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diff --git a/doc/html/session.html b/doc/html/session.html new file mode 100644 index 0000000..1c0f5eb --- /dev/null +++ b/doc/html/session.html @@ -0,0 +1,152 @@ +<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN"> +<!-- /home/espenr/tmp/qt-3.3.8-espenr-2499/qt-x11-free-3.3.8/doc/session.doc:36 --> +<html> +<head> +<meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1"> +<title>Session Management</title> +<style type="text/css"><!-- +fn { margin-left: 1cm; text-indent: -1cm; } +a:link { color: #004faf; text-decoration: none } +a:visited { color: #672967; text-decoration: none } +body { background: #ffffff; color: black; } +--></style> +</head> +<body> + +<table border="0" cellpadding="0" cellspacing="0" width="100%"> +<tr bgcolor="#E5E5E5"> +<td valign=center> + <a href="index.html"> +<font color="#004faf">Home</font></a> + | <a href="classes.html"> +<font color="#004faf">All Classes</font></a> + | <a href="mainclasses.html"> +<font color="#004faf">Main Classes</font></a> + | <a href="annotated.html"> +<font color="#004faf">Annotated</font></a> + | <a href="groups.html"> +<font color="#004faf">Grouped Classes</font></a> + | <a href="functions.html"> +<font color="#004faf">Functions</font></a> +</td> +<td align="right" valign="center"><img src="logo32.png" align="right" width="64" height="32" border="0"></td></tr></table><h1 align=center>Session Management</h1> + + + +<p> <h2> Definitions +</h2> +<a name="1"></a><p> A <em>session</em> is a group of running applications, each of which has a +particular state. The session is controlled by a service called the <em>session</em> <em>manager</em>. The applications participating in the session are +called <em>session</em> <em>clients</em>. +<p> 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 <em>session</em> <em>management</em>. +<p> 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. +<p> <h2> Shutting a session down +</h2> +<a name="2"></a><p> 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! +<p> <h2> Protocols and support on different platforms +</h2> +<a name="3"></a><p> 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 <a href="qapplication.html#commitData">QApplication::commitData</a>() method. +<p> X11 has supported complete session management since X11R6. +<p> <h2> Getting session management to work with Qt +</h2> +<a name="4"></a><p> Start by reimplementing <a href="qapplication.html#commitData">QApplication::commitData</a>() 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: +<p> <center><img src="session.png" alt="A typical dialog on shutdown"></center> +<p> Example code to this dialog can be found in the documentation of <a href="qsessionmanager.html#allowsInteraction">QSessionManager::allowsInteraction</a>(). +<p> 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 <a href="qapplication.html#saveState">QApplication::saveState</a>(). All state data you are saving in this +function, should be marked with the session identifier <a href="qapplication.html#sessionId">QApplication::sessionId</a>(). This application specific identifier is +globally unique, so no clashes will occur. (See <a href="qsessionmanager.html">QSessionManager</a> for +information on saving/restoring the state of a particular Qt +application.) +<p> Restoration is usually done in the application's main() +function. Check if <a href="qapplication.html#isSessionRestored">QApplication::isSessionRestored</a>() is <tt>TRUE</tt>. If +that's the case, use the session identifier <a href="qapplication.html#sessionId">QApplication::sessionId</a>() again to access your state data and restore +the state of the application. +<p> <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 <a href="qobject.html#setName">QObject::setName</a>()). When +restoring the application, you must ensure that all restored +top level widgets are given the same unique names they had before. +<p> <h2> Testing and debugging session management +</h2> +<a name="5"></a><p> 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. +<p> 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 <tt>xsm</tt> and is part of a standard X11R6 +installation. As always with X11, a useful and informative manual page +is provided. Using <tt>xsm</tt> is straightforward (apart from the clumsy +Athena-based user interface). Here's a simple approach: +<p> <ul> +<li> Run X11R6. +<li> Create a dot file <tt>.xsmstartup</tt> in your home directory which +contains the single line +<pre> +xterm +</pre> + +This tells <tt>xsm</tt> that the default/failsafe session is just an xterm +and nothing else. Otherwise <tt>xsm</tt> would try to invoke lots of +clients including the windowmanager <tt>twm</tt>, which isn't very helpful. +<li> Now launch <tt>xsm</tt> 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 <tt>SESSION_MANAGER</tt> +environment variable points to the session manager you just started. +<li> Launch your application from the new xterm window. It will connect +itself automatically to the session manager. You can check with the <em>ClientList</em> push button whether the connect was successful.<br> +<strong>Note:</strong> Never keep the <em>ClientList</em> open when you +start or end session managed clients! Otherwise <tt>xsm</tt> is likely to +crash. +<li> Use the session manager's <em>Checkpoint</em> and <em>Shutdown</em> buttons +with different settings and see how your application behaves. The save +type <em>local</em> means that the clients should save their state. It +corresponds to the <a href="qapplication.html#saveState">QApplication::saveState</a>() function. The <em>global</em> save type asks applications to save their unsaved changes in +permanent, globally accessible storage. It invokes <a href="qapplication.html#commitData">QApplication::commitData</a>(). +<li> Whenever something crashes, blame <tt>xsm</tt> and not Qt. <tt>xsm</tt> 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. +</ul> +<p> +<!-- eof --> +<p><address><hr><div align=center> +<table width=100% cellspacing=0 border=0><tr> +<td>Copyright © 2007 +<a href="troll.html">Trolltech</a><td align=center><a href="trademarks.html">Trademarks</a> +<td align=right><div align=right>Qt 3.3.8</div> +</table></div></address></body> +</html> |