QMdiArea Class

The QMdiArea widget provides an area in which MDI windows are displayed. More...

Header:	#include <QMdiArea>
qmake:	QT += widgets
Since:	Qt 4.3
Inherits:	QAbstractScrollArea

This class was introduced in Qt 4.3.

• List of all members, including inherited members

Public Types

enum	AreaOption { DontMaximizeSubWindowOnActivation }
flags	AreaOptions
enum	ViewMode { SubWindowView, TabbedView }
enum	WindowOrder { CreationOrder, StackingOrder, ActivationHistoryOrder }

Properties

activationOrder : WindowOrder background : QBrush documentMode : bool tabPosition : QTabWidget::TabPosition

tabShape : QTabWidget::TabShape tabsClosable : bool tabsMovable : bool viewMode : ViewMode

Public Functions

	QMdiArea(QWidget *parent = nullptr)
virtual	~QMdiArea()
QMdiArea::WindowOrder	activationOrder() const
QMdiSubWindow *	activeSubWindow() const
QMdiSubWindow *	addSubWindow(QWidget *widget, Qt::WindowFlags windowFlags = Qt::WindowFlags())
QBrush	background() const
QMdiSubWindow *	currentSubWindow() const
bool	documentMode() const
void	removeSubWindow(QWidget *widget)
void	setActivationOrder(QMdiArea::WindowOrder order)
void	setBackground(const QBrush &background)
void	setDocumentMode(bool enabled)
void	setOption(QMdiArea::AreaOption option, bool on = true)
void	setTabPosition(QTabWidget::TabPosition position)
void	setTabShape(QTabWidget::TabShape shape)
void	setTabsClosable(bool closable)
void	setTabsMovable(bool movable)
void	setViewMode(QMdiArea::ViewMode mode)
QList<QMdiSubWindow *>	subWindowList(QMdiArea::WindowOrder order = CreationOrder) const
QTabWidget::TabPosition	tabPosition() const
QTabWidget::TabShape	tabShape() const
bool	tabsClosable() const
bool	tabsMovable() const
bool	testOption(QMdiArea::AreaOption option) const
QMdiArea::ViewMode	viewMode() const

Reimplemented Public Functions

virtual QSize	minimumSizeHint() const override
virtual QSize	sizeHint() const override

Public Slots

void	activateNextSubWindow()
void	activatePreviousSubWindow()
void	cascadeSubWindows()
void	closeActiveSubWindow()
void	closeAllSubWindows()
void	setActiveSubWindow(QMdiSubWindow *window)
void	tileSubWindows()

Signals

void	subWindowActivated(QMdiSubWindow *window)

Reimplemented Protected Functions

virtual void	childEvent(QChildEvent *childEvent) override
virtual bool	event(QEvent *event) override
virtual bool	eventFilter(QObject *object, QEvent *event) override
virtual void	paintEvent(QPaintEvent *paintEvent) override
virtual void	resizeEvent(QResizeEvent *resizeEvent) override
virtual void	scrollContentsBy(int dx, int dy) override
virtual void	showEvent(QShowEvent *showEvent) override
virtual void	timerEvent(QTimerEvent *timerEvent) override
virtual bool	viewportEvent(QEvent *event) override

Protected Slots

virtual void

setupViewport(QWidget *viewport) override

Detailed Description

QMdiArea functions, essentially, like a window manager for MDI windows. For instance, it draws the windows it manages on itself and arranges them in a cascading or tile pattern. QMdiArea is commonly used as the center widget in a QMainWindow to create MDI applications, but can also be placed in any layout. The following code adds an area to a main window:

    QMainWindow *mainWindow = new QMainWindow;
    mainWindow->setCentralWidget(mdiArea);

Unlike the window managers for top-level windows, all window flags (Qt::WindowFlags) are supported by QMdiArea as long as the flags are supported by the current widget style. If a specific flag is not supported by the style (e.g., the WindowShadeButtonHint), you can still shade the window with showShaded().

Subwindows in QMdiArea are instances of QMdiSubWindow. They are added to an MDI area with addSubWindow(). It is common to pass a QWidget, which is set as the internal widget, to this function, but it is also possible to pass a QMdiSubWindow directly.The class inherits QWidget, and you can use the same API as with a normal top-level window when programming. QMdiSubWindow also has behavior that is specific to MDI windows. See the QMdiSubWindow class description for more details.

A subwindow becomes active when it gets the keyboard focus, or when setFocus() is called. The user activates a window by moving focus in the usual ways. The MDI area emits the subWindowActivated() signal when the active window changes, and the activeSubWindow() function returns the active subwindow.

The convenience function subWindowList() returns a list of all subwindows. This information could be used in a popup menu containing a list of windows, for example.

The subwindows are sorted by the current WindowOrder. This is used for the subWindowList() and for activateNextSubWindow() and activatePreviousSubWindow(). Also, it is used when cascading or tiling the windows with cascadeSubWindows() and tileSubWindows().

QMdiArea provides two built-in layout strategies for subwindows: cascadeSubWindows() and tileSubWindows(). Both are slots and are easily connected to menu entries.

Note: The default scroll bar property for QMdiArea is Qt::ScrollBarAlwaysOff.

See also QMdiSubWindow.

Member Type Documentation

enum QMdiArea::AreaOptionflags QMdiArea::AreaOptions

This enum describes options that customize the behavior of the QMdiArea.

Constant	Value	Description
QMdiArea::DontMaximizeSubWindowOnActivation	0x1	When the active subwindow is maximized, the default behavior is to maximize the next subwindow that is activated. Set this option if you do not want this behavior.

The AreaOptions type is a typedef for QFlags<AreaOption>. It stores an OR combination of AreaOption values.

enum QMdiArea::ViewMode

This enum describes the view mode of the area; i.e. how sub-windows will be displayed.

Constant	Value	Description
QMdiArea::SubWindowView	0	Display sub-windows with window frames (default).
QMdiArea::TabbedView	1	Display sub-windows with tabs in a tab bar.

This enum was introduced or modified in Qt 4.4.

See also setViewMode().

enum QMdiArea::WindowOrder

Specifies the criteria to use for ordering the list of child windows returned by subWindowList(). The functions cascadeSubWindows() and tileSubWindows() follow this order when arranging the windows.

Constant	Value	Description
QMdiArea::CreationOrder	0	The windows are returned in the order of their creation.
QMdiArea::StackingOrder	1	The windows are returned in the order in which they are stacked, with the top-most window being last in the list.
QMdiArea::ActivationHistoryOrder	2	The windows are returned in the order in which they were activated.

See also subWindowList().

Member Function Documentation

QMdiArea::QMdiArea(QWidget *parent = nullptr)

Constructs an empty mdi area. parent is passed to QWidget's constructor.

[slot] void QMdiArea::activateNextSubWindow()

Gives the keyboard focus to another window in the list of child windows. The window activated will be the next one determined by the current activation order.

See also activatePreviousSubWindow() and QMdiArea::WindowOrder.

[slot] void QMdiArea::activatePreviousSubWindow()

Gives the keyboard focus to another window in the list of child windows. The window activated will be the previous one determined by the current activation order.

See also activateNextSubWindow() and QMdiArea::WindowOrder.

[slot] void QMdiArea::cascadeSubWindows()

Arranges all the child windows in a cascade pattern.

See also tileSubWindows().

[slot] void QMdiArea::closeActiveSubWindow()

Closes the active subwindow.

See also closeAllSubWindows().

[slot] void QMdiArea::closeAllSubWindows()

Closes all subwindows by sending a QCloseEvent to each window. You may receive subWindowActivated() signals from subwindows before they are closed (if the MDI area activates the subwindow when another is closing).

Subwindows that ignore the close event will remain open.

See also closeActiveSubWindow().

[slot] void QMdiArea::setActiveSubWindow(QMdiSubWindow *window)

Activates the subwindow window. If window is nullptr, any current active window is deactivated.

See also activeSubWindow().

[override virtual protected slot] void QMdiArea::setupViewport(QWidget *viewport)

Reimplements: QAbstractScrollArea::setupViewport(QWidget *viewport).

This slot is called by QAbstractScrollArea after setViewport() has been called. Reimplement this function in a subclass of QMdiArea to initialize the new viewport before it is used.

See also setViewport().

[signal] void QMdiArea::subWindowActivated(QMdiSubWindow *window)

QMdiArea emits this signal after window has been activated. When window is 0, QMdiArea has just deactivated its last active window, and there are no active windows on the workspace.

See also QMdiArea::activeSubWindow().

[slot] void QMdiArea::tileSubWindows()

Arranges all child windows in a tile pattern.

See also cascadeSubWindows().

[virtual] QMdiArea::~QMdiArea()

Destroys the MDI area.

QMdiSubWindow *QMdiArea::activeSubWindow() const

Returns a pointer to the current active subwindow. If no window is currently active, nullptr is returned.

Subwindows are treated as top-level windows with respect to window state, i.e., if a widget outside the MDI area is the active window, no subwindow will be active. Note that if a widget in the window in which the MDI area lives gains focus, the window will be activated.

See also setActiveSubWindow() and Qt::WindowState.

QMdiSubWindow *QMdiArea::addSubWindow(QWidget *widget, Qt::WindowFlags windowFlags = Qt::WindowFlags())

Adds widget as a new subwindow to the MDI area. If windowFlags are non-zero, they will override the flags set on the widget.

The widget can be either a QMdiSubWindow or another QWidget (in which case the MDI area will create a subwindow and set the widget as the internal widget).

Note: Once the subwindow has been added, its parent will be the viewport widget of the QMdiArea.

    QMdiArea mdiArea;
    QMdiSubWindow *subWindow1 = new QMdiSubWindow;
    subWindow1->setWidget(internalWidget1);
    subWindow1->setAttribute(Qt::WA_DeleteOnClose);
    mdiArea.addSubWindow(subWindow1);

    QMdiSubWindow *subWindow2 =
        mdiArea.addSubWindow(internalWidget2);

When you create your own subwindow, you must set the Qt::WA_DeleteOnClose widget attribute if you want the window to be deleted when closed in the MDI area. If not, the window will be hidden and the MDI area will not activate the next subwindow.

Returns the QMdiSubWindow that is added to the MDI area.

See also removeSubWindow().

[override virtual protected] void QMdiArea::childEvent(QChildEvent *childEvent)

Reimplements: QObject::childEvent(QChildEvent *event).

QMdiSubWindow *QMdiArea::currentSubWindow() const

Returns a pointer to the current subwindow, or nullptr if there is no current subwindow.

This function will return the same as activeSubWindow() if the QApplication containing QMdiArea is active.

See also activeSubWindow() and QApplication::activeWindow().

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

Reimplements: QAbstractScrollArea::event(QEvent *event).

[override virtual protected] bool QMdiArea::eventFilter(QObject *object, QEvent *event)

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

[override virtual] QSize QMdiArea::minimumSizeHint() const

Reimplements: QAbstractScrollArea::minimumSizeHint() const.

[override virtual protected] void QMdiArea::paintEvent(QPaintEvent *paintEvent)

Reimplements: QAbstractScrollArea::paintEvent(QPaintEvent *event).

void QMdiArea::removeSubWindow(QWidget *widget)

Removes widget from the MDI area. The widget must be either a QMdiSubWindow or a widget that is the internal widget of a subwindow. Note widget is never actually deleted by QMdiArea. If a QMdiSubWindow is passed in, its parent is set to nullptr and it is removed; but if an internal widget is passed in, the child widget is set to nullptr and the QMdiSubWindow is not removed.

See also addSubWindow().

[override virtual protected] void QMdiArea::resizeEvent(QResizeEvent *resizeEvent)

Reimplements: QAbstractScrollArea::resizeEvent(QResizeEvent *event).

[override virtual protected] void QMdiArea::scrollContentsBy(int dx, int dy)

Reimplements: QAbstractScrollArea::scrollContentsBy(int dx, int dy).

void QMdiArea::setOption(QMdiArea::AreaOption option, bool on = true)

If on is true, option is enabled on the MDI area; otherwise it is disabled. See AreaOption for the effect of each option.

See also AreaOption and testOption().

[override virtual protected] void QMdiArea::showEvent(QShowEvent *showEvent)

Reimplements: QWidget::showEvent(QShowEvent *event).

[override virtual] QSize QMdiArea::sizeHint() const

Reimplements: QAbstractScrollArea::sizeHint() const.

QList<QMdiSubWindow *> QMdiArea::subWindowList(QMdiArea::WindowOrder order = CreationOrder) const

Returns a list of all subwindows in the MDI area. If order is CreationOrder (the default), the windows are sorted in the order in which they were inserted into the workspace. If order is StackingOrder, the windows are listed in their stacking order, with the topmost window as the last item in the list. If order is ActivationHistoryOrder, the windows are listed according to their recent activation history.

See also WindowOrder.

bool QMdiArea::testOption(QMdiArea::AreaOption option) const

Returns true if option is enabled; otherwise returns false.

See also AreaOption and setOption().

[override virtual protected] void QMdiArea::timerEvent(QTimerEvent *timerEvent)

Reimplements: QObject::timerEvent(QTimerEvent *event).

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

Reimplements: QAbstractScrollArea::viewportEvent(QEvent *event).