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 xsm and is part of a standard X11R6 installation. As always with X11, a useful and informative manual page is provided. Using xsm is straightforward (apart from the clumsy Athena-based user interface). Here's a simple approach:

• Run X11R6.
• Create a dot file .xsmstartup in your home directory which contains the single line

  xterm
  

  This tells xsm that the default/failsafe session is just an xterm and nothing else. Otherwise xsm would try to invoke lots of clients including the windowmanager twm, which isn't very helpful.
• Now launch 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 SESSION_MANAGER environment variable points to the session manager you just started.
• Launch your application from the new xterm window. It will connect itself automatically to the session manager. You can check with the ClientList push button whether the connect was successful.
  Note: Never keep the ClientList open when you start or end session managed clients! Otherwise xsm is likely to crash.
• Use the session manager's Checkpoint and Shutdown buttons with different settings and see how your application behaves. The save type local means that the clients should save their state. It corresponds to the QApplication::saveState() function. The global save type asks applications to save their unsaved changes in permanent, globally accessible storage. It invokes QApplication::commitData().
• Whenever something crashes, blame xsm and not Qt. 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.