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| '''KDE Architecture - Session Management'''
| | This tutorial was updated and moved to https://develop.kde.org/docs/configuration/introduction/ |
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| KDE, since version 2.0, supports and uses the standard X11R6 session management
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| protocol XSMP. The official documentation of the standard can be
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| download from the X Consortium's FTP server [http://stuff.mit.edu/afs/sipb/contrib/doc/X11/hardcopy/SM/xsmp.PS.gz ftp.x.org].
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| KDE also supports the legacy X11R4 and ICCCM session
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| management protocols. Legacy applications that define the <tt>WM_COMMAND</tt>
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| property or support the <tt>WM_SAVE_YOURSELF</tt> protocol will be restarted
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| with the specified command. The window geometries will be restored on a best
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| effort basis.
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| Unlike these legacy protocols, the new X11R6 session management gives a
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| chance to save application dependent settings when you log out. A text
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| editor, for instance, would save the names of the loaded files and would
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| reload them when you log in again. Another major advantage of the new
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| protocol is the support for a clean and safe logout procedure even if the
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| users decides not to restore the session next time. The protocol gives
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| applications the possibility to interact with the user in case they are in
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| danger to lose some data, and to cancel the shutdown process if necessary.
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| An introductive overview of session management functionality and
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| the Qt API for it is available from [http://doc.trolltech.com/3.3/session.html doc.trolltech.com].
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| In KDE, the classes [http://api.kde.org/3.5-api/kdelibs-apidocs/kdecore/html/classKApplication.html KApplication]
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| and [http://api.kde.org/3.5-api/kdelibs-apidocs/kdeui/html/classKMainWindow.html KMainWindow]
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| hide all the ugly details from the programmer. Basically, a
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| KApplication manages a KConfig configuration object sessionConfig()
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| for you, that your application can utilize to store session specific data.
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| Please read the respective class documentation, especially the one of
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| KMainWindow, for a detailed interface description. With the advanced
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| functionality in KMainWindow, it's really just a matter of a few lines
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| to get even a multi-window application to retains its state between
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| different user sessions.
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| Here's just a brief overview how things are done. Again, see the
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| respective class documentation for details. Imagine you have an
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| application with a main window MyWindow inherited from KMainWindow. In
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| your main() function, you would then create/restore the application
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| windows with something like:
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| <code cppqt3>
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| if (kapp->isRestored()) {
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| RESTORE(MyWindow)
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| } else {
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| // create default application as usual
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| }
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| </code>
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| and reimplement the store/restore handlers in MyWindow to save and
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| restore all additional settings. For a text editor, that would be the
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| loaded files, for example:
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| <code cppqt3>
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| void MyWindow::saveProperties( KConfig* ) {
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| // save properties here
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| }
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| void MyWindow::readProperties( KConfig* ) {
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| // read properties here
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| }
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| </code>
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| Note that standard settings like window sizes, toolbar settings
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| etc. are automatically handled by the system.
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| With KMainWindow::classNameOfToplevel(), it is also possible to
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| restore different types of toplevel windows within one application. In
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| that case, the RESTORE macro is too primitive, use something like this
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| in your main() function instead:
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| <code cppqt3>
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| if (kapp->isRestored()){
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| int n = 1;
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| while (KMainWindow::canBeRestored(n)) {
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| if ( KMainWindow::classNameOfToplevel(n) == "MyWindow1" )
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| (new MyWindow1)->restore(n);
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| else if ( KMainWindow::classNameOfToplevel(n) == "MyWindow2" )
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| (new MyWindow2)->restore(n);
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| // and so on....
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| n++;
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| }
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| } else {
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| // create default application as usual
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| }
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| </code>
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| The session management server in KDE is called '''ksmserver''' and it is
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| part of the '''kdebase''' package. The server interacts with the KDE window
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| manager '''kwin''' to save and restore the window geometries and to perform
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| legacy session management. To make session management work, '''ksmserver'''
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| has to be started as last process of the X login procedure. This happens
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| automatically at the end of the '''startkde''' script.
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| [[Category:Programming]]
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| [[Category:Tutorial]]
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| [[Category:FAQs]] | |
