Topic Commands | QDoc Manual 6.5.1

- Qt 6.5
- QDoc Manual
- Topic Commands
- Qt 6.5.1 Reference Documentation

Command Index ◦ Context Commands

# Topic Commands

A topic command tells QDoc which source code element is being documented. Some topic commands allow you to create documentation pages that aren't tied to any underlying source code element.

When QDoc processes a QDoc comment, it tries to connect the comment to an element in the source code by first looking for a topic command that names the source code element. If there is no topic command, QDoc tries to connect the comment to the source code element that immediately follows the comment. If it can't do either of these and if there is no topic command that indicates the comment does not have an underlying source code element (e.g. \page), then the comment is discarded.

The name of the entity being documented is usually the only argument for a topic command. Use the complete name. Sometimes there can be a second parameter in the argument. See e.g. \page.

     \enum QComboBox::InsertPolicy

The \fn command is a special case. For the \fn command, use the function's signature including the class qualifier.

     \fn void QGraphicsWidget::setWindowFlags(Qt::WindowFlags wFlags)

A topic command can appear anywhere in a comment but must stand alone on its own line. It is good practice is to let the topic command be the first line of the comment. If the argument spans several lines, make sure that each line (except the last one) is ended with a backslash. Moreover, QDoc counts parentheses, which means that if it encounters a '(' it considers everything until the closing ')' as its argument.

If a topic command is repeated with different arguments, the same documentation will appear for both the units.

     /*!
         \fn void PreviewWindow::setWindowFlags()
         \fn void ControllerWindow::setWindowFlags()

         Sets the widgets flags using the QWidget::setWindowFlags()
         function.

         Then runs through the available window flags, creating a text
         that contains the names of the flags that matches the flags
         parameter, displaying the text in the widgets text editor.
     */

The `PreviewWindow::setWindowFlags()` and `ControllerWindow::setWindowFlags()` functions will get the same documentation.

### Nomenclature for files generated by topic commands

For many topic commands, such as \page, QDoc generates a file when processing the documentation.

QDoc normalizes the name of each file before writing it to disk. The following operations are performed:

- All sequences of non alphanumeric characters are replaced with a hyphen, '-'.
- All uppercase letters are replaced with their lowercase equivalent.
- All trailing hyphens are removed.

For example, the following command generates a file named `this-generates-a-file-and-writes-it-to-disk.html`:

     \page this_generates_a_file_(and_writes_it_to_DISK)-.html

As the example shows, the name that is given to the file in the command might differ from the name of the actual file that is written to disk.

#### Prefixes and Suffixes for generated files

When QDoc generates a file, it may add a prefix, a suffix, or both, depending on the element that the file will document.

The table below shows what those prefixes and suffixes are for various elements.

Element | Prefix | Suffix | Command
--- | --- | --- | ---
QML Modules | None | "-qmlmodule" | \qmlmodule
Modules | None | "-module" | \module
Examples | The project name, as given by the project configuration variable, followed by a hyphen. | "-example" | \example
QML Types | The output prefix for QML, as given by the outputprefixes configuration variable. If the module that contains this type is known to QDoc, the module name is added as a prefix, followed by the QML output suffix, as defined by the outputsuffixes configuration variable and a hyphen. | None | \qmltype

## \class

The \class command is for documenting a C++ class. The argument is the complete name of the class. The command tells QDoc that a class is part of the public API, and lets you enter a detailed description.

     /*!
         \class QMap::iterator

         \brief The QMap::iterator class provides an STL-style
         non-const iterator for QMap and QMultiMap.

         QMap features both \l{STL-style iterators} and
         \l{Java-style iterators}. The STL-style iterators ...
     */

The HTML documentation for the named class is written to a `.html` file named from the class name, in lower case, and with the double colon qualifier(s) replaced with '-'. For example, the documentation for the `QMap::Iterator` class is written to `qmap-iterator.html`.

The file contains the class description from the \class comment, plus the documentation generated from QDoc comments for all the class members: a list of the class's types, properties, functions, signals, and slots.

In addition to the detailed description of the class, the \class comment typically contains a \brief command and one or more Markup Commands. See the \class command for any of the Qt class for examples. Here is a very simple example:

     /*!
         \class PreviewWindow
         \brief The PreviewWindow class is a custom widget.
                displaying the names of its currently set
                window flags in a read-only text editor.

         \ingroup miscellaneous

         The PreviewWindow class inherits QWidget. The widget
         displays the names of its window flags set with the \l
         {function} {setWindowFlags()} function. It is also
         provided with a QPushButton that closes the window.

         ...

         \sa QWidget
     */

The way QDoc renders this \class will depend a lot on your `style.css` file, but the general outline of the class reference page will look like this:

> # PreviewWindow Class Reference

> The PreviewWindow class is a custom widget displaying the names of its currently set window flags in a read-only text editor. More...

> ### Properties

> - 52 properties inherited from QWidget
> - 1 property inherited from QObject

> ### Public Functions

> - PreviewWindow(QWidget *parent = 0)
> - void setWindowFlags(Qt::WindowFlags flags)
> - 183 public functions inherited from QWidget
> - 28 public functions inherited from QObject

> ### Public Slots

> - 17 public slots inherited from QWidget
> - 1 public slot inherited from QObject

> ### Additional Inherited Members

> - 1 signal inherited from QWidget
> - 1 signal inherited from QObject
> - 4 static public members inherited from QWidget
> - 4 static public members inherited from QObject
> - 39 protected functions inherited from QWidget
> - 7 protected functions inherited from QObject

> ## Detailed Description

> The PreviewWindow class is a custom widget displaying the names of its currently set window flags in a read-only text editor.

> The PreviewWindow class inherits QWidget. The widget displays the names of its window flags set with the setWindowFlags() function. It is also provided with a QPushButton that closes the window.

> ...

> See also QWidget.

> ## Member Function Documentation

> ### PreviewWindow(QWidget *parent = 0)

> Constructs a preview window widget with parent.

> ### setWindowFlags(Qt::WindowFlags flags)

> Sets the widgets flags using the QWidget::setWindowFlags() function.

> Then runs through the available window flags, creating a text that contains the names of the flags that matches the flags parameter, displaying the text in the widgets text editor.

## \enum

The \enum command is for documenting a C++ enum type. The argument is the full name of the enum type.

The enum values are documented in the \enum comment using the \value command. If an enum value is not documented with \value, QDoc emits a warning. These warnings can be avoided using the \omitvalue command to tell QDoc that an enum value should not be documented. The enum documentation will be included on the class reference page, header file page, or namespace page where the enum type is defined. For example, consider the enum type `Corner` in the Qt namespace:

     enum Corner {
         TopLeftCorner = 0x00000,
         TopRightCorner = 0x00001,
         BottomLeftCorner = 0x00002,
         BottomRightCorner = 0x00003
     #if defined(QT3_SUPPORT) && !defined(Q_MOC_RUN)
         ,TopLeft = TopLeftCorner,
         TopRight = TopRightCorner,
         BottomLeft = BottomLeftCorner,
         BottomRight = BottomRightCorner
     #endif
     };

This enum can be cocumented this way:

     /*!
         \enum Qt::Corner

         This enum type specifies a corner in a rectangle:

         \value TopLeftCorner
                The top-left corner of the rectangle.
         \value TopRightCorner
                The top-right corner of the rectangle.
         \value BottomLeftCorner
                The bottom-left corner of the rectangle.
         \value BottomRightCorner
                The bottom-right corner of the rectangle.

         \omitvalue TopLeft
         \omitvalue TopRight
         \omitvalue BottomLeft
         \omitvalue BottomRight
                    Bottom-right (omitted; not documented).
     */

Note the inclusion of the namespace qualifier. QDoc will render this enum type in `qt.html` like this:

> ### enum Qt::Corner

> This enum type specifies a corner in a rectangle:

> Constant | Value | Description
> --- | --- | ---
> `Qt::TopLeftCorner` | `0x00000` | The top-left corner of the rectangle.
> `Qt::TopRightCorner` | `0x00001` | The top-right corner of the rectangle.
> `Qt::BottomLeftCorner` | `0x00002` | The bottom-left corner of the rectangle.
> `Qt::BottomRightCorner` | `0x00003` | The bottom-right corner of the rectangle.

See also \value and \omitvalue.

## \example

The \example command is for documenting an example. The argument is the example's path relative to one of the paths listed in the exampledirs variable in the QDoc configuration file.

The documentation page will be output to `modulename-path-to-example`.html. QDoc will add a list of all the example's source and images files at the end of the page, unless \noautolist command is used or the configuration variable url.examples is defined for the project.

For example, if exampledirs contains `$QTDIR/examples/widgets/imageviewer`, then

     /*!
         \example widgets/imageviewer
         \title ImageViewer Example
         \subtitle

         The example shows how to combine QLabel and QScrollArea
         to display an image.

         ...
     */

QDoc renders this example in widgets-imageviewer.html:

> # Image Viewer Example

> The example shows how to combine QLabel and QScrollArea to display an image.

> Files:

> - widgets/imageviewer/imageviewer.cpp
> - widgets/imageviewer/imageviewer.h
> - widgets/imageviewer/main.cpp

> ...

See also: \noautolist, url.examples, \meta

## \externalpage

The \externalpage command assigns a title to an external URL.

     /*!
         \externalpage http://doc.qt.io/
         \title Qt Documentation Site
     */

This allows you to include a link to the external page in your documentation this way:

     /*!
         At the \l {Qt Documentation Site} you can find the latest
         documentation for Qt, Qt Creator, the Qt SDK and much more.
     */

QDoc renders this as:

> At the Qt Documentation Site you can find the latest documentation for Qt, Qt Creator, the Qt SDK and much more.

To achieve the same result without using the \externalpage command, you would have to hard-code the address into your documentation:

     /*!
         At the \l {http://doc.qt.io/}{Qt Documentation Site}
         you can find the latest documentation for Qt, Qt Creator, the Qt SDK
         and much more.
     */

The \externalpage command makes it easier to maintain the documentation. If the address changes, you only need to change the argument of the \externalpage command.

## \fn (function)

The \fn command is for documenting a function. The argument is the function's signature, including its template parameters (if any), return type, const-ness, and list of formal arguments with types. If the named function doesn't exist, QDoc emits a warning.

Since QDoc version 6.0, the \fn command can be used for documenting class members that are not explicitly declared in the header, but are implicitly generated by the compiler; default constructor and destructor, copy constructor and move-copy constructor, assignment operator, and move-assignment operator.

When documenting an hidden friend, it is required to prepend the enclosing class name to the function name. For example, for:

     class Foo {
        ...
        friend bool operator==(const Foo&, const Foo&) { ... }
        ...
     }

The command should be written as `"\fn Foo::operator==(const Foo&, const Foo&)"` and not as the free function `"\fn operator==(const Foo&, const Foo&)"`.

Failure to do so will have QDoc complaining about being unable to resolve the function.

Note: The \fn command is QDoc's default command: when no topic command can be found in a QDoc comment, QDoc tries to tie the documentation to the following code as if it is the documentation for a function. Hence, it is normally not necessary to include this command when documenting a function, if the function's QDoc comment is written immediately above the function implementation in the `.cpp` file. But it must be present when documenting an inline function in the `.cpp` file that is implemented in the `.h` file.

     /*!
         \fn bool QToolBar::isAreaAllowed(Qt::ToolBarArea area) const

         Returns \c true if this toolbar is dockable in the given
         \a area; otherwise returns \c false.
     */

QDoc renders this as:

> ### bool QToolBar::isAreaAllowed(Qt::ToolBarArea area) const

> Returns `true` if this toolbar is dockable in the given area; otherwise returns `false`.

Note: Running in debug mode (pass the `-debug` command line option or set the `QDOC_DEBUG` environment variable before invoking QDoc) can help troubleshoot \fn commands that QDoc fails to parse. In debug mode, additional diagnostic information is available.

See also \overload.

## \group

The \group command creates a separate page that lists the classes belonging to the group. The argument is the group name.

A class is included in a group by using the \ingroup command. Overview pages can also be related to a group using the same command, but the list of overview pages must be requested explicitly using the \generatelist command (see example below).

The \group command is typically followed by a \title command and a short introduction to the group. The HTML page for the group is written to an `.html` file named <lower-case-group-name>.html.

Each class name is listed as a link to the class reference page followed by the text from the class's \brief texts.

     /*!
         \group io

         \title Input/Output and Networking

         These classes are used to handle input and output to
         and from external devices, processes, files etc., as
         well as manipulating files and directories.
     */

QDoc generates a group page in `io.html` that will look like this:

> # Input/Output and Networking

> These classes are used to handle input and output to and from external devices, processes, files etc., as well as manipulating files and directories.

> QAbstractSocket | The base functionality common to all socket types
> QBuffer | QIODevice interface for a QByteArray
> QClipboard | Access to the window system clipboard

Note that overview pages related to the group, must be listed explicitly using the \generatelist command with the `related` argument.

     /*!
         \group architecture

         \title Architecture

         These documents describe aspects of Qt's architecture
         and design, including overviews of core Qt features and
         technologies.

         \generatelist{related}
     */

See also \ingroup and \generatelist.

## \headerfile

The \headerfile command is for documenting the global functions, types and macros that are declared in a header file, but not in a namespace. The argument is the name of the header file. The HTML page is written to a `.html` file constructed from the header file argument.

The documentation for a function, type, or macro that is declared in the header file being documented, is included in the header file page using the \relates command.

If the argument doesn't exist as a header file, the \headerfile command creates a documentation page for the header file anyway.

     /*!
        \headerfile <QtAlgorithms>

        \title Generic Algorithms

        \brief The <QtAlgorithms> header file provides
         generic template-based algorithms.

        Qt provides a number of global template functions in \c
        <QtAlgorithms> that work on containers and perform
        well-know algorithms.
     */

QDoc generates a header file page `qtalgorithms.html` that looks like this:

> # <QtAlgorithms> - Generic Algorithms

> The header file provides generic template-based algorithms. More...

> ### Functions

> - RandomAccessIterator qBinaryFind (RandomAccessIterator begin, RandomAccessIterator end, const T & value)
> - ...

> ## Detailed Description

> The header file provides generic template-based algorithms.

> Qt provides a number of global template functions in `<QtAlgorithms>` that work on containers and perform well-know algorithms.

> ...

See also \inheaderfile.

## \macro

The \macro command is for documenting a C++ macro. The argument is the macro in one of three styles: function-like macros like Q_ASSERT(), declaration-style macros like Q_PROPERTY(), and macros without parentheses like Q_OBJECT.

The \macro comment must contain a \relates command that attaches the macro comment to a class, header file, or namespace. Otherwise, the documentation will be lost. Here are three example macro comments followed by what they might look like in `qtglobal.html` or `qobject.html`:

     /*!
         \macro void Q_ASSERT(bool test)
         \relates <QtGlobal>

         Prints a warning message containing the source code
         file name and line number if \a test is false.

         ...

         \sa Q_ASSERT_X(), qFatal(), {Debugging Techniques}
     */

> ### void Q_ASSERT ( bool test )

> Prints a warning message containing the source code file name and line number if test is false.

> ...

> See also Q_ASSERT_X(), qFatal() and Debugging Techniques.

     /*!
         \macro Q_PROPERTY(...)
         \relates QObject

         This macro declares a QObject property. The syntax is:

         ...

         \sa {Qt's Property System}
     */

> ### Q_PROPERTY ( ... )

> This macro declares a QObject property. The syntax is:

> ...

> See also Qt's Property System.

     /\1!
         \macro Q_OBJECT
         \relates QObject

         The Q_OBJECT macro must appear in the private section
         of a class definition that declares its own signals and
         slots, or that uses other services provided by Qt's
         meta-object system.

         ...

         \sa {Meta-Object System}, {Signals and Slots}, {Qt's
         Property System}
     \1/

> ### Q_OBJECT

> The Q_OBJECT macro must appear in the private section of a class definition that declares its own signals and slots or that uses other services provided by Qt's meta-object system.

> ...

> See also Meta-Object System, Signals & Slots and Qt's Property System.

## \module

The \module creates a page that lists the classes belonging to the module specified by the command's argument. A class included in the module by including the \inmodule command in the \class comment.

The \module command is typically followed by a \title and a \brief command. Each class is listed as a link to the class reference page followed by the text from the class's \brief command. For example:

     /*!
         \module QtNetwork

         \title Qt Network Module

         \brief Contains classes for writing TCP/IP clients and servers.

         The network module provides classes to make network
         programming easier and portable. It offers both
         high-level classes such as QNetworkAccessManager that
         implements application-level protocols, and
         lower-level classes such as QTcpSocket, QTcpServer, and
         QUdpSocket.
     */

QDoc renders this in `qtnetwork.html` like this:

> #
> Qt Network Module

> The Qt Network module offers classes that allow you to write TCP/IP clients and servers.More...

> QAbstractSocket | The base functionality common to all socket types
> ... | ...

> ## Detailed Description

> The Qt Network module offers classes that allow you to write TCP/IP clients and servers.

> The network module provides classes to make network programming easier and portable. It offers both high-level classes such as QNetworkAccessManager that implements application-level protocols, and lower-level classes such as QTcpSocket, QTcpServer, and QUdpSocket.

> ...

The \noautolist command can be used here to omit the automatically generated list of classes at the end.

See also \inmodule

## \namespace

The \namespace command is for documenting the contents of the C++ namespace named as its argument. The reference page QDoc generates for a namespace is similar to the reference page it generates for a C++ class.

     /*!
         \namespace Qt

         \brief Contains miscellaneous identifiers used throughout the Qt library.
     */

QDoc renders this in `qt.html` like this:

> # Qt Namespace

> The Qt namespace contains miscellaneous identifiers used throughout the Qt library. More...

>     #include <Qt>

> - Obsolete members

> ### Types

> - flags Alignment
> - ...

> ## Detailed Description

> Contains miscellaneous identifiers used throughout the Qt library.

> ...

Note that in C++, a particular namespace can be used in more than one module, but when C++ elements from different modules are declared in the same namespace, the namespace itself must be documented in one module only. For example, namespace Qt in the example above contains types and functions from both QtCore and QtGui, but it is documented with the \namespace command only in QtCore.

## \page

The \page command is for creating a stand-alone documentation page.

The \page command expects a single argument that represents the name of the file where QDoc should store the page.

The page title is set using the \title command.

     /*!
        \page aboutqt.html

        \title About Qt

        Qt is a C++ toolkit for cross-platform GUI
        application development. Qt provides single-source
        portability across Microsoft Windows, macOS, Linux,
        and all major commercial Unix variants.

        Qt provides application developers with all the
        functionality needed to build applications with
        state-of-the-art graphical user interfaces. Qt is fully
        object-oriented, easily extensible, and allows true
        component programming.

        ...
     */

QDoc renders this page in `aboutqt.html`.

## \property

The \property command is for documenting a Qt property. The argument is the full property name.

A property is defined using the Q_PROPERTY() macro. The macro takes as arguments the property's name and its set, reset and get functions.

     Q_PROPERTY(QString state READ state WRITE setState)

The set, reset and get functions don't need to be documented, documenting the property is sufficient. QDoc will generate a list of the access function that will appear in the property documentation which in turn will be located in the documentation of the class that defines the property.

The \property command comment typically includes a \brief command. For properties the \brief command's argument is a sentence fragment that will be included in a one line description of the property. The command follows the same rules for the description as the \variable command.

     /*!
         \property QPushButton::flat
         \brief Whether the border is disabled.

         This property's default is false.
     */

QDoc includes this in `qpushbutton.html` like this:

> ### flat : bool

> This property holds whether the border is disabled.

> This property's default is false.

> Access functions:

> - bool isFlat () const
> - void setFlat ( bool )

     /*!
         \property QWidget::width
         \brief The width of the widget excluding any window frame.

         See the \l {Window Geometry} documentation for an
         overview of window geometry.

         \sa geometry, height, size
     */

QDoc includes this in `qwidget.html` like this:

> ### width : const int

> This property holds the width of the widget excluding any window frame.

> See the Window Geometry documentation for an overview of window geometry.

> Access functions:

> - int width () const

> See also geometry, height, and size.

## \qmlattachedproperty

The \qmlattachedproperty command is for documenting a QML property that will be attached to some QML type. See Attached Properties. The argument is the rest of the line. The argument text should be the property type, followed by the QML element name where the property is being declared, the `::` qualifier, and finally the property name. If we have a QML attached property named `isCurrentItem` in QML `ListView`, and the property has type `bool`, the \qmlattachedproperty for it would look like this:

     /*!
         \qmlattachedproperty bool ListView::isCurrentItem

         This attached property is \c true if this delegate is the current
         item; otherwise false.

         It is attached to each instance of the delegate.

         This property may be used to adjust the appearance of the current
         item, for example:

         \snippet doc/src/snippets/declarative/listview/listview.qml isCurrentItem
     */

QDoc includes this attached property on the QML reference page for the ListView type.

## \qmlattachedsignal

The \qmlattachedsignal command is for documenting an attachable signal. The \qmlattachedsignal command is used just like the \qmlsignal command.

The argument is the rest of the line. It should be the name of the QML type where the signal is declared, the `::` qualifier, and finally the signal name. For example, a QML attached signal named `add()` in the `GridView` element is documented like this:

     /*!
         \qmlattachedsignal GridView::add()
         This attached signal is emitted immediately after an item is added to the view.
     */

QDoc includes this documentation on the QML reference page for the GridView element.

## \qmlvaluetype

The \qmlvaluetype command is for documenting a value type for QML. The argument is the type name. The type must be included in the QML value types group using the \ingroup command as shown below. This will cause QDoc to include the documentation for the type on the QML Value Types page. The \brief command is also required, because it appears on the QML Value Types page as well.

     /*!
         \qmlvaluetype int
         \ingroup qmlvaluetypes

         \brief An integer is a whole number, for example 0, 10, or -20.

         An integer is a whole number, e.g. 0, 10, or -20. The possible
         \c int values range from around -2000000000 to around
         2000000000, although most elements will only accept a reduced
         range (which they mention in their documentation).

         Example:
         \qml
         Item { width: 100; height: 200 }
         \endqml

         \sa {QML Value Types}
     */

QDoc outputs this as qml-int.html.

## \qmlclass

This command is deprecated. Use \qmltype instead.

The \qmlclass command is for documenting a QML type that is instantiated by a C++ class. The command has two arguments. The first argument is the name of the QML type. The second argument is the name of the C++ class that instantiates the QML type.

     /*!
         \qmlclass Transform QGraphicsTransform
         \ingroup qml-transform-elements
         \since 4.7
         \brief Provides a way of building advanced transformations on Items.

         The Transform element is a base type which cannot be
         instantiated directly. The following concrete Transform types
         are available:

         \list
           \li \l Rotation
           \li \l Scale
           \li \l Translate
         \endlist

         The Transform elements let you create and control advanced
         transformations that can be configured independently using
         specialized properties.

         You can assign any number of Transform elements to an \l
         Item. Each Transform is applied in order, one at a time.
     */

This example generates the QML Transform page. The \qmlclass comment should include the \since command, because all QML types are new. It should also include the \brief command. If a type is a member of a group of QML types, it should also include one or more \ingroup commands.

## \qmlmethod

The \qmlmethod command is for documenting a QML method. The argument is the complete method signature, including return type and parameter names and types.

     /*!
         \qmlmethod void TextInput::select(int start, int end)

         Causes the text from \a start to \a end to be selected.

         If either start or end is out of range, the selection is not changed.

         After having called this, selectionStart will become the lesser, and
         selectionEnd the greater (regardless of the order passed to this method).

        \sa selectionStart, selectionEnd
     */

QDoc includes this documentation on the element reference page for the TextInput element.

## \qmltype

The \qmltype command is for documenting a QML type. The command has one argument, which is the name of the QML type.

If the QML type is instantiated by a C++ class, that class must be specified using the \instantiates context command.

     /*!
         \qmltype Transform
         \instantiates QGraphicsTransform
         \inqmlmodule QtQuick

         \brief Provides a way to build advanced transformations on Items.

         The Transform element is a base type which cannot be
         instantiated directly.
     */

Here, the \qmltype comment includes \instantiates to specify that a Transform is instantiated by the C++ class QGraphicsTransform. A \qmltype comment should always include a \since command, because all QML types are new. It should also include a \brief description. If a QML type is a member of a QML type group, the \qmltype comment should include one or more \ingroup commands.

## \qmlproperty

The \qmlproperty command is for documenting a QML property. The argument is the rest of the line. The argument text should be the property type, followed by the QML type name, the `::` qualifier, and finally the property name. If we have a QML property named `x` in QML type `Translate`, and the property has type `real`, the \qmlproperty for it would look like this:

     /*!
         \qmlproperty real Translate::x

         The translation along the X axis.
     */

QDoc includes this QML property on the QML reference page for the Translate type.

If the QML property is of enumeration type, or it holds a bit-wise combination of flags, the \value command can be used to document the acceptable values.

## \qmlsignal

The \qmlsignal command is for documenting a QML signal. The argument is the rest of the line. The arguments should be: the QML type where the signal is declared, the `::` qualifier, and finally the signal name. If we have a QML signal named `clicked()`, the documentation for it would look like this:

     /*!
         \qmlsignal QtQuick::MouseArea::clicked(MouseEvent mouse)

         This signal is emitted when there is a click. A click is defined as a
         press followed by a release, both inside the MouseArea.
     */

QDoc includes this documentation on the QML reference page for the MouseArea type.

## \qmlmodule

Use the `\qmlmodule` command to create a `QML` module page. A QML module page is a collection of QML types or any related material. The command takes an optional `<VERSION>` number argument, and is similar to the group-command.

A QML type is associated with a module by adding the \inqmlmodule command to the comment-block that documents the type. You can link to any member of a QML module using the module name and two colons (`::`) prefix.

     /*!
         A link to the TabWidget of the UI Component is \l {UIComponent::TabWidget}.
     */

QDoc generates a page for the module that lists all the members of the module.

     /*!
         \qmlmodule ClickableComponents

         This is a list of the Clickable Components set. A Clickable component
         responds to a \c clicked() event.
     */

## \inqmlmodule

A QML class may belong to a QML module by inserting the \inqmlmodule command as a topic command, with the module name (without a version number) as the only argument. Every member of a group must be linked to using the module name and two colons (`::`).

     /*!
         \qmltype ClickableButton
         \inqmlmodule ClickableComponents

         A clickable button that responds to the \c click() event.
     */

To link to the `ClickableButton`, use the `\l ClickableComponents::ClickableButton` format.

The \noautolist command can be used here to omit the automatically generated list of types at the end.

## \instantiates

The \instantiates command is used in the QML type comment of an elemental QML type to specify the name of the C++ class that instantiates the QML type.

If the QML type is not instantiated by a C++ class, this command is not used.

     /*!
         \qmltype Transform
         \instantiates QGraphicsTransform
         \inqmlmodule QtQuick

         \brief Provides a way to build advanced transformations on Items.

         The Transform element is a base type which cannot be
         instantiated directly.
     */

Here, the \qmltype comment includes \instantiates to specify that a Transform is instantiated by the C++ class QGraphicsTransform.

## \typealias

The \typealias command is similar to \typedef, but specific to documenting a C++ type alias:

     class Foo
     {
     public:
         using ptr = void*;
     // ...
     }

This can be documented as

     /*!
         \typealias Foo::ptr
     */

QDoc will automatically generate a sentence in the documentation describing the alias:

> This is a type alias for `void*`.

The \typealias command was introduced in QDoc 5.15.

See also \typedef.

## \typedef

The \typedef command is for documenting a C++ typedef. The argument is the name of the typedef. The documentation for the typedef will be included in the reference documentation for the class, namespace, or header file in which the typedef is declared. To relate the \typedef to a class, namespace, or header file, the \typedef comment must contain a \relates command.

     /*!
         \typedef QObjectList
         \relates QObject

         Synonym for QList<QObject>.
     */

QDoc includes this in `qobject.html` as:

> ### typedef QObjectList

> Synonym for QList<QObject>.

Another, although more rare, example:

     /*!
         \typedef QMsgHandler
         \relates QtGlobal

         This is a typedef for a pointer to a function with the
         following signature:

         \code
             void myMsgHandler(QtMsgType, const char *);
         \endcode

         \sa QtMsgType, qInstallMessageHandler()
     */

QDoc includes this in `qtglobal.html` as:

> ### typedef QtMsgHandler

> This is a typedef for a pointer to a function with the following signature:

> `

>         void myMsgHandler(QtMsgType, const char *);

> `

> See also QtMsgType and qInstallMessageHandler().

Other typedefs are located on the reference page for the class that defines them.

     /*!
         \typedef QList::Iterator

         Qt-style synonym for QList::iterator.
     */

QDoc includes this one on the reference page for class QList as:

> ### typedef QList::Iterator

> Qt-style synonym for QList::iterator.

See also \typealias.

## \variable

The \variable command is for documenting a class member variable or a constant. The argument is the variable or constant name. The \variable command comment includes a \brief command. QDoc generates the documentation based on the text from \brief command.

The documentation will be located in the in the associated class, header file, or namespace documentation.

In case of a member variable:

     /*!
         \variable QStyleOption::palette
         \brief The palette that should be used when painting
                the control
     */

QDoc includes this in qstyleoption.html as:

> ### QPalette QStyleOption::palette

> This variable holds the palette that should be used when painting the control.

You can also document constants with the \variable command. For example, suppose you have the `Type` and `UserType` constants in the QTreeWidgetItem class:

     enum { Type = 0, UserType = 1000 };

For these, the \variable command can be used this way:

     /*!
         \variable QTreeWidgetItem::Type

         The default type for tree widget items.

         \sa UserType, type()
     */

     /*!
         \variable QTreeWidgetItem::UserType

         The minimum value for custom types. Values below
         UserType are reserved by Qt.

         \sa Type, type()
     */

QDoc includes these in qtreewidget.html as:

> ### const int QTreeWidgetItem::Type

> The default type for tree widget items.

> See also UserType and type().

> ### const int QTreeWidgetItem::UserType

> The minimum value for custom types. Values below UserType are reserved by Qt.

> See also Type and type().

Command Index ◦ Context Commands