source: trunk/doc/src/qdesktopwidget.qdoc@ 109

/****************************************************************************
**
** Copyright (C) 2009 Nokia Corporation and/or its subsidiary(-ies).
** Contact: Qt Software Information ([email protected])
**
** This file is part of the documentation of the Qt Toolkit.
**
** $QT_BEGIN_LICENSE:LGPL$
** Commercial Usage
** Licensees holding valid Qt Commercial licenses may use this file in
** accordance with the Qt Commercial License Agreement provided with the
** Software or, alternatively, in accordance with the terms contained in
** a written agreement between you and Nokia.
**
** GNU Lesser General Public License Usage
** Alternatively, this file may be used under the terms of the GNU Lesser
** General Public License version 2.1 as published by the Free Software
** Foundation and appearing in the file LICENSE.LGPL included in the
** packaging of this file.  Please review the following information to
** ensure the GNU Lesser General Public License version 2.1 requirements
** will be met: http://www.gnu.org/licenses/old-licenses/lgpl-2.1.html.
**
** In addition, as a special exception, Nokia gives you certain
** additional rights. These rights are described in the Nokia Qt LGPL
** Exception version 1.0, included in the file LGPL_EXCEPTION.txt in this
** package.
**
** GNU General Public License Usage
** Alternatively, this file may be used under the terms of the GNU
** General Public License version 3.0 as published by the Free Software
** Foundation and appearing in the file LICENSE.GPL included in the
** packaging of this file.  Please review the following information to
** ensure the GNU General Public License version 3.0 requirements will be
** met: http://www.gnu.org/copyleft/gpl.html.
**
** If you are unsure which license is appropriate for your use, please
** contact the sales department at [email protected].
** $QT_END_LICENSE$
**
****************************************************************************/

/*!
    \class QDesktopWidget
    \brief The QDesktopWidget class provides access to screen information on multi-head systems.

    \ingroup advanced
    \ingroup desktop
    \ingroup environment
    \mainclass

    QApplication::desktop() function should be used to get an instance
    of the QDesktopWidget.

    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, which usually has the size of the bounding
    rectangle of all the screens (see isVirtualDesktop()). For an
    application, one of the available screens is the primary screen, i.e.
    the screen where the main widget resides (see primaryScreen()). 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.

    The QDesktopWidget provides information about the geometry of the
    available screens with screenGeometry(). The number of screens
    available is returned by numScreens(). The screen number that a
    particular point or widget is located in is returned by
    screenNumber().

    Widgets provided by Qt use this class, for example, to place
    tooltips, menus and dialog boxes according to the parent or
    application widget.

    Applications can use this class to save window positions, or to place
    child widgets on one screen.

    \img 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.

    \target multiple screens note
    \note QDesktopWidget 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. The correct width and height values are obtained using
    availableGeometry() or screenGeometry() for a particular screen.

    \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 bool QDesktopWidget::isVirtualDesktop() const

    Returns true if the system manages the available screens in a
    virtual desktop; otherwise returns false.

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

/*!
    \fn int QDesktopWidget::primaryScreen() const

    Returns the index of the primary screen.

    \sa numScreens()
*/

/*!
    \fn int QDesktopWidget::numScreens() const

    Returns the number of available screens.

    \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(), numScreens(), isVirtualDesktop()
*/

/*!
    \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.

     \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.

    \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.
*/