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author | Timothy Pearson <kb9vqf@pearsoncomputing.net> | 2011-11-08 12:31:36 -0600 |
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committer | Timothy Pearson <kb9vqf@pearsoncomputing.net> | 2011-11-08 12:31:36 -0600 |
commit | d796c9dd933ab96ec83b9a634feedd5d32e1ba3f (patch) | |
tree | 6e3dcca4f77e20ec8966c666aac7c35bd4704053 /doc/session.doc | |
download | tqt3-d796c9dd933ab96ec83b9a634feedd5d32e1ba3f.tar.gz tqt3-d796c9dd933ab96ec83b9a634feedd5d32e1ba3f.zip |
Test conversion to TQt3 from Qt3 8c6fc1f8e35fd264dd01c582ca5e7549b32ab731
Diffstat (limited to 'doc/session.doc')
-rw-r--r-- | doc/session.doc | 177 |
1 files changed, 177 insertions, 0 deletions
diff --git a/doc/session.doc b/doc/session.doc new file mode 100644 index 000000000..51341d47f --- /dev/null +++ b/doc/session.doc @@ -0,0 +1,177 @@ +/**************************************************************************** +** +** Qt session management overview documentation +** +** Copyright (C) 1992-2008 Trolltech ASA. All rights reserved. +** +** This file is part of the Qt 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 Qt Foundation. +** +** Please review the following information to ensure GNU General +** Public Licensing retquirements 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 Qt + +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 + + +*/ |