QDesktopWidget Class Reference
[QtGui module]

Screen Geometry

To obtain the dimensions of a particular screen, call the screenGeometry() function. On some desktop environments, not all of the screen is available for applications to use; for example, an application dock or menu bar may take up some space. Use the availableGeometry() function to obtain the available area for applications.

QDesktopWidget also inherits the QWidget properties, width() and height(), which specify the size of the desktop. However, for desktops with multiple screens, the size of the desktop is the union of all the screen sizes, so width() and height() should not be used for computing the size of a widget to be placed on one of the screens.

On systems that are configured to use the available screens as a single, large virtual desktop, the virtualDesktop property will be set to true. In this case, the widget's size is usually the size of the bounding rectangle of all the screens.

Use of the Primary Screen

For an application, the screen where the main widget resides is the primary screen. This is stored in the primaryScreen property. All windows opened in the context of the application should be constrained to the boundaries of the primary screen; for example, it would be inconvenient if a dialog box popped up on a different screen, or split over two screens.

In the illustration above, Application One's primary screen is screen 0, and App Two's primary screen is screen 1.

See also QApplication, QApplication::desktop(), and QX11Info::appRootWindow().

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Property Documentation

primaryScreen : const int

This property holds the index of the screen that is configured to be the primary screen on the system.

Access functions:

int	primaryScreen () const

screenCount : const int

This property holds the number of screens currently available on the system.

This property was introduced in Qt 4.6.

Access functions:

int	screenCount () const

Notifier signal:

void	screenCountChanged ( int newCount )

See also screenCountChanged().

virtualDesktop : const bool

This property holds if the system manages the available screens in a virtual desktop.

For virtual desktops, screen() will always return the same widget. The size of the virtual desktop is the size of this desktop widget.

Access functions:

bool	isVirtualDesktop () const

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Member Function Documentation

const QRect QDesktopWidget::availableGeometry ( int screen = -1 ) const

Returns the available geometry of the screen with index screen. What is available will be subrect of screenGeometry() based on what the platform decides is available (for example excludes the dock and menu bar on Mac OS X, or the task bar on Windows). The default screen is used if screen is -1.

See also screenNumber() and screenGeometry().

const QRect QDesktopWidget::availableGeometry ( const QWidget * widget ) const

This is an overloaded function.

Returns the available geometry of the screen which contains widget.

See also screenGeometry().

const QRect QDesktopWidget::availableGeometry ( const QPoint & p ) const

This is an overloaded function.

Returns the available geometry of the screen which contains p.

See also screenGeometry().

void QDesktopWidget::resizeEvent ( QResizeEvent * event )   [virtual protected]

Reimplemented from QWidget::resizeEvent().

void QDesktopWidget::resized ( int screen )   [signal]

This signal is emitted when the size of screen changes.

QWidget * QDesktopWidget::screen ( int screen = -1 )

Returns a widget that represents the screen with index screen (a value of -1 means the default screen).

If the system uses a virtual desktop, the returned widget will have the geometry of the entire virtual desktop; i.e., bounding every screen.

See also primaryScreen, screenCount, and virtualDesktop.

void QDesktopWidget::screenCountChanged ( int newCount )   [signal]

This signal is emitted when the number of screens changes to newCount.

This function was introduced in Qt 4.6.

See also screenCount.

const QRect QDesktopWidget::screenGeometry ( int screen = -1 ) const

Returns the geometry of the screen with index screen. The default screen is used if screen is -1.

See also screenNumber().

const QRect QDesktopWidget::screenGeometry ( const QWidget * widget ) const

This is an overloaded function.

Returns the geometry of the screen which contains widget.

const QRect QDesktopWidget::screenGeometry ( const QPoint & p ) const

This is an overloaded function.

Returns the geometry of the screen which contains p.

int QDesktopWidget::screenNumber ( const QWidget * widget = 0 ) const

Returns the index of the screen that contains the largest part of widget, or -1 if the widget not on a screen.

See also primaryScreen.

int QDesktopWidget::screenNumber ( const QPoint & point ) const

This is an overloaded function.

Returns the index of the screen that contains the point, or the screen which is the shortest distance from the point.

See also primaryScreen.

void QDesktopWidget::workAreaResized ( int screen )   [signal]

This signal is emitted when the work area available on screen changes.