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==Introduction==
 
==Introduction==
  
A KConfig Module is a small library with a @ref KCModule subclass containing
+
This howto describes how to write KConfig Modules (KCMs from now on). These KCM
code which builds and support a interface for configuration tasks. The module
+
can appear in System Settings or in the configuration dialog of individual applications.
is then encapsulated in a parent application, for example kcmshell, System
+
Settings or a KCMultiDialog.
+
  
This HOWTO describes how to write KConfig Modules(KCMs from now on). This
+
A KCM is made of two elements:
technology was originally designed for KControl. Although KControl is the
+
* A shared library
application where the KCM tehnology is the most used, it is used in several
+
* A desktop file
other places as well, such as Kopete and Kontact. This HOWTO describes how to
+
write config modules, regardless of where it will be used. KConfig Modules
+
were originally called KControl Modules.
+
  
==Implementing==
+
==The shared library==
  
 
Implementing a KCM is done by:
 
Implementing a KCM is done by:
# Subclassing the @ref KCModule class. In this documentation we assume the class inheriting from KCModule is named FooKcm.
+
# Subclassing the {{class|KCModule}} class. In this documentation we assume the class inheriting from KCModule is named FooKcm.
# Exporting the module so that systemsettings or kcmshell can find it.
+
# Exporting the module so that System Settings or kcmshell4 can find it.
  
The prefered way to export the module is through KPluginFactory. Here is how to
+
The prefered way to export the module is through {{class|KPluginFactory}}. Here is how to
 
do it:
 
do it:
  
Line 26: Line 36:
  
 
     K_PLUGIN_FACTORY(FooKcmFactory, registerPlugin<FooKcm>();)
 
     K_PLUGIN_FACTORY(FooKcmFactory, registerPlugin<FooKcm>();)
     K_EXPORT_PLUGIN(FooKcmFactory("kcm_foo", "kcm_foo"))
+
     K_EXPORT_PLUGIN(FooKcmFactory("kcm_foo" /* kcm name */, "kcm_foo" /* catalog name */))
 
</syntaxhighlight>
 
</syntaxhighlight>
  
If you get errors, make sure that the constructor of your derived class equals
+
If you get errors, make sure the constructor signature of your derived class matches
the one of the KCModule baseclass (the QStringList argument matters).
+
with the signature of {{class|KCModule}} constructor (the QVariantList argument matters).
  
If you need to export more than one module per library, you have to use the
+
If the name of your module is "foo", the name of the library should be
old loader. That is, you need to create a function like this:
+
"kcm_foo.so". It should be installed into $KDEDIR/lib/kde4.
 +
 
 +
===Exporting more than one module===
 +
 
 +
If you need to export more than one module per library, you have to declare them another way: you must create C functions named "create_${kcm_name}".  For
 +
example if your module exposes two KCMs named Foo1 and Foo2, the
 +
"create_" functions would look like this:
  
 
<syntaxhighlight lang="cpp">
 
<syntaxhighlight lang="cpp">
 
     extern "C"
 
     extern "C"
 
     {
 
     {
      KCModule *create_foo(QWidget *parent, const char *name)
+
        KCModule *create_foo1(QWidget *parent, const char *name)
      {
+
        {
         return new FooKcm(parent, name);
+
            return new Foo1Kcm(parent, name);
      };
+
         };
 +
        KCModule *create_foo2(QWidget *parent, const char *name)
 +
        {
 +
            return new Foo2Kcm(parent, name);
 +
        };
 
     }
 
     }
 
</syntaxhighlight>
 
</syntaxhighlight>
  
This function and the implementation of the module is then compiled as a
+
Additionally, you will need to add "X-KDE-FactoryName" keys to your
shared library. If the name of your modules is 'foo', the name of the library
+
desktop file. (see below)
should be kcm_foo.so and should be installed into $KDEDIR/lib/kde4 (see @ref kcm_install).
+
 
 +
===Initializing on startup===
  
==Initializing on startup==
+
It is possible to get code from the KCM to be run at startup by kcminit.
  
If your module needs to initialize on KDE session startup, you must have a
+
To do so you must declare a function named "kcminit_${module}", like this:
construct like:
+
  
 
<syntaxhighlight lang="cpp">
 
<syntaxhighlight lang="cpp">
 
     extern "C"
 
     extern "C"
 
     {
 
     {
      KCModule *init_foo(QWidget *parent, const char *name)
+
        KDEEXPORT void kcminit_foo()
      {
+
        {
        // Do initialization here
+
            // Do initialization here
      };
+
        };
 
     }
 
     }
 
</syntaxhighlight>
 
</syntaxhighlight>
  
Don't forget to add X-KDE-Init to your desktop file. (see below)
+
You must also add a "X-KDE-Init-Symbol" key to your desktop file. (see below)
  
 
==The desktop file==
 
==The desktop file==
  
To declare a KCModule's existence a desktop file must be installed in the proper place (see @ref kcm_install).
+
To declare a KCModule's existence a desktop file must be installed in the proper place.
  
It could be a good idea to have a look at the [http://www.freedesktop.org/Standards/desktop-entry-spec desktop file specification].
+
Desktop files are defined in the [http://www.freedesktop.org/Standards/desktop-entry-spec desktop file specification].
  
A KCM's .desktop file supports the following .desktop directives:
+
===Mandatory keys===
  
;X-KDE-Library
+
A KCM desktop file ''must'' contains the following keys:
This is the name of the library, without the kcm_ prefix. So in the example,
+
the library name would be "foo".
+
  
;X-KDE-FactoryName
+
;Type
This entry can be used to set the name of the factory function in the library.
+
Should be "Service".
If you only have one KCModule in a library this directive is not needed. If
+
you have several KCMs in one library you will need a .desktop file for each
+
KCM.
+
  
For example, if you have a library named: kcm_frog.so with two modules, named "kermit" and "quak", you would have:
+
;X-KDE-ServiceTypes
 +
Should be "KCModule" for most KCM. If you want to use the kcminit feature it should be "KCModule,KCModuleInit".
  
<syntaxhighlight lang="ini">
+
;Icon
X-KDE-Library=frog
+
Specifies the icon for the module.
X-KDE-FactoryName=kermit
+
</syntaxhighlight>
+
  
in one of the .desktop files, and in the other:
+
;Exec
 +
Should be "kcmshell4 foo".
  
<syntaxhighlight lang="ini">
+
;Name
X-KDE-Library=frog
+
This will be used by System Settings as your KCM label.
X-KDE-FactoryName=quak
+
</syntaxhighlight>
+
  
The module loader would then call the "create_kermit" and "create_quak" functions respectively.
+
;Comment
 +
This text shows up in the title area in System Settings. If the module is not
 +
grouped with other modules it will also be used as a tooltip in the KCM list
 +
view.
  
;X-KDE-RootOnly
+
;Categories
If this is set to "true", the module must be executed with root permissions.
+
Should contain at least "Qt;KDE;X-KDE-settings-system;".
The module loader will then show the module in greyed-out (disabled) state
+
with a warning until the "modify" button is pressed which allows running the
+
module in an root environment using kdesu and QXEmbed.
+
  
 
;X-KDE-ParentApp
 
;X-KDE-ParentApp
The application you put in this entry determines in what situations it will
+
Set this to "kcontrol" if you want your KCM to show up in System Settings.
show. For example, if the line says "X-KDE-ParentApp=kcontrol" the module will
+
show up in KControl. It is very crucial the selected ParentApp is correct,
+
otherwise the KCM will show up in unnecessary places.
+
  
;X-KDE-Init
+
The application you put in this key determines in what situations your KCM will
If the module has to perform some action at system startup, use this entry to
+
show. It is crucial to select a correct ParentApp, otherwise the KCM will show up in unnecessary places.
build the name of a function to call. if X-KDE-Init is "bell", for example,
+
the function "init_bell" is called in the library indicated by X-KDE-Library.
+
  
;X-KDE-Test-Module
+
;X-KDE-System-Settings-Parent-Category
If the module has to perform some action at system startup, use this entry to
+
Defines where the KCM will appear in System Settings.
build the name of a function to call. if X-KDE-Init is "bell", for example,
+
the function "init_bell" is called in the library indicated by X-KDE-Library.
+
  
;NoDisplay
+
Possible values at the time of this writing are:
If this is set to true the module will not show up in kcontrol or when viewed
+
* settings-lost-and-found
with kcmshell. This is usable when you need to do something at startup(X-KDE-
+
* settings-hardware
Init etc.) but don't want the module to show up in kcontrol, eg. the module
+
* settings-network-and-connectivity
has no GUI.
+
* settings-system-administration
 +
* settings-application-appearance-and-behavior
 +
* settings-workspace-appearance-and-behavior
  
;Name
+
You can get a list of possible categories with this command, which lists all toplevel categories:
This is 'labels' for the KCMs and fill the nodes in the three view. Please see
+
the KCM Guidelines on how to pick a good Name.
+
  
;Comment
+
<pre>
This directive shows up in the main area in KControl if you select a top node
+
ktraderclient --servicetype SystemSettingsCategory --constraint "[X-KDE-System-Settings-Parent-Category] == ''" | grep DesktopEntryName
in the three view. See the same section as for Name in the KCM Guidelines for
+
</pre>
how to pick a good phrase.
+
  
;Categories
+
Just do not use the "settings-lost-and-found" entry.
This describes where the KCM should be put in KControl's navigation. It should
+
look like "Categories=QT;KDE;X;" where X is the category. A list of available
+
categories, as well as which one to choose is found in the KCM Guidelines.
+
  
;Icon
+
;X-KDE-Keywords
Specifies the icon for the module.
+
A comma-separated list containing words the search functionality should trigger
 +
on.
  
;Exec
+
;X-KDE-Library
Should say "Exec=kcmshell4 modulename".
+
This is the name of the library, without the "kcm_" prefix. In our example,
 +
it should be "foo".
  
;Type
+
===Optional keys===
Should say "Type=Application".
+
Additionally the KCM desktop file ''may'' contains the following keys:
  
;Keywords
+
;X-KDE-FactoryName
A semi colon separated list containing words/phrases search functionality
+
This entry can be used to set the name of the factory function in the library.  If you only have one KCModule in a library this key is not needed. If you have several KCMs in one library you will need a desktop file for each KCM.
should trigger on.
+
  
To summarize, a valid KCM .desktop file ''must'' contain these directives:
+
For example, if you have a library named: kcm_frog.so with two modules, named "kermit" and "quak", kcm_kermit.desktop would contain:
 +
 
 +
<syntaxhighlight lang="ini">
 +
X-KDE-Library=frog
 +
X-KDE-FactoryName=kermit
 +
</syntaxhighlight>
 +
 
 +
and "kcm_quak.desktop" would contain:
 +
 
 +
<syntaxhighlight lang="ini">
 +
X-KDE-Library=frog
 +
X-KDE-FactoryName=quak
 +
</syntaxhighlight>
 +
 
 +
The module loader would then call the "create_kermit" and "create_quak" functions respectively.
 +
 
 +
;X-KDE-Init-Symbol
 +
If the module has to perform some action at system startup, use this entry to build the name of a function to call. if X-KDE-Init-Symbol is "bell", for example, the function "kcminit_bell" is called in the library indicated by X-KDE-Library.
 +
 
 +
;NoDisplay
 +
If this is set to true the module will not show up in System Settings or when viewed with kcmshell4. This is useful when you need to do something at startup using X-KDE-Init but don't want the module to show up in System Settings.
  
* Name
+
You can also make the value of this key depend on the output of a program, using the "[$e]" key suffix. For example:
* Icon
+
* Type=Application
+
* Exec=kcmshell modulename
+
* Categories=Qt;KDE;X; (replace X with your category)
+
* Keywords
+
* X-KDE-Library
+
* X-KDE-ParentApp
+
* Comment
+
  
Additionally, a KCM .desktop file ''may'' contain:
+
<pre>
 +
Hidden[$e]=$(if test -e /dev/js*; then echo "false"; else echo "true"; fi)
 +
</pre>
  
* X-KDE-Init
+
This example executes the given code in a shell and uses the stdout output for the Hidden value (so it's either Hidden=true or Hidden=false).
* X-KDE-Test-Module
+
* NoDisplay
+
* X-KDE-Root-Only
+
* X-KDE-Factory-Name
+
* DocPath
+
  
Any other directives (except translations) can safely be removed, since they
+
==Example CMakeLists.txt==
most likely are abundant or are left over's from old KDE versions. For example,
+
X-ModuleType was relevant for KDE 2.0 but not in any new versions.
+
  
==Defining a CMakeLists.txt for the KCM==
+
Here is a minimal CMakeLists.txt which builds and installs the shared library and the
 +
desktop files at the right places:
  
 
<syntaxhighlight lang="cmake">
 
<syntaxhighlight lang="cmake">
Line 188: Line 199:
 
include(MacroLibrary)
 
include(MacroLibrary)
  
set(FOO_KCM_SRCS
+
set(FOO_SRCS
     foo_kcm.cpp
+
     foo.cpp
 
     # Other sources go there
 
     # Other sources go there
 
)
 
)
  
kde4_add_plugin(kcm_foo ${FOO_KCM_SRCS})
+
kde4_add_plugin(kcm_foo ${FOO_SRCS})
  
 
target_link_libraries(kcm_foo
 
target_link_libraries(kcm_foo
Line 215: Line 226:
 
===kcmshell4===
 
===kcmshell4===
  
Consider you want to run a module standalone. Call "kcmshell4 module". For
+
You can run one or several modules independently with "kcmshell4 [module_name]". For example, to get the font and the desktop color settings, use "kcmshell4 fonts colors".
example, to get the font and the desktop color settings, use:
+
  
kcmshell4 fonts colors
+
To get a list of the available modules, use "kcmshell4 --list".
  
 
===KCMultiDialog===
 
===KCMultiDialog===
Line 225: Line 235:
 
are two ways to accomplish this:
 
are two ways to accomplish this:
  
First option is to use {{class|KCMultiDialog}}. This is a simple dialog that
+
The first option is to simply fork and call "kcmshell4 foo".
can show an abitrary number of modules in a normal {{class|KDialogBase}}. The
+
 
advantage is that you can control the behaviour and the results much easier
+
The second option is to use {{class|KCMultiDialog}}. This is a simple dialog
that with a separate process. And as your module is a simple library, you can
+
which can show an arbitrary number of modules in a normal {{class|KDialog}}.
just link to it anyway.
+
This approach gives you finer control than starting kcmshell4 in a separate process.
  
Second option is to call "kcmshell4 modules".
+
Since your module is a simple library, you can just link to it anyway.
  
 
===KCModuleContainer===
 
===KCModuleContainer===
  
The class {{class|KCModuleContainer}} allows great flexibility with handling modules.
+
The class {{class|KCModuleContainer}} allows great flexibility to handle modules.
 
The API docs explains its usage the best.
 
The API docs explains its usage the best.
  
===Debugging your module===
+
==Debugging your module==
  
 
You can attach gdb, valgrind or whatever to "kcmshell4 [yourmodule]" to track
 
You can attach gdb, valgrind or whatever to "kcmshell4 [yourmodule]" to track
down leaks or crashes. If you need to trace it down inside systemsettings, make sure
+
down leaks or crashes. If you need to trace it down inside System Settings, make sure
you pass --nofork to systemsettings on startup.
+
you pass --nofork to System Settings on startup.
  
 
You really want to use kcmshell4 for debugging as long as your debugging does
 
You really want to use kcmshell4 for debugging as long as your debugging does
not involve debugging bad interaction with the systemsettings framework itself.
+
not involve debugging bad interaction with the System Settings framework itself.
  
 
----
 
----
Line 251: Line 261:
 
== About this howto ==
 
== About this howto ==
  
This howto has been imported from http://websvn.kde.org/trunk/www/sites/developer/documentation/other/kcm_howto.html?view=markup and updated to KDE4 by Aurélien Gâteau.
+
This howto has been imported from http://websvn.kde.org/trunk/www/sites/developer/documentation/other/kcm_howto.html?view=markup and refreshed for KDE4 by Aurélien Gâteau <agateau@kde.org>.
  
 
Original copyright header:
 
Original copyright header:

Revision as of 18:46, 19 July 2012


KCM HowTo
Tutorial Series   Plugins and KParts
Previous  
What's Next  
Further Reading   KCModule Class Reference

Contents

Introduction

This howto describes how to write KConfig Modules (KCMs from now on). These KCM can appear in System Settings or in the configuration dialog of individual applications.

A KCM is made of two elements:

  • A shared library
  • A desktop file

The shared library

Implementing a KCM is done by:

  1. Subclassing the KCModule class. In this documentation we assume the class inheriting from KCModule is named FooKcm.
  2. Exporting the module so that System Settings or kcmshell4 can find it.

The prefered way to export the module is through KPluginFactory. Here is how to do it:

    #include <KPluginFactory>
 
    K_PLUGIN_FACTORY(FooKcmFactory, registerPlugin<FooKcm>();)
    K_EXPORT_PLUGIN(FooKcmFactory("kcm_foo" /* kcm name */, "kcm_foo" /* catalog name */))

If you get errors, make sure the constructor signature of your derived class matches with the signature of KCModule constructor (the QVariantList argument matters).

If the name of your module is "foo", the name of the library should be "kcm_foo.so". It should be installed into $KDEDIR/lib/kde4.

Exporting more than one module

If you need to export more than one module per library, you have to declare them another way: you must create C functions named "create_${kcm_name}". For example if your module exposes two KCMs named Foo1 and Foo2, the "create_" functions would look like this:

    extern "C"
    {
        KCModule *create_foo1(QWidget *parent, const char *name)
        {
            return new Foo1Kcm(parent, name);
        };
        KCModule *create_foo2(QWidget *parent, const char *name)
        {
            return new Foo2Kcm(parent, name);
        };
    }

Additionally, you will need to add "X-KDE-FactoryName" keys to your desktop file. (see below)

Initializing on startup

It is possible to get code from the KCM to be run at startup by kcminit.

To do so you must declare a function named "kcminit_${module}", like this:

    extern "C"
    {
        KDEEXPORT void kcminit_foo()
        {
            // Do initialization here
        };
    }

You must also add a "X-KDE-Init-Symbol" key to your desktop file. (see below)

The desktop file

To declare a KCModule's existence a desktop file must be installed in the proper place.

Desktop files are defined in the desktop file specification.

Mandatory keys

A KCM desktop file must contains the following keys:

Type

Should be "Service".

X-KDE-ServiceTypes

Should be "KCModule" for most KCM. If you want to use the kcminit feature it should be "KCModule,KCModuleInit".

Icon

Specifies the icon for the module.

Exec

Should be "kcmshell4 foo".

Name

This will be used by System Settings as your KCM label.

Comment

This text shows up in the title area in System Settings. If the module is not grouped with other modules it will also be used as a tooltip in the KCM list view.

Categories

Should contain at least "Qt;KDE;X-KDE-settings-system;".

X-KDE-ParentApp

Set this to "kcontrol" if you want your KCM to show up in System Settings.

The application you put in this key determines in what situations your KCM will show. It is crucial to select a correct ParentApp, otherwise the KCM will show up in unnecessary places.

X-KDE-System-Settings-Parent-Category

Defines where the KCM will appear in System Settings.

Possible values at the time of this writing are:

  • settings-lost-and-found
  • settings-hardware
  • settings-network-and-connectivity
  • settings-system-administration
  • settings-application-appearance-and-behavior
  • settings-workspace-appearance-and-behavior

You can get a list of possible categories with this command, which lists all toplevel categories:

ktraderclient --servicetype SystemSettingsCategory --constraint "[X-KDE-System-Settings-Parent-Category] == ''" | grep DesktopEntryName

Just do not use the "settings-lost-and-found" entry.

X-KDE-Keywords

A comma-separated list containing words the search functionality should trigger on.

X-KDE-Library

This is the name of the library, without the "kcm_" prefix. In our example, it should be "foo".

Optional keys

Additionally the KCM desktop file may contains the following keys:

X-KDE-FactoryName

This entry can be used to set the name of the factory function in the library. If you only have one KCModule in a library this key is not needed. If you have several KCMs in one library you will need a desktop file for each KCM.

For example, if you have a library named: kcm_frog.so with two modules, named "kermit" and "quak", kcm_kermit.desktop would contain:

X-KDE-Library=frog
X-KDE-FactoryName=kermit

and "kcm_quak.desktop" would contain:

X-KDE-Library=frog
X-KDE-FactoryName=quak

The module loader would then call the "create_kermit" and "create_quak" functions respectively.

X-KDE-Init-Symbol

If the module has to perform some action at system startup, use this entry to build the name of a function to call. if X-KDE-Init-Symbol is "bell", for example, the function "kcminit_bell" is called in the library indicated by X-KDE-Library.

NoDisplay

If this is set to true the module will not show up in System Settings or when viewed with kcmshell4. This is useful when you need to do something at startup using X-KDE-Init but don't want the module to show up in System Settings.

You can also make the value of this key depend on the output of a program, using the "[$e]" key suffix. For example:

Hidden[$e]=$(if test -e /dev/js*; then echo "false"; else echo "true"; fi)

This example executes the given code in a shell and uses the stdout output for the Hidden value (so it's either Hidden=true or Hidden=false).

Example CMakeLists.txt

Here is a minimal CMakeLists.txt which builds and installs the shared library and the desktop files at the right places:

find_package(KDE4 REQUIRED)
 
include(KDE4Defaults)
include(MacroLibrary)
 
set(FOO_SRCS
    foo.cpp
    # Other sources go there
)
 
kde4_add_plugin(kcm_foo ${FOO_SRCS})
 
target_link_libraries(kcm_foo
    ${KDE4_KDEUI_LIBS}
    # Other necessary libraries go there
)
 
install(TARGETS kcm_foo
    DESTINATION ${PLUGIN_INSTALL_DIR}
)
 
install(FILES kcm_foo.desktop
    DESTINATION ${SERVICES_INSTALL_DIR}
)

What else do I need?

There are a number of additional things for convenience.

kcmshell4

You can run one or several modules independently with "kcmshell4 [module_name]". For example, to get the font and the desktop color settings, use "kcmshell4 fonts colors".

To get a list of the available modules, use "kcmshell4 --list".

KCMultiDialog

Sometimes, you may want to reuse your KCModule inside an application. There are two ways to accomplish this:

The first option is to simply fork and call "kcmshell4 foo".

The second option is to use KCMultiDialog. This is a simple dialog which can show an arbitrary number of modules in a normal KDialog. This approach gives you finer control than starting kcmshell4 in a separate process.

Since your module is a simple library, you can just link to it anyway.

KCModuleContainer

The class KCModuleContainer allows great flexibility to handle modules. The API docs explains its usage the best.

Debugging your module

You can attach gdb, valgrind or whatever to "kcmshell4 [yourmodule]" to track down leaks or crashes. If you need to trace it down inside System Settings, make sure you pass --nofork to System Settings on startup.

You really want to use kcmshell4 for debugging as long as your debugging does not involve debugging bad interaction with the System Settings framework itself.


About this howto

This howto has been imported from http://websvn.kde.org/trunk/www/sites/developer/documentation/other/kcm_howto.html?view=markup and refreshed for KDE4 by Aurélien Gâteau <agateau@kde.org>.

Original copyright header:

Copyright (C) 2003 Daniel Molkentin <molketin@kde.org>
Copyright (C) 2004 Frans Englich <frans.englich@telia.com>

Permission is granted to copy, distribute and/or modify this document under the
terms of the GNU Free Documentation License, Version 1.2 or any later version
published by the Free Software Foundation; with no Invariant Sections, no
Front-Cover Texts, and no Back-Cover Texts. A copy of the license is included
in the section entitled "GNU Free Documentation License".

KDE® and the K Desktop Environment® logo are registered trademarks of KDE e.V.Legal