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    {{Template:I18n/Language Navigation Bar|Development/Tutorials/Session Management}}
     


    {{TutorialBrowser|
    {{TutorialBrowser|


    series=TBD|
    series=Basics|


    name=Session Management|
    name=Session Management|


    pre=[[Development/Tutorials/pre|TBD]]|
    pre=[[Development/Tutorials/Creating_Libraries|Creating Libraries]]|


    next=[[Development/Tutorials/next|TBD]]|  
    next=|  


    reading=[http://doc.trolltech.com/4.4/session.html Session Management in the Qt documentation]; [http://api.kde.org/4.x-api/kdelibs-apidocs/kdeui/html/classKMainWindow.html KMainWindow]; [http://api.kde.org/4.x-api/kdelibs-apidocs/kdeui/html/classKApplication.html KApplication]
    reading=[http://doc.trolltech.com/4.4/session.html Session Management in the Qt documentation]; [http://api.kde.org/4.x-api/kdelibs-apidocs/kdeui/html/classKMainWindow.html KMainWindow]; [http://api.kde.org/4.x-api/kdelibs-apidocs/kdeui/html/classKApplication.html KApplication]
    Line 16: Line 16:
    ==About KDE and X11 session management==
    ==About KDE and X11 session management==


    Since KDE 1.0, the legacy X11R4 and ICCCM session management protocols
    Since KDE 1.0, KDE supports the legacy X11R4 and ICCCM session management protocols. It will restart with the specified command all legacy applications that define the <tt>WM_COMMAND</tt> property or support the <tt>WM_SAVE_YOURSELF</tt> protocol. It will also restore the window geometries on a best effort basis.
    are supported. Legacy applications that define the <tt>WM_COMMAND</tt>
    property or support the <tt>WM_SAVE_YOURSELF</tt> protocol will be restarted
    with the specified command.  The window geometries will be restored on a best
    effort basis.


    Since KDE 2.0, also the standard X11R6 session management protocol XSMP
    Since KDE 2.0, KDE also supports the standard X11R6 session management protocol XSMP and uses it. You can download the official documentation of the
    is supported and used. The official documentation of the
    standard from the X Consortium's FTP server  
    standard can be 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]. Unlike the legacy protocols, the new X11R6
    [http://stuff.mit.edu/afs/sipb/contrib/doc/X11/hardcopy/SM/xsmp.PS.gz ftp.x.org]. Unlike the legacy protocols, the new X11R6
    session management gives a chance to save application
    session management gives a chance to save application
    Line 32: Line 27:
    protocol is the support for a clean and safe logout procedure even if the
    protocol is the support for a clean and safe logout procedure even if the
    users decides not to restore the session next time. The protocol gives
    users decides not to restore the session next time. The protocol gives
    applications the possibility to interact with the user in case they are in
    applications the possibility to interact with the user if they are in
    danger to lose some data, and to cancel the shutdown process if necessary.
    danger to lose some data, and to cancel the shutdown process if necessary.


    ==Further Reading==
    ==Further Reading==


    An introductive overview of session management functionality and
    An introductory overview of session management functionality and
    the Qt API for it is available from [http://doc.trolltech.com/4.4/session.html doc.trolltech.com].
    the Qt API for it is available from [http://doc.trolltech.com/4.4/session.html doc.trolltech.com].


    Line 44: Line 39:
    hide all the ugly details from the programmer. Basically, a
    hide all the ugly details from the programmer. Basically, a
    [http://api.kde.org/4.x-api/kdelibs-apidocs/kdeui/html/classKApplication.html KApplication] manages a
    [http://api.kde.org/4.x-api/kdelibs-apidocs/kdeui/html/classKApplication.html KApplication] manages a
    [http://api.kde.org/4.x-api/kdelibs-apidocs/kdecore/html/classKConfig.html KConfig] configuration object (available trought
    [http://api.kde.org/4.x-api/kdelibs-apidocs/kdecore/html/classKConfig.html KConfig] configuration object (available trough
    [http://api.kde.org/4.x-api/kdelibs-apidocs/kdeui/html/classKApplication.html#8f88369c240d6d90a04d29b2761989d9 KApplication::sessionConfig()])
    [http://api.kde.org/4.x-api/kdelibs-apidocs/kdeui/html/classKApplication.html#8f88369c240d6d90a04d29b2761989d9 KApplication::sessionConfig()])
    for you, that your application can utilize to store session specific data.
    for you, that your application can use to store session specific data.


    Please read the respective class documentation, especially the one of
    Please read the class documentation, especially the one of
    [http://api.kde.org/4.x-api/kdelibs-apidocs/kdeui/html/classKMainWindow.html KMainWindow], for a detailed interface description. With the advanced
    [http://api.kde.org/4.x-api/kdelibs-apidocs/kdeui/html/classKMainWindow.html KMainWindow], for a detailed interface description. With the advanced
    functionality in [http://api.kde.org/4.x-api/kdelibs-apidocs/kdeui/html/classKMainWindow.html KMainWindow], it's really just a matter of a few lines to get even a multi-window application to retains its state between
    functionality in [http://api.kde.org/4.x-api/kdelibs-apidocs/kdeui/html/classKMainWindow.html KMainWindow], it's really just a matter of a few lines to get even a multi-window application to retains its state between
    Line 55: Line 50:
    ==Implementing session management in your application==
    ==Implementing session management in your application==


    Here's just a brief overview how things are done. Again, see the
    Here's just a brief overview how you can add session management to your application. Again, see the class documentation for details.
    respective class documentation for details.


    Implementing session management in KDE is easy. If your main window inherits from [http://api.kde.org/4.x-api/kdelibs-apidocs/kdeui/html/classKMainWindow.html KMainWindow], you have just 2 things to do:
    Implementing session management in KDE is easy. If your main window inherits from [http://api.kde.org/4.x-api/kdelibs-apidocs/kdeui/html/classKMainWindow.html KMainWindow], you have just 2 things to do:
    Line 65: Line 59:
    ===Reimplement some virtual functions of KMainWindow===
    ===Reimplement some virtual functions of KMainWindow===


    [http://api.kde.org/4.x-api/kdelibs-apidocs/kdeui/html/classKMainWindow.html KMainWindow] will save its position, geometry and positions of toolbars and menubar on logout.
    [http://api.kde.org/4.x-api/kdelibs-apidocs/kdeui/html/classKMainWindow.html KMainWindow] will automatically save its position, geometry and positions of toolbars and menu bar on logout - and restore it on the next startup.
    * To warn the user that the application or some windows have unsaved data on close or logout (for example: show a dialog with the buttons "Save changes" and "Discard changes"), reimplement [http://api.kde.org/4.x-api/kdelibs-apidocs/kdeui/html/classKMainWindow.html#f8c5708414be62f259114b0453ef8432 queryClose()].
     
    * To save additional data, reimplement [http://api.kde.org/4.x-api/kdelibs-apidocs/kdeui/html/classKMainWindow.html#4c7a6c395eec0bb245cd9ad6c884f897 saveProperties()]. (For a text editor, that would be the loaded files, for example.) Note that no user interaction is allowed in this function! For example, you may not display any dialog!
    For every other data that your application needs to restore a session, you have to write the code for saving and restoring yourself. However, [http://api.kde.org/4.x-api/kdelibs-apidocs/kdeui/html/classKMainWindow.html KMainWindow] makes this task easy. You can just re-implement the following functions:
    * To read the additional data again on next login, reimplement [http://api.kde.org/4.x-api/kdelibs-apidocs/kdeui/html/classKMainWindow.html#c8d0d64ed5b309ba1da410423120d0a6 readProperties()].
    * [http://api.kde.org/4.x-api/kdelibs-apidocs/kdeui/html/classKMainWindow.html#4c7a6c395eec0bb245cd9ad6c884f897 saveProperties()]: This function is called only when the session manager closes the application (and not when the user closes the application). To save the data that you need to restore the session, reimplement this function. (For a text editor that would be the list of loaded files) Note that you may not do any user interaction in this function! (For example, you may not display any dialog!)
    These functions are called automatically by [http://api.kde.org/4.x-api/kdelibs-apidocs/kdeui/html/classKMainWindow.html KMainWindow] respectively by the session manager. Note that it is not determined if [http://api.kde.org/4.x-api/kdelibs-apidocs/kdeui/html/classKMainWindow.html#4c7a6c395eec0bb245cd9ad6c884f897 saveProperties()] is called before or after [http://api.kde.org/4.x-api/kdelibs-apidocs/kdeui/html/classKMainWindow.html#f8c5708414be62f259114b0453ef8432 queryClose()]! Please read documentation of the respective functions before reimplementing them.
    * [http://api.kde.org/4.x-api/kdelibs-apidocs/kdeui/html/classKMainWindow.html#c8d0d64ed5b309ba1da410423120d0a6 readProperties()]: To read the data again on next login, reimplement this function.
     
    Furthermore, the function [http://api.kde.org/4.x-api/kdelibs-apidocs/kdeui/html/classKMainWindow.html#f8c5708414be62f259114b0453ef8432 queryClose()] could be interesting for you. This function is called ''always'' before the window is closed, either by the user or indirectly by the session manager. ''(Note that this is not the case for a call of KApplication::quit() because this function will exit the event loop without causing a close event for the main windows. It will even not destroy them.)'' Typically, here you can warn the user that the application or some windows have unsaved data on close or logout (example: show a dialog with the buttons "Save changes" and "Discard changes"). However, for session management it isn't nice to need a user interaction before closing, so you better avoid this. Note that it is not determined if [http://api.kde.org/4.x-api/kdelibs-apidocs/kdeui/html/classKMainWindow.html#4c7a6c395eec0bb245cd9ad6c884f897 saveProperties()] is called before or after [http://api.kde.org/4.x-api/kdelibs-apidocs/kdeui/html/classKMainWindow.html#f8c5708414be62f259114b0453ef8432 queryClose()]!


    To save your application-wide properties (data that is only needed once per application, and not for each main window) reimplement [http://api.kde.org/4.x-api/kdelibs-apidocs/kdeui/html/classKMainWindow.html#cf811d77a3acdcf2b61f8826429615a7 saveGlobalProperties()] and it's counterpart [http://api.kde.org/4.x-api/kdelibs-apidocs/kdeui/html/classKMainWindow.html#2d4da4f305f00e8a5c94f5b978334231 readGlobalProperties].  Normally, you don't need these functions.
    ''To save your application-wide properties (data that is only needed once per application, and not for each main window instance) reimplement [http://api.kde.org/4.x-api/kdelibs-apidocs/kdeui/html/classKMainWindow.html#cf811d77a3acdcf2b61f8826429615a7 saveGlobalProperties()] and it's counterpart [http://api.kde.org/4.x-api/kdelibs-apidocs/kdeui/html/classKMainWindow.html#2d4da4f305f00e8a5c94f5b978334231 readGlobalProperties].  Normally, you don't need these functions.''


    ===Add session management support to your main() function===
    ===Add session management support to your main() function===


    While [http://api.kde.org/4.x-api/kdelibs-apidocs/kdeui/html/classKMainWindow.html#4c7a6c395eec0bb245cd9ad6c884f897 KMainWindow::saveProperties()] and [http://api.kde.org/4.x-api/kdelibs-apidocs/kdeui/html/classKMainWindow.html#f8c5708414be62f259114b0453ef8432 KMainWindow::queryClose()] will be called automatically, [http://api.kde.org/4.x-api/kdelibs-apidocs/kdeui/html/classKMainWindow.html#c8d0d64ed5b309ba1da410423120d0a6 KMainWindow::readProperties()] will not. You have to add some code to your main() function to implement session restoring.
    While [http://api.kde.org/4.x-api/kdelibs-apidocs/kdeui/html/classKMainWindow.html#4c7a6c395eec0bb245cd9ad6c884f897 KMainWindow::saveProperties()] (and [http://api.kde.org/4.x-api/kdelibs-apidocs/kdeui/html/classKMainWindow.html#f8c5708414be62f259114b0453ef8432 KMainWindow::queryClose()]) will be called automatically, [http://api.kde.org/4.x-api/kdelibs-apidocs/kdeui/html/classKMainWindow.html#c8d0d64ed5b309ba1da410423120d0a6 KMainWindow::readProperties()] will not. You have to add some code to your main() function to add session restoring.


    Imagine you have an
    Imagine you have an
    Line 82: Line 78:
    [http://api.kde.org/4.x-api/kdelibs-apidocs/kdeui/html/classKXmlGuiWindow.html KXmlGuiWindow], which inherits from
    [http://api.kde.org/4.x-api/kdelibs-apidocs/kdeui/html/classKXmlGuiWindow.html KXmlGuiWindow], which inherits from
    [http://api.kde.org/4.x-api/kdelibs-apidocs/kdeui/html/classKMainWindow.html KMainWindow]). In your main() function, you would then create/restore the
    [http://api.kde.org/4.x-api/kdelibs-apidocs/kdeui/html/classKMainWindow.html KMainWindow]). In your main() function, you would then create/restore the
    application windows with something like:
    application windows with something like this:


    <code cppqt>
    <syntaxhighlight lang="cpp-qt">
    KApplication app;
    KApplication app;
    if ( app.isSessionRestored() ) {
    if ( app.isSessionRestored() ) {
    Line 90: Line 86:
    } else {
    } else {
       // create default application as usual
       // create default application as usual
       // for example:
       // example:
       MyWindow * window = new MyWindow();
       MyWindow * window = new MyWindow();
       // # will be replaced with numbers that are guaranteed
       // The function will replace '#' with numbers that are
       // to be unique in the application:
       // unique within the application:
       window->setObjectName("MyWindow#");
       window->setObjectName("MyWindow#");
       window->show();
       window->show();
    }
    }
    return app.exec();
    return app.exec();
    </code>
    </syntaxhighlight>


    [http://api.kde.org/4.x-api/kdelibs-apidocs/kdeui/html/kmainwindow_8h.html#88ce427e39f425eefa5a94d746eb2bed kRestoreMainWindows<>()] will create (on the heap) as many instances of your main windows as have existed in the last session and call [http://api.kde.org/4.x-api/kdelibs-apidocs/kdeui/html/classKMainWindow.html#46e01bd1aa6d488f1be2a5010030efb2 KMainWindow::restore()] with the correct arguments. Note that also QWidget::show() is called implicitly.
    [http://api.kde.org/4.x-api/kdelibs-apidocs/kdeui/html/kmainwindow_8h.html#88ce427e39f425eefa5a94d746eb2bed kRestoreMainWindows<>()] will create (on the heap) as many instances of your main windows as have existed in the last session and call [http://api.kde.org/4.x-api/kdelibs-apidocs/kdeui/html/classKMainWindow.html#46e01bd1aa6d488f1be2a5010030efb2 KMainWindow::restore()] with the correct arguments. Note that also QWidget::show() is called implicitly.
    Line 104: Line 100:
    About setObjectName("MyWindow#"): For session management and window management to work properly, all main windows in the application should have a different name. If you don't do it, KMainWindow will create a unique name, but it's recommended to explicitly pass a window name that will also describe the type of the window. If there can be several windows of the same type, append '#' (hash) to the name, and KMainWindow will replace it with numbers to make the names unique. For example, for a mail client which has one main window showing the mails and folders, and which can also have one or more windows for composing mails, the name for the folders window should be e.g. "mainwindow" and for the composer windows "composer#".
    About setObjectName("MyWindow#"): For session management and window management to work properly, all main windows in the application should have a different name. If you don't do it, KMainWindow will create a unique name, but it's recommended to explicitly pass a window name that will also describe the type of the window. If there can be several windows of the same type, append '#' (hash) to the name, and KMainWindow will replace it with numbers to make the names unique. For example, for a mail client which has one main window showing the mails and folders, and which can also have one or more windows for composing mails, the name for the folders window should be e.g. "mainwindow" and for the composer windows "composer#".


    With this you can easily restore all toplevel windows of your application.
    With this you can easily restore all top-level windows of your application.


    It is also possible to restore different types of toplevel windows (each
    It is also possible to restore different types of top-level windows (each
    derived from [http://api.kde.org/4.x-api/kdelibs-apidocs/kdeui/html/classKMainWindow.html KMainWindow], of course) within one application. Imagine you have three classes of main windows: childMW1, childMW2 and childMW3:
    derived from [http://api.kde.org/4.x-api/kdelibs-apidocs/kdeui/html/classKMainWindow.html KMainWindow], of course) within one application. Imagine you have three classes of main windows: childMW1, childMW2 and childMW3:


    <code cppqt>
    <syntaxhighlight lang="cpp-qt">
    KApplication app;
    KApplication app;
    if ( app.isSessionRestored() ) {
    if ( app.isSessionRestored() ) {
    Line 115: Line 111:
    } else {
    } else {
       // create default application as usual
       // create default application as usual
       // for example:
       // example:
       childMW1* window1 = new childMW1();
       childMW1* window1 = new childMW1();
       childMW2* window2 = new childMW2();
       childMW2* window2 = new childMW2();
       childMW3* window3 = new childMW3();
       childMW3* window3 = new childMW3();
       // # will be replaced with numbers that are guaranteed
       // The function will replace '#' with numbers that are
       // to be unique in the application:
       // unique within the application:
       window1->setObjectName("type1mainWindow#");
       window1->setObjectName("type1mainWindow#");
       window2->setObjectName("type2mainWindow#");
       window2->setObjectName("type2mainWindow#");
    Line 129: Line 125:
    }
    }
    return app.exec();
    return app.exec();
    </code>
    </syntaxhighlight>


    Currently, the [http://api.kde.org/4.x-api/kdelibs-apidocs/kdeui/html/kmainwindow_8h.html#88ce427e39f425eefa5a94d746eb2bed kRestoreMainWindows<>()] template functions are provided for up to three template arguments.
    Currently, kdelibs provides the [http://api.kde.org/4.x-api/kdelibs-apidocs/kdeui/html/kmainwindow_8h.html#88ce427e39f425eefa5a94d746eb2bed kRestoreMainWindows<>()] template functions for up to three template arguments.


    ==Appendix: Architecture of the KDE session manager==
    ==Appendix: Architecture of the KDE session manager==


    The session management server in KDE is called '''ksmserver''' and it is
    The name of the session management server in KDE is '''ksmserver''' and it is
    part of the '''kdebase''' package.  The server interacts with the KDE window
    part of the '''kdebase''' package.  The server interacts with the KDE window
    manager '''kwin''' to save and restore the window geometries and to perform
    manager '''kwin''' to save and restore the window geometries and to perform

    Revision as of 18:32, 15 July 2012


    Session Management
    Tutorial Series   Basics
    Previous   Creating Libraries
    What's Next  
    Further Reading   Session Management in the Qt documentation; KMainWindow; KApplication

    About KDE and X11 session management

    Since KDE 1.0, KDE supports the legacy X11R4 and ICCCM session management protocols. It will restart with the specified command all legacy applications that define the WM_COMMAND property or support the WM_SAVE_YOURSELF protocol. It will also restore the window geometries on a best effort basis.

    Since KDE 2.0, KDE also supports the standard X11R6 session management protocol XSMP and uses it. You can download the official documentation of the standard from the X Consortium's FTP server ftp.x.org. Unlike the legacy protocols, the new X11R6 session management gives a chance to save application dependent settings when you log out. A text editor, for instance, would save the names of the loaded files and would reload them when you log in again. Another major advantage of the new protocol is the support for a clean and safe logout procedure even if the users decides not to restore the session next time. The protocol gives applications the possibility to interact with the user if they are in danger to lose some data, and to cancel the shutdown process if necessary.

    Further Reading

    An introductory overview of session management functionality and the Qt API for it is available from doc.trolltech.com.

    In KDE, the classes KApplication and KMainWindow hide all the ugly details from the programmer. Basically, a KApplication manages a KConfig configuration object (available trough KApplication::sessionConfig()) for you, that your application can use to store session specific data.

    Please read the class documentation, especially the one of KMainWindow, for a detailed interface description. With the advanced functionality in KMainWindow, it's really just a matter of a few lines to get even a multi-window application to retains its state between different user sessions.

    Implementing session management in your application

    Here's just a brief overview how you can add session management to your application. Again, see the class documentation for details.

    Implementing session management in KDE is easy. If your main window inherits from KMainWindow, you have just 2 things to do:

    • Reimplement some virtual functions of KMainWindow.
    • Add session management support to your main() function.

    That's all.

    Reimplement some virtual functions of KMainWindow

    KMainWindow will automatically save its position, geometry and positions of toolbars and menu bar on logout - and restore it on the next startup.

    For every other data that your application needs to restore a session, you have to write the code for saving and restoring yourself. However, KMainWindow makes this task easy. You can just re-implement the following functions:

    • saveProperties(): This function is called only when the session manager closes the application (and not when the user closes the application). To save the data that you need to restore the session, reimplement this function. (For a text editor that would be the list of loaded files) Note that you may not do any user interaction in this function! (For example, you may not display any dialog!)
    • readProperties(): To read the data again on next login, reimplement this function.

    Furthermore, the function queryClose() could be interesting for you. This function is called always before the window is closed, either by the user or indirectly by the session manager. (Note that this is not the case for a call of KApplication::quit() because this function will exit the event loop without causing a close event for the main windows. It will even not destroy them.) Typically, here you can warn the user that the application or some windows have unsaved data on close or logout (example: show a dialog with the buttons "Save changes" and "Discard changes"). However, for session management it isn't nice to need a user interaction before closing, so you better avoid this. Note that it is not determined if saveProperties() is called before or after queryClose()!

    To save your application-wide properties (data that is only needed once per application, and not for each main window instance) reimplement saveGlobalProperties() and it's counterpart readGlobalProperties. Normally, you don't need these functions.

    Add session management support to your main() function

    While KMainWindow::saveProperties() (and KMainWindow::queryClose()) will be called automatically, KMainWindow::readProperties() will not. You have to add some code to your main() function to add session restoring.

    Imagine you have an application with a main window MyWindow inherited from KMainWindow (or from KXmlGuiWindow, which inherits from KMainWindow). In your main() function, you would then create/restore the application windows with something like this:

    KApplication app;
    if ( app.isSessionRestored() ) {
      kRestoreMainWindows< MyWindow >();
    } else {
      // create default application as usual
      // example:
      MyWindow * window = new MyWindow();
      // The function will replace '#' with numbers that are
      // unique within the application:
      window->setObjectName("MyWindow#");
      window->show();
    }
    return app.exec();
    

    kRestoreMainWindows<>() will create (on the heap) as many instances of your main windows as have existed in the last session and call KMainWindow::restore() with the correct arguments. Note that also QWidget::show() is called implicitly.

    About setObjectName("MyWindow#"): For session management and window management to work properly, all main windows in the application should have a different name. If you don't do it, KMainWindow will create a unique name, but it's recommended to explicitly pass a window name that will also describe the type of the window. If there can be several windows of the same type, append '#' (hash) to the name, and KMainWindow will replace it with numbers to make the names unique. For example, for a mail client which has one main window showing the mails and folders, and which can also have one or more windows for composing mails, the name for the folders window should be e.g. "mainwindow" and for the composer windows "composer#".

    With this you can easily restore all top-level windows of your application.

    It is also possible to restore different types of top-level windows (each derived from KMainWindow, of course) within one application. Imagine you have three classes of main windows: childMW1, childMW2 and childMW3:

    KApplication app;
    if ( app.isSessionRestored() ) {
      kRestoreMainWindows< childMW1, childMW2, childMW3 >();
    } else {
      // create default application as usual
      // example:
      childMW1* window1 = new childMW1();
      childMW2* window2 = new childMW2();
      childMW3* window3 = new childMW3();
      // The function will replace '#' with numbers that are
      // unique within the application:
      window1->setObjectName("type1mainWindow#");
      window2->setObjectName("type2mainWindow#");
      window3->setObjectName("type3mainWindow#");
      window1->show();
      window2->show();
      window3->show();
    }
    return app.exec();
    

    Currently, kdelibs provides the kRestoreMainWindows<>() template functions for up to three template arguments.

    Appendix: Architecture of the KDE session manager

    The name of the session management server in KDE is ksmserver and it is part of the kdebase package. The server interacts with the KDE window manager kwin to save and restore the window geometries and to perform legacy session management. To make session management work, ksmserver has to be started as last process of the X login procedure. This happens automatically at the end of the startkde script.


    Initial Author: Matthias Ettrich