gui/kernel/qsessionmanager.cpp

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#include <qsessionmanager.h>
#include <qguiapplication.h>
#include <qpa/qplatformsessionmanager.h>
#include <qpa/qplatformintegration.h>

#include <private/qobject_p.h>
#include <private/qguiapplication_p.h>
#include <private/qsessionmanager_p.h>

#ifndef QT_NO_SESSIONMANAGER

QT_BEGIN_NAMESPACE

/*!
    \class QSessionManager
    \brief The QSessionManager class provides access to the session manager.

    \inmodule QtGui

    A session manager in a desktop environment (in which Qt GUI applications
    live) keeps track of a session, which is a group of running applications,
    each of which has a particular state. The state of an application contains
    (most notably) the documents the application has open and the position and
    size of its windows.

    The session manager is used to save the session, e.g., when the machine is
    shut down, and to restore a session, e.g., when the machine is started up.
    We recommend that you use QSettings to save an application's settings,
    for example, window positions, recently used files, etc. When the
    application is restarted by the session manager, you can restore the
    settings.

    QSessionManager provides an interface between the application and the
    platform's session manager. In Qt, session management requests for action
    are handled by the two signals QGuiApplication::commitDataRequest() and
    QGuiApplication::saveStateRequest(). Both provide a reference to a
    QSessionManager object as argument. The session manager can only be
    accessed in slots invoked by these signals.

    \warning If you use QSessionManager, you should disable fallback session
    management: QGuiApplication::setFallbackSessionManagementEnabled().

    No user interaction is possible \e unless the application gets explicit
    permission from the session manager. You ask for permission by calling
    allowsInteraction() or, if it is really urgent, allowsErrorInteraction().
    Qt does not enforce this, but the session manager may.

    You can try to abort the shutdown process by calling cancel().

    For sophisticated session managers provided on Unix/X11, QSessionManager
    offers further possibilities to fine-tune an application's session
    management behavior: setRestartCommand(), setDiscardCommand(),
    setRestartHint(), setProperty(), requestPhase2(). See the respective
    function descriptions for further details.

    \sa QGuiApplication, {Session Management}
*/


/*! \enum QSessionManager::RestartHint

    This enum type defines the circumstances under which this application wants
    to be restarted by the session manager. The current values are:

    \value  RestartIfRunning    If the application is still running when the
                                session is shut down, it wants to be restarted
                                at the start of the next session.

    \value  RestartAnyway       The application wants to be started at the
                                start of the next session, no matter what.
                                (This is useful for utilities that run just
                                after startup and then quit.)

    \value  RestartImmediately  The application wants to be started immediately
                                whenever it is not running.

    \value  RestartNever        The application does not want to be restarted
                                automatically.

    The default hint is \c RestartIfRunning.
*/

QSessionManagerPrivate::QSessionManagerPrivate(const QString &id,
                                               const QString &key)
    : QObjectPrivate()
{
    if (qApp->testAttribute(Qt::AA_DisableSessionManager)) {
        platformSessionManager = new QPlatformSessionManager(id, key);
    } else {
        platformSessionManager = QGuiApplicationPrivate::platformIntegration()->createPlatformSessionManager(id, key);
    }
    Q_ASSERT_X(platformSessionManager, "Platform session management",
               "No platform session management, should use the default implementation");
}

QSessionManagerPrivate::~QSessionManagerPrivate()
{
    delete platformSessionManager;
    platformSessionManager = nullptr;
}

QSessionManager::QSessionManager(QGuiApplication *app, QString &id, QString &key)
    : QObject(*(new QSessionManagerPrivate(id, key)), app)
{
}

QSessionManager::~QSessionManager()
{
}

/*!
    Returns the identifier of the current session.

    If the application has been restored from an earlier session, this
    identifier is the same as it was in the earlier session.

    \sa sessionKey(), QGuiApplication::sessionId()
*/
QString QSessionManager::sessionId() const
{
    Q_D(const QSessionManager);
    return d->platformSessionManager->sessionId();
}

/*!
    \fn QString QSessionManager::sessionKey() const

    Returns the session key in the current session.

    If the application has been restored from an earlier session, this key is
    the same as it was when the previous session ended.

    The session key changes with every call of commitData() or saveState().

    \sa sessionId(), QGuiApplication::sessionKey()
*/
QString QSessionManager::sessionKey() const
{
    Q_D(const QSessionManager);
    return d->platformSessionManager->sessionKey();
}


/*!
    Asks the session manager for permission to interact with the user. Returns
    true if interaction is permitted; otherwise returns \c false.

    The rationale behind this mechanism is to make it possible to synchronize
    user interaction during a shutdown. Advanced session managers may ask all
    applications simultaneously to commit their data, resulting in a much
    faster shutdown.

    When the interaction is completed we strongly recommend releasing the user
    interaction semaphore with a call to release(). This way, other
    applications may get the chance to interact with the user while your
    application is still busy saving data. (The semaphore is implicitly
    released when the application exits.)

    If the user decides to cancel the shutdown process during the interaction
    phase, you must tell the session manager that this has happened by calling
    cancel().

    Here's an example of how an application's QGuiApplication::commitDataRequest()
    might be implemented:

    \snippet code/src_gui_kernel_qguiapplication.cpp 1

    If an error occurred within the application while saving its data, you may
    want to try allowsErrorInteraction() instead.

    \sa QGuiApplication::commitDataRequest(), release(), cancel()
*/
bool QSessionManager::allowsInteraction()
{
    Q_D(QSessionManager);
    return d->platformSessionManager->allowsInteraction();
}

/*!
    Returns \c true if error interaction is permitted; otherwise returns \c false.

    This is similar to allowsInteraction(), but also enables the application to
    tell the user about any errors that occur. Session managers may give error
    interaction requests higher priority, which means that it is more likely
    that an error interaction is permitted. However, you are still not
    guaranteed that the session manager will allow interaction.

    \sa allowsInteraction(), release(), cancel()
*/
bool QSessionManager::allowsErrorInteraction()
{
    Q_D(QSessionManager);
    return d->platformSessionManager->allowsErrorInteraction();
}

/*!
    Releases the session manager's interaction semaphore after an interaction
    phase.

    \sa allowsInteraction(), allowsErrorInteraction()
*/
void QSessionManager::release()
{
    Q_D(QSessionManager);
    d->platformSessionManager->release();
}

/*!
    Tells the session manager to cancel the shutdown process.  Applications
    should not call this function without asking the user first.

    \sa allowsInteraction(), allowsErrorInteraction()
*/
void QSessionManager::cancel()
{
    Q_D(QSessionManager);
    d->platformSessionManager->cancel();
}

/*!
    Sets the application's restart hint to \a hint. On application startup, the
    hint is set to \c RestartIfRunning.

    \note These flags are only hints, a session manager may or may not respect
    them.

    We recommend setting the restart hint in QGuiApplication::saveStateRequest()
    because most session managers perform a checkpoint shortly after an
    application's
    startup.

    \sa restartHint()
*/
void QSessionManager::setRestartHint(QSessionManager::RestartHint hint)
{
    Q_D(QSessionManager);
    d->platformSessionManager->setRestartHint(hint);
}

/*!
    \fn QSessionManager::RestartHint QSessionManager::restartHint() const

    Returns the application's current restart hint. The default is
    \c RestartIfRunning.

    \sa setRestartHint()
*/
QSessionManager::RestartHint QSessionManager::restartHint() const
{
    Q_D(const QSessionManager);
    return d->platformSessionManager->restartHint();
}

/*!
    If the session manager is capable of restoring sessions it will execute
    \a command in order to restore the application. The command defaults to

    \snippet code/src_gui_kernel_qguiapplication.cpp 2

    The \c -session option is mandatory; otherwise QGuiApplication cannot
    tell whether it has been restored or what the current session identifier
    is.
    See QGuiApplication::isSessionRestored() and
    QGuiApplication::sessionId() for details.

    If your application is very simple, it may be possible to store the entire
    application state in additional command line options. This is usually a
    very bad idea because command lines are often limited to a few hundred
    bytes. Instead, use QSettings, temporary files, or a database for this
    purpose. By marking the data with the unique sessionId(), you will be able
    to restore the application in a future  session.

    \sa restartCommand(), setDiscardCommand(), setRestartHint()
*/
void QSessionManager::setRestartCommand(const QStringList &command)
{
    Q_D(QSessionManager);
    d->platformSessionManager->setRestartCommand(command);
}

/*!
    Returns the currently set restart command.

    To iterate over the list, you can use the \l foreach pseudo-keyword:

    \snippet code/src_gui_kernel_qguiapplication.cpp 3

    \sa setRestartCommand(), restartHint()
*/
QStringList QSessionManager::restartCommand() const
{
    Q_D(const QSessionManager);
    return d->platformSessionManager->restartCommand();
}

/*!
    Sets the discard command to the given \a command.

    \sa discardCommand(), setRestartCommand()
*/
void QSessionManager::setDiscardCommand(const QStringList &command)
{
    Q_D(QSessionManager);
    d->platformSessionManager->setDiscardCommand(command);
}

/*!
    Returns the currently set discard command.

    To iterate over the list, you can use the \l foreach pseudo-keyword:

    \snippet code/src_gui_kernel_qguiapplication.cpp 4

    \sa setDiscardCommand(), restartCommand(), setRestartCommand()
*/
QStringList QSessionManager::discardCommand() const
{
    Q_D(const QSessionManager);
    return d->platformSessionManager->discardCommand();
}

/*!
    \overload

    Low-level write access to the application's identification and state
    records are kept in the session manager.

    The property called \a name has its value set to the string \a value.
*/
void QSessionManager::setManagerProperty(const QString &name,
                                         const QString &value)
{
    Q_D(QSessionManager);
    d->platformSessionManager->setManagerProperty(name, value);
}

/*!
    Low-level write access to the application's identification and state record
    are kept in the session manager.

    The property called \a name has its value set to the string list \a value.
*/
void QSessionManager::setManagerProperty(const QString &name,
                                         const QStringList &value)
{
    Q_D(QSessionManager);
    d->platformSessionManager->setManagerProperty(name, value);
}

/*!
    Returns \c true if the session manager is currently performing a second
    session management phase; otherwise returns \c false.

    \sa requestPhase2()
*/
bool QSessionManager::isPhase2() const
{
    Q_D(const QSessionManager);
    return d->platformSessionManager->isPhase2();
}

/*!
    Requests a second session management phase for the application. The
    application may then return immediately from the
    QGuiApplication::commitDataRequest() or QApplication::saveStateRequest()
    function, and they will be called again once most or all other
    applications have finished their session management.

    The two phases are useful for applications such as the X11 window manager
    that need to store information about another application's windows and
    therefore have to wait until these applications have completed their
    respective session management tasks.

    \note If another application has requested a second phase it may get called
    before, simultaneously with, or after your application's second phase.

    \sa isPhase2()
*/
void QSessionManager::requestPhase2()
{
    Q_D(QSessionManager);
    d->platformSessionManager->requestPhase2();
}

QT_END_NAMESPACE

#endif // QT_NO_SESSIONMANAGER