source: trunk/doc/src/session.qdoc@ 477

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41
42/*!
43 \page session.html
44 \title Session Management
45 \ingroup gui-programming
46
47 A \e session is a group of running applications, each of which has a
48 particular state. The session is controlled by a service called the \e
49 session \e manager. The applications participating in the session are
50 called \e{session clients}.
51
52 The session manager issues commands to its clients on behalf of the
53 user. These commands may cause clients to commit unsaved changes (for
54 example by saving open files), to preserve their state for future
55 sessions, or to terminate gracefully. The set of these operations is
56 called \e session \e management.
57
58 In the common case, a session consists of all applications that a
59 user runs on their desktop at a time. Under Unix/X11, however, a
60 session may include applications running on different computers and
61 may span multiple displays.
62
63 \section1 Shutting a Session Down
64
65 A session is shut down by the session manager, usually on behalf of
66 the user when they want to log out. A system might also perform an
67 automatic shutdown in an emergency situation, for example, if power is
68 about to be lost. Clearly there is a significant difference between
69 these types of shutdown. During the first, the user may want to
70 interact with the application, specifying exactly which files should
71 be saved and which should be discarded. In the latter case, there's no
72 time for interaction. There may not even be a user sitting in front of
73 the machine!
74
75
76 \section1 Protocols and Support on Different Platforms
77
78 On Mac OS X, and Microsoft Windows versions prior to Windows 2000,
79 there is nothing like complete session management for applications
80 yet, i.e. no restoring of previous sessions. (Windows 2000 and XP
81 provide "hibernation" where the entire memory is saved to disk and
82 restored when the machine is restarted.) They do support graceful
83 logouts where applications have the opportunity to cancel the process
84 after getting confirmation from the user. This is the functionality
85 that corresponds to the QApplication::commitData() method.
86
87 X11 has supported complete session management since X11R6.
88
89 \section1 Getting Session Management to Work with Qt