.QtQuickControls.subprojects.examples.sortPages = true
    \endcode

    \section2 Adding Table of Contents

    To create a table of contents for a manual, create a subproject with
    a \c{type} property and set it to \c{manual}. The page in the documentation
    referred to by the \c{indexTitle} property must contain a list of links
    that acts as a table of contents for the whole manual. QDoc will take the
    information in this list and create a table of contents for the subproject.

    For example, the configuration file for Qt Creator defines only one
    subproject for its documentation, including all the documentation in a
    single manual:

    \badcode
    qhp.QtCreator.subprojects = manual
    qhp.QtCreator.subprojects.manual.title = Qt Creator Manual
    qhp.QtCreator.subprojects.manual.indexTitle = Qt Creator Manual
    qhp.QtCreator.subprojects.manual.type = manual
    \endcode

    In this example, the page entitled "Qt Creator Manual" contains a nested
    list of links to pages in the documentation which is duplicated in
    Qt Assistant's Contents tab.
*/

/*!
    \page 23-qdoc-configuration-cppvariables.html
    \previouspage Creating Help Project Files
    \nextpage Format-specific Configuration Variables

    \title C++ Specific Configuration Variables

    The C++ specific configuration variables are provided to avoid
    erroneous documentation due to non-standard C++ constructs.

    \target Cpp.ignoredirectives-variable
    \section1 Cpp.ignoredirectives
    The \c Cpp.ignoredirectives variable makes QDoc ignore the
    specified non-standard constructs, within C++ source code.

    If not specified by the \tt {\l Cpp.ignoretokens} or \tt {\l
    Cpp.ignoredirectives} variables, non-standard constructs
    (typically macros) can result in erroneous documentation.

    \badcode
    Cpp.ignoredirectives = Q_DECLARE_INTERFACE \
                           Q_DECLARE_OPERATORS_FOR_FLAGS \
                           Q_DECLARE_PRIVATE \
                           Q_DECLARE_PUBLIC \
                           Q_DISABLE_COPY \
                           Q_DUMMY_COMPARISON_OPERATOR \
                           Q_ENUMS \
                           Q_FLAGS \
                           Q_INTERFACES \
                           __attribute__
    \endcode

    makes sure that when processing the code below, for example, QDoc
    will simply ignore the 'Q_ENUMS' and 'Q_FLAGS' expressions:

    \code
        class Q_CORE_EXPORT Qt {
            Q_OBJECT
            Q_ENUMS(Orientation TextFormat BackgroundMode
                    DateFormat ScrollBarPolicy FocusPolicy
                    ContextMenuPolicy CaseSensitivity
                    LayoutDirection ArrowType)
            Q_ENUMS(ToolButtonStyle)
            Q_FLAGS(Alignment)
            Q_FLAGS(Orientations)
            Q_FLAGS(DockWidgetAreas)

          public:
            ...
        };
    \endcode

    The Q_OBJECT macro, however, is an exception: QDoc recognizes this
    particular non-standard construct, so there is no need specifying
    it using the \tt {\l Cpp.ignoredirectives} variable.

    Regarding the Q_CORE_EXPORT macro; see the documentation of the
    \tt {\l Cpp.ignoretokens} variable.

    See also \l Cpp.ignoretokens.

    \target Cpp.ignoretokens-variable
    \section1 Cpp.ignoretokens

    The \c Cpp.ignoretokens variable makes QDoc ignore the specified
    non-standard constructs, within C++ source code.

    If not specified by the \tt {\l Cpp.ignoretokens} or \tt {\l
    Cpp.ignoredirectives} variables, non-standard constructs
    (typically macros) can result in erroneous documentation.

    In \l qtgui.qdocconf:

    \badcode
    Cpp.ignoretokens = QAXFACTORY_EXPORT \
                       QM_EXPORT_CANVAS \
                       ...
                       Q_COMPAT_EXPORT \
                       Q_CORE_EXPORT \
                       Q_EXPLICIT \
                       Q_EXPORT \
                       ...
                       Q_XML_EXPORT
    \endcode

    makes sure that when processing the code below, for example, QDoc
    will simply ignore the 'Q_CORE_EXPORT' expression:

    \code
        class Q_CORE_EXPORT Qt {
            Q_OBJECT
            Q_ENUMS(Orientation TextFormat BackgroundMode
                    DateFormat ScrollBarPolicy FocusPolicy
                    ContextMenuPolicy CaseSensitivity
                    LayoutDirection ArrowType)
            Q_ENUMS(ToolButtonStyle)
            Q_FLAGS(Alignment)
            Q_FLAGS(Orientations)
            Q_FLAGS(DockWidgetAreas)
          public:
            ...
        };
    \endcode

    Regarding the Q_OBJECT, Q_ENUMS and Q_FLAGS macros; see the
    documentation of the \tt {\l Cpp.ignoredirectives} variable.

    See also \l Cpp.ignoredirectives.
*/

/*!
    \page 24-qdoc-configuration-htmlvariables.html
    \previouspage C++ Specific Configuration Variables
    \nextpage Supporting Derived Projects

    \keyword HTML Specific Configuration Variables
    \title Format-specific Configuration Variables

    The format-specific configuration variables define the generated
    documentation's style, or define the contents of the
    documentation's footer or postheader.

    Some of the configuration values are relevant only for the HTML
    output format and their values contain raw HTML.

    \target HTML.footer-variable
    \section1 HTML.footer

    The \c HTML.footer variable defines the content of the generated
    HTML documentation's footer.

    The footer is rendered at the bottom of the generated
    documentation page.

    The variable's value is given as raw HTML code enclosed by
    quotation marks. Note that if the value spans several lines, each
    line needs to be enclosed by quotation marks.

    \badcode
        HTML.footer = "<p /><address><hr /><div align=\"center\">\n" \
                      ...
                      "</tr></table></div></address>"
    \endcode

    \target FORMAT.nosubdirs
    \section1 <FORMAT>.nosubdirs

    A boolean value which, when \c true, enables single-directory output
    mode; all generated files go to \l {FORMAT.outputsubdir} directory,
    instead of a subdirectory based on the documentation project name.

    \target FORMAT.outputsubdir
    \section1 <FORMAT>.outputsubdir

    Defines the subdirectory under \l outputdir where documentation is
    generated.

    \badcode
    HTML.nosubdirs = true
    HTML.outputsubdir = html
    \endcode

    With above, the output goes to \c {<outputdir>/html}.

    \target HTML.postheader-variable
    \section1 HTML.postheader

    The \c HTML.postheader variable defines the content of the
    generated HTML documentation's postheader.

    The header is rendered at the top of the generated documentation
    page.

    The variable's value is given as raw HTML enclosed by quotation
    marks. Note that if the value spans several lines, each line needs
    to be enclosed by quotation marks.

    \badcode
     HTML.postheader = "<table border=\"0\"..." \
                       ...
                       "<img src=\"images/qt-logo.png\" \
                       "align=\"right\" width=\"203\" height=\"32\""\
                      "border=\"0\" />" \
                       "</td></tr>" \
                       "</table>"
    \endcode

    The complete variable entry in \l qtgui.qdocconf provides the
    standard header of the \l {http://doc.qt.io/qt-5/qtgui-index.html}
    {Qt GUI Documentation}.

    \target FORMAT.quotinginformation
    \section1 <FORMAT>.quotinginformation

    A boolean value which, when \c true, generates references to
    quoted content (for example, \l {quotefromfile-command}{\\quotefromfile}
    and \l {snippet-command}{\\snippet} commands) instead of including
    the content directly.

    Used currently for the \c WebXML output format.

    \badcode
    WebXML.quotinginformation = true
    \endcode

    \target HTML.style-variable
    \section1 HTML.style

    The HTML.style variable defines the style for
    the generated HTML documentation.

    The variable's value is given as raw HTML enclosed by quotation
    marks. Note that if the value spans several lines, each line needs
    to be enclosed by quotation marks.

    \badcode
    HTML.style = "h3.fn,span.fn" \
                 "{ margin-left: 1cm; text-indent: -1cm; }\n" \
                 "a:link { color: #004faf; text-decoration: none }\n" \
                 "a:visited" \
                 "{ color: #672967; text-decoration: none }\n" \
                 "td.postheader { font-family: sans-serif }\n" \
                 "tr.address { font-family: sans-serif }\n" \
                 "body { background: #ffffff; color: black; }"
    \endcode

    \target HTML.stylesheets-variable
    \section1 HTML.stylesheets

    The HTML.stylesheets variable defines a list of stylesheets
    to use for the generated HTML documentation.

    Using separate stylesheets for the documentation makes it easier
    to customize and experiment with the style used once the contents
    has been generated. Typically, it is only necessary to define a
    single stylesheet for any set of documentation; for example:

    \badcode
    HTML.stylesheets = path/to/classic.css
    \endcode

    QDoc expects to find stylesheets in the directory containing the
    \l qtgui.qdocconf file, and it will copy those specified to the output
    directory alongside the HTML pages.

    \target HTML.tocdepth
    \section1 <FORMAT>.tocdepth

    The \c {<FORMAT>.tocdepth} variable defines how many document sections
    are printed in the table of contents. Setting tocdepth to \c 0 disables
    the table of contents while leaving it undefined prints all document
    sections.

    Currently only has an effect for the HTML format:

    \badcode
    HTML.tocdepth = 3
    \endcode
*/

/*!
    \page 25-qdoc-configuration-derivedprojects.html
    \previouspage Format-specific Configuration Variables
    \nextpage Example Manifest Files

    \title Supporting Derived Projects

    Some configuration variables allow you to use QDoc to support
    Qt-based projects. They allow your project to contain links to the
    online Qt documentation, which means that QDoc will be able to
    create links to the class reference documentation, without any
    explicit linking command.

    \target description-variable
    \section1 description

    The description variable holds a short description of the
    associated project.

    See also \l project.

    \target indexes-variable
    \section1 indexes

    The \c indexes variable defines a set of paths to index files to load.

    \badcode
    indexes = \
        $QT_INSTALL_DOCS/qtcore/qtcore.index \
        $SOME_OTHER_PROJECT/doc/foo.index
    \endcode

    The \c indexes variable provides an alternative to \l depends for
    defining project's dependencies. As direct paths are provided, no
    \c -indexdir command line option(s) are required when invoking QDoc.

    It is possible to define dependencies using either variable. Qt
    documentation only uses the \c depends variable.

    See also \l depends, \l project and \l url.

    \target project-variable
    \section1 project

    The \c project variable provides a name for the project associated
    with the \c .qdocconf file. This is a mandatory variable that all
    projects must set.

    The project's name is used to form a file name for the associated
    project's \e index file.

    \badcode
        project = QtCreator
    \endcode

    This will cause an index file called \c qtcreator.index to be
    created.

    If the project name contains whitespace or special characters,
    these are replaced with dashes ('-') in the generated index file
    name.

    See also \l depends, \l indexes, and \l description.

    \target url-variable
    \section1 url

    The \c url variable holds the base URL for the
    documentation associated with the current project.

    The URL is stored in the generated index file for the
    project. When we use the index on its own, QDoc will use this as
    the base URL when constructing links to classes, functions, and
    other things listed in the index.

    \badcode
    project     = QtCore
    description = Qt Core Reference Documentation
    url         = https://doc.qt.io/qt/

    ...
    \endcode

    This ensures that whenever QDoc generates
    references to entities in the Qt Core module, the base URL is
    \c https://doc.qt.io/qt/.

    See also \l depends, \l indexes and \l {url.examples}.

    \target url.examples-variable
    \section1 url.examples

    The \c url.examples variable holds the base URL for the examples
    associated with the current project.

    If defined, a link to the example project directory is generated
    at the end of each example documentation page. The \c url.examples
    variable refers to the root directory of the examples related to
    this project; it can be a link to an online repository (starting
    with \e http:// or \e https://), or to the local file system
    (\c file://).

    If \c url.examples is not defined, QDoc will output a list of
    example's files and images instead.

    For example, given these definitions:

    \badcode
    url.examples = "https://code.qt.io/cgit/qt/qtbase.git/tree/examples/"
    examplesinstallpath = corelib
    \endcode

    Then, for the following \l {example-command}{\\example} command:

    \badcode *
    /\1!
        \example threads/semaphores
        ...
    \1/
    \endcode

    QDoc generates a link to
    \c https://code.qt.io/cgit/qt/qtbase.git/tree/examples/corelib/threads/semaphores.

    If the URL contains more components (for example, a query string)
    after the example path, \\1 can be used as a placeholder for the
    path:

    \badcode
    url.examples = "https://code.qt.io/cgit/qt/qtbase.git/tree/examples/\1?h=$QT_VER"
    examplesinstallpath = corelib
    \endcode

    Given the same \\example command as above and assuming that
    \c $QT_VER expands to \c {5.13}, the generated URL is
    \c https://code.qt.io/cgit/qt/qtbase.git/tree/examples/corelib/threads/semaphores?h=5.13.

    \c {url.examples} variable was introduced in QDoc version 5.13.

    See also \l url, \l examplesinstallpath, and \l {example-command}{\\example}.

    \target howto
    \section1 How to Support Derived Projects

    This feature makes use of the comprehensive indexes generated by
    QDoc when it creates the Qt reference documentation.

    For example, \l qtgui.qdocconf (the configuration file for Qt GUI)
    contains the following variable definitions:

    \badcode
        project     = QtGui
        description = Qt GUI Reference Documentation
        url         = http://doc.qt.io/qt/

        ...
    \endcode

    The \l project variable name is used to form a file name for the
    index file; in this case the \c qtgui.index file is created. The \l
    url is stored in the index file. Afterwards, QDoc will use this
    as the base URL when constructing links to classes, functions,
    and other things listed in the index.

    See also \l depends, \l indexes, \l project, and \l url.
*/

/*!
    \page 26-qdoc-configuration-example-manifest-files.html
    \previouspage Supporting Derived Projects

    \title Example Manifest Files

    QDoc generates XML files that contain information about all documented
    examples and demos. These files, named \c {examples-manifest.xml} and
    \c {demos-manifest.xml}, are used by Qt Creator to present a list of
    examples in its welcome screen and to link to their documentation.

    \section1 Manifest XML Structure

    A manifest file has the following structure:

    \badcode
    <?xml version="1.0" encoding="UTF-8"?>
    <instructionals module="QtGui">
        <examples>
            <example
                name="Analog Clock Window Example"
                docUrl="qthelp://org.qt-project.qtgui.502/qtgui/analogclock.html"
                projectPath="gui/analogclock/analogclock.pro"
                imageUrl="qthelp://org.qt-project.qtgui.502/qtgui/images/analogclock-window-example.png">
                <description><![CDATA[The Analog Clock Window example shows how
                    to draw the contents of a custom window.]]></description>
                <tags>analog,clock,window</tags>
                <fileToOpen>gui/analogclock/main.cpp</fileToOpen>
            </example>
            ...
        </examples>
    </instructionals>
    \endcode

    Each \c {<example>} element contains information about a name,
    description, the location of the project file and documentation,
    as well as a list of tags associated with the example.

    \target metacontent
    \section1 Manifest Meta Content

    It is possible to augment the manifest files with additional
    meta-content - that is, extra attributes and tags for selected
    examples, using the \c manifestmeta configuration command.

    One use case for meta-content is highlighting a number of prominent
    examples. Another is improving search functionality by adding
    relevant keywords as tags for a certain category of examples.

    The examples for which meta-content is applied to is specified using
    one or more filters. Matching examples to filters is done based on
    names, with each example name prefixed with a module name and a
    slash. Simple wildcard matching is supported; by using \c {*} at the
    end it's possible to match multiple examples with a single string.

    Example:

    \badcode
    manifestmeta.filters                = highlighted sql webkit global

    manifestmeta.highlighted.names      = "QtGui/Analog Clock Window Example" \
                                          "QtWidgets/Analog Clock Example"
    manifestmeta.highlighted.attributes = isHighlighted:true

    manifestmeta.sql.names              = "QtSql/*"
    manifestmeta.sql.tags               = database,sql

    manifestmeta.webkit.names           = "QtWebKitExamples/*"
    manifestmeta.webkit.tags            = webkit

    manifestmeta.global.names           = *
    manifestmeta.global.tags            = qt5
    \endcode

    Above, an \c isHighlighted attribute is added to two examples. If
    the attribute value is omitted, QDoc uses the string \c {true} by
    default. Extra tags are added for Qt WebKit and Qt SQL examples, and
    another tag is applied to all examples by using just \c {*} as the
    match string.
*/

/*!
    \page 21-1-minimum-qdocconf.html
    \previouspage qtgui.qdocconf
    \nextpage The QDoc Configuration File

    \title minimum.qdocconf

    \quotefile examples/minimum.qdocconf
*/

/*!
    \page 21-2-qtgui-qdocconf.html
    \previouspage Supporting Derived Projects
    \nextpage minimum.qdocconf

    \title qtgui.qdocconf

    \quotefile files/qtgui.qdocconf
*/
