Qt 4.0: QMainWindow Class Reference

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# QMainWindow Class Reference
[QtGui module]

The QMainWindow class provides a main application window. More...

    #include <QMainWindow>

Inherits QWidget.

- List of all members, including inherited members
- Qt 3 support members

### Properties

- iconSize : QSize
- toolButtonStyle : Qt::ToolButtonStyle

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

### Public Functions

- QMainWindow ( QWidget * parent = 0, Qt::WFlags flags = 0 )
- ~QMainWindow ()
- void addDockWidget ( Qt::DockWidgetArea area, QDockWidget * dockwidget )
- void addDockWidget ( Qt::DockWidgetArea area, QDockWidget * dockwidget, Qt::Orientation orientation )
- void addToolBar ( Qt::ToolBarArea area, QToolBar * toolbar )
- void addToolBar ( QToolBar * toolbar )
- QToolBar * addToolBar ( const QString & title )
- void addToolBarBreak ( Qt::ToolBarArea area = Qt::TopToolBarArea )
- QWidget * centralWidget () const
- Qt::DockWidgetArea corner ( Qt::Corner corner ) const
- virtual QMenu * createPopupMenu ()
- Qt::DockWidgetArea dockWidgetArea ( QDockWidget * dockwidget ) const
- QSize iconSize () const
- void insertToolBar ( QToolBar * before, QToolBar * toolbar )
- void insertToolBarBreak ( QToolBar * before )
- QMenuBar * menuBar () const
- void removeDockWidget ( QDockWidget * dockwidget )
- void removeToolBar ( QToolBar * toolbar )
- bool restoreState ( const QByteArray & state, int version = 0 )
- QByteArray saveState ( int version = 0 ) const
- void setCentralWidget ( QWidget * widget )
- void setCorner ( Qt::Corner corner, Qt::DockWidgetArea area )
- void setIconSize ( const QSize & iconSize )
- void setMenuBar ( QMenuBar * menuBar )
- void setStatusBar ( QStatusBar * statusbar )
- void setToolButtonStyle ( Qt::ToolButtonStyle toolButtonStyle )
- void splitDockWidget ( QDockWidget * first, QDockWidget * second, Qt::Orientation orientation )
- QStatusBar * statusBar () const
- Qt::ToolBarArea toolBarArea ( QToolBar * toolbar ) const
- Qt::ToolButtonStyle toolButtonStyle () const

- 184 public functions inherited from QWidget
- 28 public functions inherited from QObject
- 10 public functions inherited from QPaintDevice

### Signals

- void iconSizeChanged ( const QSize & iconSize )
- void toolButtonStyleChanged ( Qt::ToolButtonStyle toolButtonStyle )

- 1 signal inherited from QWidget
- 1 signal inherited from QObject

### Additional Inherited Members

- 17 public slots inherited from QWidget
- 1 public slot 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 QMainWindow class provides a main application window.

QMainWindow provides a main application window, with a menu bar, tool bars, dock widgets and a status bar around a large central widget, such as a text edit, drawing canvas or QWorkspace (for MDI applications).

Topics:

- Saving and restoring state
- Behavior of Dock Widgets

- Dock Widget Separators
- Dragging Dock Widgets
- Dragging over Neighbors
- Dragging over other QDockWidgets
- Dragging to a Different Qt::DockWidgetArea

### Saving and restoring state

The saveState() and restoreState() functions provide a means to save and restore the layout of the QToolBars and QDockWidgets in the QMainWindow. These functions work by storing the objectName of each QToolBar and QDockWidget together with information about placement, size, etc.

### Behavior of Dock Widgets

#### Dock Widget Separators

QMainWindow uses separators to separate QDockWidgets from each other and the central widget. These separators let the user control the size of QDockWidgets by dragging the boundary between them.

A QDockWidget can be as large or as small as the user wishes, between the minimumSizeHint() (or minimumSize()) and maximumSize() of the QDockWidget. When a QDockWidget reaches its minimum size, space will be taken from other QDockWidgets in the direction of the user's drag, if possible. Once all QDockWidgets have reached their minimum sizes, further dragging does nothing. When a QDockWidget reaches its maximium size, space will be given to other QDockWidgets in the opposite direction of the user's drag, if possible. Once all QDockWidgets have reached their minimum size, futher dragging does nothing.

#### Dragging Dock Widgets

QDockWidget displays a title bar to let the user drag the dock widget to a new location. A QDockWidget can be moved to any location provided enough space is available. (QMainWindow won't resize itself to a larger size in an attempt to provide more space.)

A QRubberBand is shown while dragging the QDockWidget. This QRubberBand provides an indication to the user about where the QDockWidget will be placed when the mouse button is released.

#### Dragging over Neighbors

All un-nested QDockWidgets in the same dock area are considered neighbors. When dragging a QDockWidget over its neighbor:

- QMainWindow will split the neighbor perpendicularly to the direction of the QDockWidgets.
- QMainWindow will swap the position of the QDockWidget being dragged and its neighbor once the user has dragged the mouse past the center point of the neighboring QDockWidget.

The following diagram depicts this behavior:

#### Dragging over other QDockWidgets

When dragging nested QDockWidgets, or when dragging to a different dock area, QMainWindow will split the QDockWindow under the mouse. Be aware that the QDockWidget under the mouse will only be split by the QDockWidget being dragged if both can fit in the space currently occupied by the QDockWidget under the mouse.

A QDockWidget can be split horizontally or vertically, with the QDockWidget being dragged being placed in one of four possible locations, as shown in the diagram below:

#### Dragging to a Different Qt::DockWidgetArea

The QDockWidget::floatable property influences feedback when the user drags a QDockWidget over the central widget:

- If floating is `true`, QMainWindow chooses a dock area based on the position of the mouse pointer. If the mouse is within 50 pixels of the central widget's edge, the adjacent dock area is chosen. When dragging into the corners of these 50 pixel regions, the current corner() configuration is used to make the decision. Otherwise, the QRubberBand is shown under the mouse pointer, as above.
- If floating is `false`, QMainWindow chooses a dock area based on the distance between the mouse pointer and the center of the central widget. If the mouse comes within 50 pixels of the central widget's edge, the adjacent dock area is always chosen. When dragging into the corners of these 50 pixel regions, the current corner() configuration is used to make the decision.

In either case, dragging the mouse over another QDockWidget causes QMainWindow to choose the other QDockWidget's dock area.

When dragging outside the QMainWindow, the QDockWidget::floating property again controls feedback during dragging. When the property is `false`, dragging outside of the QMainWindow will show the rubberband over the QDockWidget's current location. This indicates that the QDockWidget cannot be moved outside of the QMainWindow. When the QDockWidget::floatable property is `true`, dragging outside of the QMainWindow will show the QRubberBand under the mouse pointer. This indicates that the QDockWidget will be floating when the mouse button is released.

See also QMenuBar, QToolBar, QStatusBar, and QDockWidget.

## Property Documentation

### iconSize : QSize

This property holds size of toolbar icons in this mainwindow.

The default is the default tool bar icon size of the GUI style.

Access functions:

- QSize iconSize () const
- void setIconSize ( const QSize & iconSize )

### toolButtonStyle : Qt::ToolButtonStyle

This property holds style of toolbar buttons in this mainwindow.

The default is Qt::ToolButtonIconOnly.

Access functions:

- Qt::ToolButtonStyle toolButtonStyle () const
- void setToolButtonStyle ( Qt::ToolButtonStyle toolButtonStyle )

## Member Function Documentation

### QMainWindow::QMainWindow ( QWidget * parent = 0, Qt::WFlags flags = 0 )

Constructs a QMainWindow with the given parent and the specified widget flags.

### QMainWindow::~QMainWindow ()

Destroys the main window.

### void QMainWindow::addDockWidget ( Qt::DockWidgetArea area, QDockWidget * dockwidget )

Adds the given dockwidget to the specified area.

### void QMainWindow::addDockWidget ( Qt::DockWidgetArea area, QDockWidget * dockwidget, Qt::Orientation orientation )

This is an overloaded member function, provided for convenience. It behaves essentially like the above function.

Adds dockwidget into the given area in the direction specified by the orientation.

### void QMainWindow::addToolBar ( Qt::ToolBarArea area, QToolBar * toolbar )

Adds the toolbar into the specified area in this main window. The toolbar is placed at the end of the current tool bar block (i.e. line). If the main window already manages toolbar then it will only move the toolbar to area.

See also insertToolBar(), addToolBarBreak(), and insertToolBarBreak().

### void QMainWindow::addToolBar ( QToolBar * toolbar )

This is an overloaded member function, provided for convenience. It behaves essentially like the above function.

Equivalent of calling addToolBar(Qt::TopToolBarArea, toolbar)

### QToolBar * QMainWindow::addToolBar ( const QString & title )

This is an overloaded member function, provided for convenience. It behaves essentially like the above function.

Creates a QToolBar object, setting its window title to title, and inserts it into the top toolbar area.

See also setWindowTitle().

### void QMainWindow::addToolBarBreak ( Qt::ToolBarArea area = Qt::TopToolBarArea )

Adds a toolbar break to the given area after all the other objects that are present.

### QWidget * QMainWindow::centralWidget () const

Returns the central widget for the main window. This function returns zero if the central widget has not been set.

See also setCentralWidget().

### Qt::DockWidgetArea QMainWindow::corner ( Qt::Corner corner ) const

Returns the dock widget area that occupies the specified corner.

See also setCorner().

### QMenu * QMainWindow::createPopupMenu () `[virtual]`

This function is called to create a popup menu when the user right-clicks on the menu bar, a toolbar or a dock widget. If you want to create a custom popup menu, reimplement this function and return the created popup menu. Ownership of the popup menu is transferred to the caller.

### Qt::DockWidgetArea QMainWindow::dockWidgetArea ( QDockWidget * dockwidget ) const

Returns the Qt::DockWidgetArea for dockwidget.

See also addDockWidget(), splitDockWidget(), and Qt::DockWidgetArea.

### void QMainWindow::iconSizeChanged ( const QSize & iconSize ) `[signal]`

This signal is emitted when the size of the icons used in the window is changed. The new icon size is passed in iconSize.

You can connect this signal to other components to help maintain a consistent appearance for your application.

See also setIconSize().

### void QMainWindow::insertToolBar ( QToolBar * before, QToolBar * toolbar )

Inserts the toolbar into the area occupied by the before toolbar so that it appears before it. For example, in normal left-to-right layout operation, this means that toolbar will appear to the left of the toolbar specified by before in a horizontal toolbar area.

See also insertToolBarBreak(), addToolBar(), and addToolBarBreak().

### void QMainWindow::insertToolBarBreak ( QToolBar * before )

Inserts a toolbar break before the toolbar specified by before.

### QMenuBar * QMainWindow::menuBar () const

Returns the menu bar for the main window. This function creates and returns an empty menu bar if the menu bar does not exist.

See also setMenuBar().

### void QMainWindow::removeDockWidget ( QDockWidget * dockwidget )

Removes the dockwidget from the main window.

### void QMainWindow::removeToolBar ( QToolBar * toolbar )

Removes the toolbar from the main window.

### bool QMainWindow::restoreState ( const QByteArray & state, int version = 0 )

Restores the state of this mainwindow's toolbars and dockwidgets. The version number is compared with that stored in state. If they do not match, the mainwindow's state is left unchanged, and this function returns `false`; otherwise, the state is restored, and this function returns `true`.

See also saveState().

### QByteArray QMainWindow::saveState ( int version = 0 ) const

Saves the current state of this mainwindow's toolbars and dockwidgets. The version number is stored as part of the data.

The objectName property is used to identify each QToolBar and QDockWidget. You should make sure that this property is unique for each QToolBar and QDockWidget you add to the QMainWindow

To restore the saved state, pass the return value and version number to restoreState().

See also restoreState().

### void QMainWindow::setCentralWidget ( QWidget * widget )

Sets the given widget to be the main window's central widget.

Warning: This function should be called at most once for each main window instance

Note: QMainWindow takes ownership of the widget pointer and deletes it at the appropriate time.

See also centralWidget().

### void QMainWindow::setCorner ( Qt::Corner corner, Qt::DockWidgetArea area )

Sets the given dock widget area to occupy the specified corner.

See also corner().

### void QMainWindow::setMenuBar ( QMenuBar * menuBar )

Sets the menu bar for the main window to menuBar.

Note: QMainWindow takes ownership of the menuBar pointer and deletes it at the appropriate time.

See also menuBar().

### void QMainWindow::setStatusBar ( QStatusBar * statusbar )

Sets the status bar for the main window to statusbar.

Note: QMainWindow takes ownership of the statusbar pointer and deletes it at the appropriate time.

See also statusBar().

### void QMainWindow::splitDockWidget ( QDockWidget * first, QDockWidget * second, Qt::Orientation orientation )

Splits the space covered by the first dock widget into two parts, moves the first dock widget into the first part, and moves the second dock widget into the second part.

The orientation specifies how the space is divided: A Qt::Horizontal split places the second dock widget to the right of the first; a Qt::Vertical split places the second dock widget below the first.

Note: The Qt::LayoutDirection influences the order of the dock widgets in the two parts of the divided area. When right-to-left layout direction is enabled, the placing of the dock widgets will be reversed.

### QStatusBar * QMainWindow::statusBar () const

Returns the status bar for the main window. This function creates and returns an empty status bar if the status bar does not exist.

See also setStatusBar().

### Qt::ToolBarArea QMainWindow::toolBarArea ( QToolBar * toolbar ) const

Returns the tool bar area for toolbar.

See also addToolBar(), addToolBarBreak(), and Qt::ToolBarArea.

### void QMainWindow::toolButtonStyleChanged ( Qt::ToolButtonStyle toolButtonStyle ) `[signal]`

This signal is emiited when the style used for tool buttons in the window is changed. The new style is passed in toolButtonStyle.

You can connect this signal to other components to help maintain a consistent appearance for your application.

See also setToolButtonStyle().