You can not select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
178 lines
8.0 KiB
178 lines
8.0 KiB
/****************************************************************************
|
|
**
|
|
** TQt session management overview documentation
|
|
**
|
|
** Copyright (C) 1992-2008 Trolltech ASA. All rights reserved.
|
|
**
|
|
** This file is part of the TQt GUI Toolkit.
|
|
**
|
|
** This file may be used under the terms of the GNU General
|
|
** Public License versions 2.0 or 3.0 as published by the Free
|
|
** Software Foundation and appearing in the files LICENSE.GPL2
|
|
** and LICENSE.GPL3 included in the packaging of this file.
|
|
** Alternatively you may (at your option) use any later version
|
|
** of the GNU General Public License if such license has been
|
|
** publicly approved by Trolltech ASA (or its successors, if any)
|
|
** and the KDE Free TQt Foundation.
|
|
**
|
|
** Please review the following information to ensure GNU General
|
|
** Public Licensing requirements will be met:
|
|
** http://trolltech.com/products/qt/licenses/licensing/opensource/.
|
|
** If you are unsure which license is appropriate for your use, please
|
|
** review the following information:
|
|
** http://trolltech.com/products/qt/licenses/licensing/licensingoverview
|
|
** or contact the sales department at sales@trolltech.com.
|
|
**
|
|
** This file may be used under the terms of the Q Public License as
|
|
** defined by Trolltech ASA and appearing in the file LICENSE.QPL
|
|
** included in the packaging of this file. Licensees holding valid Qt
|
|
** Commercial licenses may use this file in accordance with the Qt
|
|
** Commercial License Agreement provided with the Software.
|
|
**
|
|
** This file is provided "AS IS" with NO WARRANTY OF ANY KIND,
|
|
** INCLUDING THE WARRANTIES OF DESIGN, MERCHANTABILITY AND FITNESS FOR
|
|
** A PARTICULAR PURPOSE. Trolltech reserves all rights not granted
|
|
** herein.
|
|
**
|
|
**********************************************************************/
|
|
|
|
/*!
|
|
\page session.html
|
|
|
|
\title Session Management
|
|
|
|
\section1 Definitions
|
|
|
|
A \e session is a group of running applications, each of which has a
|
|
particular state. The session is controlled by a service called the \e
|
|
session \e manager. The applications participating in the session are
|
|
called \e session \e clients.
|
|
|
|
The session manager issues commands to its clients on behalf of the
|
|
user. These commands may cause clients to commit unsaved changes (for
|
|
example by saving open files), to preserve their state for future
|
|
sessions, or to terminate gracefully. The set of these operations is
|
|
called \e session \e management.
|
|
|
|
In the common case, a session consists of all applications that a
|
|
user runs on their desktop at a time. Under Unix/X11, however, a
|
|
session may include applications running on different computers and
|
|
may span multiple displays.
|
|
|
|
\section1 Shutting a session down
|
|
|
|
A session is shut down by the session manager, usually on behalf of
|
|
the user when they want to log out. A system might also perform an
|
|
automatic shutdown in an emergency situation, for example, if power is
|
|
about to be lost. Clearly there is a significant difference between
|
|
these types of shutdown. During the first, the user may want to
|
|
interact with the application, specifying exactly which files should
|
|
be saved and which should be discarded. In the latter case, there's no
|
|
time for interaction. There may not even be a user sitting in front of
|
|
the machine!
|
|
|
|
|
|
\section1 Protocols and support on different platforms
|
|
|
|
On Mac OS X and MS-Windows, there is nothing like complete session
|
|
management for applications yet, i.e. no restoring of previous
|
|
sessions. They do support graceful logouts where applications
|
|
have the opportunity to cancel the process after getting confirmation
|
|
from the user. This is the functionality that corresponds to the \l
|
|
QApplication::commitData() method.
|
|
|
|
X11 has supported complete session management since X11R6.
|
|
|
|
\section1 Getting session management to work with TQt
|
|
|
|
Start by reimplementing \l QApplication::commitData() to
|
|
enable your application to take part in the graceful logout process. If
|
|
you are only targeting the MS-Windows platform, this is all you can
|
|
and must provide. Ideally, your application should provide a shutdown
|
|
dialog similar to the following:
|
|
|
|
\img session.png A typical dialog on shutdown
|
|
|
|
Example code to this dialog can be found in the documentation of \l
|
|
QSessionManager::allowsInteraction().
|
|
|
|
For complete session management (only supported on X11R6 at present),
|
|
you must also take care of saving the application's state, and
|
|
potentially of restoring the state in the next life cycle of the
|
|
session. This saving is done by reimplementing \l
|
|
QApplication::saveState(). All state data you are saving in this
|
|
function, should be marked with the session identifier \l
|
|
QApplication::sessionId(). This application specific identifier is
|
|
globally unique, so no clashes will occur. (See \l QSessionManager for
|
|
information on saving/restoring the state of a particular Qt
|
|
application.)
|
|
|
|
Restoration is usually done in the application's main()
|
|
function. Check if \l QApplication::isSessionRestored() is \c TRUE. If
|
|
that's the case, use the session identifier \l
|
|
QApplication::sessionId() again to access your state data and restore
|
|
the state of the application.
|
|
|
|
<strong>Important:</strong> In order to allow the window manager to
|
|
restore window attributes such as stacking order or geometry
|
|
information, you must identify your top level widgets with
|
|
unique application-wide object names (see \l{QObject::setName()}). When
|
|
restoring the application, you must ensure that all restored
|
|
top level widgets are given the same unique names they had before.
|
|
|
|
\section1 Testing and debugging session management
|
|
|
|
Session management support on Mac OS X and Windows is fairly limited
|
|
due to the lack of this functionality in the operating system
|
|
itself. Simply shut the session down and verify that your application
|
|
behaves as expected. It may be useful to launch another application,
|
|
usually the integrated development environment, before starting your
|
|
application. This other application will get the shutdown message
|
|
afterwards, thus permitting you to cancel the shutdown. Otherwise you
|
|
would have to log in again after each test run, which is not a problem
|
|
per se, but is time consuming.
|
|
|
|
On Unix you can either use a desktop environment that supports
|
|
standard X11R6 session management or, the recommended method, use the
|
|
session manager reference implementation provided by the X Consortium.
|
|
This sample manager is called \c xsm and is part of a standard X11R6
|
|
installation. As always with X11, a useful and informative manual page
|
|
is provided. Using \c xsm is straightforward (apart from the clumsy
|
|
Athena-based user interface). Here's a simple approach:
|
|
|
|
\list
|
|
\i Run X11R6.
|
|
\i Create a dot file \c .xsmstartup in your home directory which
|
|
contains the single line
|
|
\code
|
|
xterm
|
|
\endcode
|
|
This tells \c xsm that the default/failsafe session is just an xterm
|
|
and nothing else. Otherwise \c xsm would try to invoke lots of
|
|
clients including the windowmanager \c twm, which isn't very helpful.
|
|
\i Now launch \c xsm from another terminal window. Both a session
|
|
manager window and the xterm will appear. The xterm has a nice
|
|
property that sets it apart from all the other shells you are
|
|
currently running: within its shell, the \c SESSION_MANAGER
|
|
environment variable points to the session manager you just started.
|
|
\i Launch your application from the new xterm window. It will connect
|
|
itself automatically to the session manager. You can check with the \e
|
|
ClientList push button whether the connect was successful.<br>
|
|
<strong>Note:</strong> Never keep the \e ClientList open when you
|
|
start or end session managed clients! Otherwise \c xsm is likely to
|
|
crash.
|
|
\i Use the session manager's \e Checkpoint and \e Shutdown buttons
|
|
with different settings and see how your application behaves. The save
|
|
type \e local means that the clients should save their state. It
|
|
corresponds to the \l QApplication::saveState() function. The \e
|
|
global save type asks applications to save their unsaved changes in
|
|
permanent, globally accessible storage. It invokes \l
|
|
QApplication::commitData().
|
|
\i Whenever something crashes, blame \c xsm and not Qt. \c xsm is far
|
|
from being a usable session manager on a user's desktop. It is,
|
|
however, stable and useful enough to serve as testing environment.
|
|
\endlist
|
|
|
|
|
|
*/
|