C++ Documentation Style

To generate the documentation, QDoc goes through the source code and generates documentation for C++ types such as classes. QDoc then associates member functions, properties, and other types to the appropriate class.

Note that the documentation must be in the implementation files such as .cpp.

Class Documentation

Class documentation is generated using the \class command and the name of the class as the first argument.

    \class QCache
    \brief The QCache class is a template class that provides a cache.

    \ingroup tools
    \ingroup shared


    QCache\<Key, T\> defines a cache that stores objects of type T
    associated with keys of type Key. For example, here's the
    definition of a cache that stores objects of type Employee
    associated with an integer key:

    \snippet code/doc_src_qcache.cpp 0

    Here's how to insert an object in the cache:

    \snippet code/doc_src_qcache.cpp 1

    ... detailed description ommitted

    \sa QPixmapCache, QHash, QMap

Context commands add information about the class, such as its module or which version the class was added.

Some common context commands are:

  • \brief - the class' brief description (mandatory)
  • \since - the version to which the class was added (mandatory)
  • \internal - marks the class as internal. Internal classes do not appear in the public API documentation.

The Brief and Detailed Description

The brief description is marked with the \brief command and it is for summarizing the purpose or functionality of the class. For C++ classes, QDoc will take the class and create annotated information for the class. The annotated information appears in lists and tables which display the class.

The C++ brief should start with:

"The <C++ class name> class"

The detailed description section starts after the brief description. It provides more information about the class. The detailed description may contain images, snippet code, or links to other relevant documents. There must be an empty line which separates the brief and detailed description.

Member Functions

Typically, function documentation immediately precedes the implementation of the function in the .cpp file. For function documentation that is not immediately above the implementation, the \fn is needed.

  \fn QString &QString::remove(int position, int n)

  Removes \a n characters from the string, starting at the given \a
  position index, and returns a reference to the string.

  If the specified \a position index is within the string, but \a
  position + \a n is beyond the end of the string, the string is
  truncated at the specified \a position.

  \snippet qstring/main.cpp 37

  \sa insert(), replace()
QString &QString::remove(int pos, int len)

The function documentation starts with a verb, indicating the operation the function performs. This also applies to constructors and destructors.

Some common verbs for function documentation:

  • "Constructs..." - for constructors
  • "Destroys..." - for destructors
  • "Returns..." - for accessor functions

The function documentation must document:

  • the return type
  • the parameters
  • the actions of the functions

The \a command marks the parameter in the documentation. The return type documentation should link to the type documentation or be marked with the \c command in the case of boolean values.

    Returns \c true if a QScroller object was already created for \a target; \c false otherwise.

    \sa scroller()
bool QScroller::hasScroller(QObject *target)


The property documentation resides immediately above the read function's implementation. The topic command for properties is \property.

    \property QVariantAnimation::duration
    \brief the duration of the animation

    This property describes the duration in milliseconds of the
    animation. The default duration is 250 milliseconds.

    \sa QAbstractAnimation::duration()
int QVariantAnimation::duration() const

Property documentation usually starts with "This property...", but these are alternate expressions:

  • "This property holds..."
  • "This property describes..."
  • "This property represents..."
  • "Returns true when... and false when..." - for properties that are read.
  • "Sets the..." - for properties that configure a type.

Property documentation must include:

  • description and behavior of the property
  • accepted values for the property
  • the default value of the property

Similar to functions, the default type may be linked or marked with the \c command.

An example of a value range style is:

The values range from 0.0 (no blur) to maximumRadius (maximum blur). By default, the property is set to 0.0 (no blur).

Signals, Notifiers, and Slots

The topic command for signals, notifiers, and slots is \fn. Signal documentation state when they are triggered or emitted.

  \fn QAbstractTransition::triggered()

  This signal is emitted when the transition has been triggered (after
  onTransition() has been called).

Signal documentation typically begin with "This signal is triggered when...". Here are alternate styles:

  • "This signal is triggered when..."
  • "Triggered when..."
  • "Emitted when..."

For slots or notifiers, the condition when they are executed or triggered by a signal should be documented.

  • "Executed when..."
  • "This slot is executed when..."

For properties that have overloaded signals, QDoc groups the overloaded notifiers together. To refer to a specific version of a notifier or signal, simply refer to the property and mention that there are different versions of the notifier.

\property QSpinBox::value
\brief the value of the spin box

setValue() will emit valueChanged() if the new value is different
from the old one. The \l{QSpinBox::}{value} property has a second notifier
signal which includes the spin box's prefix and suffix.

Enums, Namespaces, and Other Types

Enums, namespaces, and macros have a topic command for their documentation:

The language style for these types mention that they are an enum or a macro and continues with the type description.

For enumerations, the \value command is for listing the values. QDoc creates a table of values for the enum.

    \enum QSql::TableType

    This enum type describes types of SQL tables.

    \value Tables  All the tables visible to the user.
    \value SystemTables  Internal tables used by the database.
    \value Views  All the views visible to the user.
    \value AllTables  All of the above.

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