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/****************************************************************************
**
** Copyright (C) 2012 Digia Plc and/or its subsidiary(-ies).
** Contact: http://www.qt-project.org/legal
**
** This file is part of the documentation of the Qt Toolkit.
**
** $QT_BEGIN_LICENSE:FDL$
** Commercial License Usage
** Licensees holding valid commercial Qt licenses may use this file in
** accordance with the commercial license agreement provided with the
** Software or, alternatively, in accordance with the terms contained in
** a written agreement between you and Digia. For licensing terms and
** conditions see http://qt.digia.com/licensing. For further information
** use the contact form at http://qt.digia.com/contact-us.
**
** GNU Free Documentation License Usage
** Alternatively, this file may be used under the terms of the GNU Free
** Documentation License version 1.3 as published by the Free Software
** Foundation and appearing in the file included in the packaging of
** this file. Please review the following information to ensure
** the GNU Free Documentation License version 1.3 requirements
** will be met: http://www.gnu.org/copyleft/fdl.html.
** $QT_END_LICENSE$
**
****************************************************************************/
/*!
\class QDesktopWidget
\brief The QDesktopWidget class provides access to screen information on multi-head systems.
\ingroup advanced
\ingroup desktop
Systems with more than one graphics card and monitor can manage the
physical screen space available either as multiple desktops, or as a
large virtual desktop.
This class provides information about the user's desktop, such as its
total size, number of screens, the geometry of each screen, and whether
they are configured as separate desktops or a single virtual desktop.
Widgets provided by Qt use this class to place tooltips, menus and
dialog boxes on the correct screen for their parent or application
widgets. Applications can use this class to obtain information that
can be used to save window positions, or to place child widgets and
dialogs on one particular screen.
\section1 Obtaining a Desktop Widget
The QApplication::desktop() function is used to get an instance of
QDesktopWidget.
The widget's screenGeometry() function provides information about the
geometry of the available screens with. The number of screens
available is returned by screenCount, and the screenCountChanged()
signal is emitted when screens are added or removed.
The screen number that a particular point or widget is located in
is returned by screenNumber().
\section1 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 \e 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.
\section1 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.
\image qdesktopwidget.png Managing Multiple Screens
In the illustration above, Application One's primary screen is
screen 0, and App Two's primary screen is screen 1.
\sa QApplication, QApplication::desktop(), QX11Info::appRootWindow()
*/
/*!
\fn QDesktopWidget::QDesktopWidget()
\internal
Creates the desktop widget.
If the system supports a virtual desktop, this widget will have
the size of the virtual desktop; otherwise this widget will have
the size of the primary screen.
Instead of using QDesktopWidget directly, use QApplication::desktop().
*/
/*!
\fn QDesktopWidget::~QDesktopWidget()
\internal
Destroys the desktop widget and frees any allocated resources.
*/
/*!
\fn int QDesktopWidget::numScreens() const
Returns the number of available screens.
\obsolete
This function is deprecated. Use screenCount instead.
\sa primaryScreen
*/
/*!
\fn QWidget *QDesktopWidget::screen(int screen)
Returns a widget that represents the screen with index \a 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 \a screen.
\sa primaryScreen, screenCount, virtualDesktop
*/
/*!
\fn const QRect QDesktopWidget::availableGeometry(int screen) const
Returns the available geometry of the screen with index \a 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
\a screen is -1.
\note In Symbian devices the available geometry reported by QDesktopWidget is
not guaranteed to be correct at the time the geometry change resize event
is passed to widgets. The correct way to listen for available geometry changes
is to connect to the workAreaResized() signal of QDesktopWidget.
\sa screenNumber(), screenGeometry()
*/
/*!
\fn const QRect QDesktopWidget::availableGeometry(const QWidget *widget) const
\overload
Returns the available geometry of the screen which contains \a widget.
\sa screenGeometry()
*/
/*!
\fn const QRect QDesktopWidget::availableGeometry(const QPoint &p) const
\overload
Returns the available geometry of the screen which contains \a p.
\sa screenGeometry()
*/
/*!
\fn const QRect QDesktopWidget::screenGeometry(int screen) const
Returns the geometry of the screen with index \a screen. The default
screen is used if \a screen is -1.
\note In Symbian devices the screen geometry reported by QDesktopWidget is
not guaranteed to be correct at the time the geometry change resize event
is passed to widgets. The correct way to listen for screen geometry changes
is to connect to the resized() signal of QDesktopWidget.
\sa screenNumber()
*/
/*!
\fn const QRect QDesktopWidget::screenGeometry(const QWidget *widget) const
\overload
Returns the geometry of the screen which contains \a widget.
*/
/*!
\fn const QRect QDesktopWidget::screenGeometry(const QPoint &p) const
\overload
Returns the geometry of the screen which contains \a p.
*/
/*!
\fn int QDesktopWidget::screenNumber(const QWidget *widget) const
Returns the index of the screen that contains the largest
part of \a widget, or -1 if the widget not on a screen.
\sa primaryScreen
*/
/*!
\fn int QDesktopWidget::screenNumber(const QPoint &point) const
\overload
Returns the index of the screen that contains the \a point, or the
screen which is the shortest distance from the \a point.
\sa primaryScreen
*/
/*!
\fn void QDesktopWidget::resizeEvent(QResizeEvent *event)
\reimp
*/
/*!
\fn void QDesktopWidget::resized(int screen)
This signal is emitted when the size of \a screen changes.
*/
/*!
\fn void QDesktopWidget::workAreaResized(int screen)
This signal is emitted when the work area available on \a screen changes.
*/
/*!
\property QDesktopWidget::screenCount
\brief the number of screens currently available on the system.
\since 4.6
\sa screenCountChanged()
*/
/*!
\property QDesktopWidget::primaryScreen
\brief the index of the screen that is configured to be the primary screen
on the system.
*/
/*!
\property QDesktopWidget::virtualDesktop
\brief 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.
*/
/*!
\fn void QDesktopWidget::screenCountChanged(int newCount)
\since 4.6
This signal is emitted when the number of screens changes to \a newCount.
\sa screenCount
*/
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