QWidgetAction Class

The QWidgetAction class extends QAction by an interface for inserting custom widgets into action based containers, such as toolbars. More...

Header: #include <QWidgetAction>
qmake: QT += widgets
Since: Qt 4.2
Inherits: QAction

This class was introduced in Qt 4.2.

Public Functions

QWidgetAction(QObject *parent)
virtual ~QWidgetAction()
QWidget *defaultWidget() const
void releaseWidget(QWidget *widget)
QWidget *requestWidget(QWidget *parent)
void setDefaultWidget(QWidget *widget)

Protected Functions

virtual QWidget *createWidget(QWidget *parent)
QList<QWidget *> createdWidgets() const
virtual void deleteWidget(QWidget *widget)

Reimplemented Protected Functions

virtual bool event(QEvent *event) override
virtual bool eventFilter(QObject *obj, QEvent *event) override

Detailed Description

Most actions in an application are represented as items in menus or buttons in toolbars. However sometimes more complex widgets are necessary. For example a zoom action in a word processor may be realized using a QComboBox in a QToolBar, presenting a range of different zoom levels. QToolBar provides QToolBar::insertWidget() as convenience function for inserting a single widget. However if you want to implement an action that uses custom widgets for visualization in multiple containers then you have to subclass QWidgetAction.

If a QWidgetAction is added for example to a QToolBar then QWidgetAction::createWidget() is called. Reimplementations of that function should create a new custom widget with the specified parent.

If the action is removed from a container widget then QWidgetAction::deleteWidget() is called with the previously created custom widget as argument. The default implementation hides the widget and deletes it using QObject::deleteLater().

If you have only one single custom widget then you can set it as default widget using setDefaultWidget(). That widget will then be used if the action is added to a QToolBar, or in general to an action container that supports QWidgetAction. If a QWidgetAction with only a default widget is added to two toolbars at the same time then the default widget is shown only in the first toolbar the action was added to. QWidgetAction takes over ownership of the default widget.

Note that it is up to the widget to activate the action, for example by reimplementing mouse event handlers and calling QAction::trigger().

macOS: If you add a widget to a menu in the application's menu bar on macOS, the widget will be added and it will function but with some limitations:

  1. The widget is reparented away from the QMenu to the native menu view. If you show the menu in some other place (e.g. as a popup menu), the widget will not be there.
  2. Focus/Keyboard handling of the widget is not possible.
  3. Due to Apple's design, mouse tracking on the widget currently does not work.
  4. Connecting the triggered() signal to a slot that opens a modal dialog will cause a crash in macOS 10.4 (known bug acknowledged by Apple), a workaround is to use a QueuedConnection instead of a DirectConnection.

See also QAction, QActionGroup, and QWidget.

Member Function Documentation

QWidgetAction::QWidgetAction(QObject *parent)

Constructs an action with parent.

[virtual] QWidgetAction::~QWidgetAction()

Destroys the object and frees allocated resources.

[virtual protected] QWidget *QWidgetAction::createWidget(QWidget *parent)

This function is called whenever the action is added to a container widget that supports custom widgets. If you don't want a custom widget to be used as representation of the action in the specified parent widget then 0 should be returned.

See also deleteWidget().

[protected] QList<QWidget *> QWidgetAction::createdWidgets() const

Returns the list of widgets that have been using createWidget() and are currently in use by widgets the action has been added to.

QWidget *QWidgetAction::defaultWidget() const

Returns the default widget.

See also setDefaultWidget().

[virtual protected] void QWidgetAction::deleteWidget(QWidget *widget)

This function is called whenever the action is removed from a container widget that displays the action using a custom widget previously created using createWidget(). The default implementation hides the widget and schedules it for deletion using QObject::deleteLater().

See also createWidget().

[override virtual protected] bool QWidgetAction::event(QEvent *event)

Reimplements: QAction::event(QEvent *e).

[override virtual protected] bool QWidgetAction::eventFilter(QObject *obj, QEvent *event)

Reimplements: QObject::eventFilter(QObject *watched, QEvent *event).

void QWidgetAction::releaseWidget(QWidget *widget)

Releases the specified widget.

Container widgets that support actions call this function when a widget action is removed.

See also requestWidget(), deleteWidget(), and defaultWidget().

QWidget *QWidgetAction::requestWidget(QWidget *parent)

Returns a widget that represents the action, with the given parent.

Container widgets that support actions can call this function to request a widget as visual representation of the action.

See also releaseWidget(), createWidget(), and defaultWidget().

void QWidgetAction::setDefaultWidget(QWidget *widget)

Sets widget to be the default widget. The ownership is transferred to QWidgetAction. Unless createWidget() is reimplemented by a subclass to return a new widget the default widget is used when a container widget requests a widget through requestWidget().

See also defaultWidget().