QSessionManager(3qt)QSessionManager(3qt)NAMEQSessionManager - Access to the session manager
SYNOPSIS
#include <qsessionmanager.h>
Inherits QObject.
Public Members
QString sessionId () const
QString sessionKey () const
void * handle () const
bool allowsInteraction ()
bool allowsErrorInteraction ()
void release ()
void cancel ()
enum RestartHint { RestartIfRunning, RestartAnyway, RestartImmediately,
RestartNever }
void setRestartHint ( RestartHint hint )
RestartHint restartHint () const
void setRestartCommand ( const QStringList & command )
QStringList restartCommand () const
void setDiscardCommand ( const QStringList & )
QStringList discardCommand () const
void setManagerProperty ( const QString & name, const QString & value )
void setManagerProperty ( const QString & name, const QStringList &
value )
bool isPhase2 () const
void requestPhase2 ()
DESCRIPTION
The QSessionManager class provides access to the session manager.
The session manager is responsible for session management, most
importantly for interruption and resumption. A "session" is a kind of
record of the state of the system, e.g. which applications were run at
start up and which applications are currently running. 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.
Use QSettings to save and restore an individual application's settings,
e.g. window positions, recently used files, etc.
QSessionManager provides an interface between the application and the
session manager so that the program can work well with the session
manager. In Qt, session management requests for action are handled by
the two virtual functions QApplication::commitData() and
QApplication::saveState(). Both provide a reference to a session
manager object as argument, to allow the application to communicate
with the session manager.
During a session management action (i.e. within commitData() and
saveState()), no user interaction is possible unless the application
got explicit permission from the session manager. You ask for
permission by calling allowsInteraction() or, if it's really urgent,
allowsErrorInteraction(). Qt does not enforce this, but the session
manager may.
You can try to abort the shutdown process by calling cancel(). The
default commitData() function does this if some top-level window
rejected its closeEvent().
For sophisticated session managers provided on Unix/X11,
QSessionManager offers further possibilites to fine-tune an
application's session management behavior: setRestartCommand(),
setDiscardCommand(), setRestartHint(), setProperty(), requestPhase2().
See the respective function descriptions for further details.
See also Main Window and Related Classes and Environment Classes.
Member Type Documentation
QSessionManager::RestartHint
This enum type defines the circumstances under which this application
wants to be restarted by the session manager. The current values are
QSessionManager::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.
QSessionManager::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.)
QSessionManager::RestartImmediately - the application wants to be
started immediately whenever it is not running.
QSessionManager::RestartNever - the application does not want to be
restarted automatically.
The default hint is RestartIfRunning.
MEMBER FUNCTION DOCUMENTATIONbool QSessionManager::allowsErrorInteraction ()
This is similar to allowsInteraction(), but also tells the session
manager that an error occurred. Session managers may give error
interaction request 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.
See also allowsInteraction(), release(), and cancel().
bool QSessionManager::allowsInteraction ()
Asks the session manager for permission to interact with the user.
Returns TRUE if interaction is permitted; otherwise returns 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 QApplication::commitData()
might be implemented:
void MyApplication::commitData( QSessionManager& sm ) {
if ( sm.allowsInteraction() ) {
switch ( QMessageBox::warning(
yourMainWindow,
tr("Application Name"),
tr("Save changes to document Foo?"),
tr("&Yes"),
tr("&No"),
tr("Cancel"),
0, 2) ) {
case 0: // yes
sm.release();
// save document here; if saving fails, call sm.cancel()
break;
case 1: // continue without saving
break;
default: // cancel
sm.cancel();
break;
}
} else {
// we did not get permission to interact, then
// do something reasonable instead.
}
}
If an error occurred within the application while saving its data, you
may want to try allowsErrorInteraction() instead.
See also QApplication::commitData(), release(), and cancel().
void QSessionManager::cancel ()
Tells the session manager to cancel the shutdown process. Applications
should not call this function without first asking the user.
See also allowsInteraction() and allowsErrorInteraction().
QStringList QSessionManager::discardCommand () const
Returns the currently set discard command.
Note that if you want to iterate over the list, you should iterate over
a copy, e.g.
QStringList list = mySession.discardCommand();
QStringList::Iterator it = list.begin();
while( it != list.end() ) {
myProcessing( *it );
++it;
}
See also setDiscardCommand(), restartCommand(), and
setRestartCommand().
void * QSessionManager::handle () const
X11 only: returns a handle to the current SmcConnection.
bool QSessionManager::isPhase2 () const
Returns TRUE if the session manager is currently performing a second
session management phase; otherwise returns FALSE.
See also requestPhase2().
void QSessionManager::release ()
Releases the session manager's interaction semaphore after an
interaction phase.
See also allowsInteraction() and allowsErrorInteraction().
void QSessionManager::requestPhase2 ()
Requests a second session management phase for the application. The
application may then return immediately from the
QApplication::commitData() or QApplication::saveState() 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 that if another application has requested a second phase it may
get called before, simultaneously with, or after your application's
second phase.
See also isPhase2().
QStringList QSessionManager::restartCommand () const
Returns the currently set restart command.
Note that if you want to iterate over the list, you should iterate over
a copy, e.g.
QStringList list = mySession.restartCommand();
QStringList::Iterator it = list.begin();
while( it != list.end() ) {
myProcessing( *it );
++it;
}
See also setRestartCommand() and restartHint().
RestartHint QSessionManager::restartHint () const
Returns the application's current restart hint. The default is
RestartIfRunning.
See also setRestartHint().
QString QSessionManager::sessionId () const
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 that earlier session.
See also sessionKey() and QApplication::sessionId().
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().
See also sessionId() and QApplication::sessionKey().
void QSessionManager::setDiscardCommand ( const QStringList & )
See also discardCommand() and setRestartCommand().
void QSessionManager::setManagerProperty ( const QString & name, const
QStringList & value )
Low-level write access to the application's identification and state
record are kept in the session manager.
The property called name has its value set to the string list value.
void QSessionManager::setManagerProperty ( const QString & name, const QString
& value )
This is an overloaded member function, provided for convenience. It
behaves essentially like the above function.
Low-level write access to the application's identification and state
records are kept in the session manager.
The property called name has its value set to the string value.
void QSessionManager::setRestartCommand ( const QStringList & command )
If the session manager is capable of restoring sessions it will execute
command in order to restore the application. The command defaults to
appname -session id
The -session option is mandatory; otherwise QApplication cannot tell
whether it has been restored or what the current session identifier is.
See QApplication::isSessionRestored() and QApplication::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, or 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.
See also restartCommand(), setDiscardCommand(), and setRestartHint().
void QSessionManager::setRestartHint ( RestartHint hint )
Sets the application's restart hint to hint. On application startup the
hint is set to RestartIfRunning.
Note that these flags are only hints, a session manager may or may not
respect them.
We recommend setting the restart hint in QApplication::saveState()
because most session managers perform a checkpoint shortly after an
application's startup.
See also restartHint().
SEE ALSO
http://doc.trolltech.com/qsessionmanager.html
http://www.trolltech.com/faq/tech.html
COPYRIGHT
Copyright 1992-2007 Trolltech ASA, http://www.trolltech.com. See the
license file included in the distribution for a complete license
statement.
AUTHOR
Generated automatically from the source code.
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Trolltech AS 2 February 2007 QSessionManager(3qt)