kdelibs/kdecore/kconfig_compiler/README.dox

/**
\page kconfig_compiler The KDE Configuration Compiler

kconfig_compiler generates C++ source code from an XML file containing 
information about configuration options (.kcfg) and a file that provides 
the code generation options (.kcfgc) The generated class is based on 
KConfigSkeleton and provides an API for the application to access its
configuration data.

The generated C++ source code is output to a .h and a .cpp file, whose base
name is the same as that of the .kcfgc file.

<h2>XML description of the configuration options</h2>

The structure of the .kcfg file is described by its DTD kcfg.xsd.

The \<kcfgfile\> tag may contain either the "name" attribute, which should be the name
of the configuration file described, or the "arg" attribute, which, if set to
"true", will allow you to pass the KSharedConfig::Ptr object to use.

If neither "name" nor "arg" is set, the default configuration file
("\<appname\>rc") will be used.

The \<include\> tags are optional and may contain C++ header files that
are needed to compile the code needed to compute default values. To generate
a \#include "..." statement instead of \#include \<...\>, enclose the header
file name in double quotes (e.g. \<include\>"header.h"\</include\>).

The remaining entries in the XML file are grouped by the tag \<group\> 
which describes the corresponding group in the configuration file.

The individual entries must have at least a name or a key. The key is used
as the key in the config file, while the name is used to create accessor and
modifier functions. If \<key\> is given, but not \<name\>, the name is
constructed by removing all spaces from \<key\>. If \<name\> is given, but
not \<key\>, the key is the same as \<name\>.

An entry must also have a type. The list of allowable types is
specified in the DTD and loosely follows the list of types supported
by the QVariant with exception of the clearly binary types
(e.g. Pixmap, Image...) which are not supported. Besides those basic
types the following special types are supported:

- Path  This is a string that is specially treated as a file-path. 
  In particular paths in the home directory are prefixed with $HOME in
  when being stored in the configuration file.
  
- Enum  This indicates an enumeration. The possible enum values and optional
  enum name should be provided via the \<choices\> tag. Enum values are
  accessed as integers by the application but stored as strings in the
  configuration file. This makes it possible to add more values at a later
  date without breaking compatibility.

- IntList  This indicates a list of integers. This information is provided
  to the application as QValueList<int>. Useful for storing QSplitter
  geometries.

An entry can optionally have a default value which is used as default when
the value isn't specified in any config file. Default values are interpreted
as literal constant values. If a default value needs to be computed
or if it needs to be obtained from a function call, the \<default\> tag
should contain the code="true" attribute. The contents of the \<default\>
tag is then considered to be a C++ expression. Note that in this case you
might have to add an \<include\> tag as described above, or a
SourceIncludeFiles entry in the .kcfgc file as described below, so that the
code which computes the default value can be compiled.

Additional code for computing default values can be provided outside any
entry definition via the \<code\> tag. The contents of the \<code\> tag is
inserted as-is. A typical use for this is to compute a common default value
which can then be referenced by multiple entries that follow.

<h2>Code generation options</h2>

The options for generating the C++ sources are read from the file with the
extension .kcfgc. To generate a class add the corresponding kcfgc file to the
SOURCES line in the Makefile.am.

The following options are read from the kcfgc file:

<table>
<tr>
  <td><b><i>Name</i></b></td>
  <td><b><i>Type</i></b></td>
  <td><b><i>Default</i></b></td>
  <td><b><i>Description</i></b></td>
</tr>
<tr>
  <td><b>File</b></td>
  <td>string</td>
  <td>programname.kcfg</td>
  <td>Name of kcfg file containing the options the class is generated for</td>
</tr>
<tr>
  <td><b>NameSpace</b></td>
  <td>string</td>
  <td>-</td>
  <td>Optional namespace for generated class</td>
</tr>
<tr>
  <td><b>ClassName</b></td>
  <td>string</td>
  <td>-</td>
  <td>Name of generated class (required)</td>
</tr>
<tr>
  <td><b>Inherits</b></td>
  <td>string</td>
  <td>KConfigSkeleton</td>
  <td>Class the generated class inherits from. This class must inherit
  KConfigSkeleton.</td>
</tr>
<tr>
  <td><b>Visibility</b></td>
  <td>string</td>
  <td>-</td>
  <td>Inserts visibility directive (for example KDE_EXPORT) between "class" keyword and class 
  name in header file</td>
</tr>
<tr>
  <td><b>Singleton</b></td>
  <td>bool</td>
  <td>false</td>
  <td>Generated class is a singleton.</td>
</tr>
<tr>
  <td><b>CustomAdditions</b></td>
  <td>bool</td>
  <td>-</td>
  <td></td>
</tr>
<tr>
  <td><b>MemberVariables</b></td>
  <td>string: public|protected|private|dpointer</td>
  <td>private</td>
  <td>C++ access modifier used for member variables holding the configuration
  values</td>
</tr>
<tr>
  <td><b>IncludeFiles</b></td>
  <td>comma separated list of strings</td>
  <td>-</td>
  <td>Names of files to be included in the header of the generated class. Enclose a
  file name in (escaped) double quotes to generate \#include "..." instead of
  \#include \<...\>.</td>
</tr>
<tr>
  <td><b>SourceIncludeFiles</b></td>
  <td>comma separated list of strings</td>
  <td>-</td>
  <td>Names of files to be included in the source file of the generated class. Enclose
  a file name in (escaped) double quotes to generate \#include "..." instead of
  \#include \<...\>.</td>
</tr>
<tr>
  <td><b>Mutators</b></td>
  <td>true, false or a comma separated list of options</td>
  <td>false</td>
  <td>If true, mutator functions for all configuration options are generated.
      If false, no mutator functions are generated. If a list is provided,
      mutator functions are generated for the options that are listed.</td> 
</tr>
<tr>
  <td><b>DefaultValueGetters</b></td>
  <td>true, false or a comma separated list of options</td>
  <td>false</td>
  <td>If true, functions to return the default value of all configuration options
      are generated. If false, no default value functions are generated. If a list
      is provided, default value functions are generated for the options that are listed.</td> 
</tr>
<tr>
  <td><b>ItemAccessors</b></td>
  <td>bool</td>
  <td>false</td>
  <td>Generate accessor functions for the KConfigSkeletonItem objects
  corresponding to the configuration options. If <b>SetUserTexts</b> is set,
  <b>ItemAccessors</b> also has to be set.</td>
</tr>
<tr>
  <td><b>SetUserTexts</b></td>
  <td>bool</td>
  <td>false</td>
  <td>Set the label and whatthis texts of the items from the kcfg file.If
  <b>SetUserTexts</b> is set, <b>ItemAccessors</b> also has to be set.</td>
</tr>
<tr>
  <td><b>GlobalEnums</b></td>
  <td>bool</td>
  <td>false</td>
  <td>If set to true all choices of Enum items will be created in the global
  scope of the generated class. If set to false, each Enum item whose enum is not
  explicitly named will get its own namespace for its choices.</td>
</tr>
<tr>
  <td><b>UseEnumTypes</b></td>
  <td>bool</td>
  <td>false</td>
  <td>If set to true, all Enum items whose enums are named will use enum types for
  the return value of accessor functions and for the parameter of mutator
  functions. This eliminates the need to cast accessor return values to the enum
  type if you want to use the enum type in your own code. If set to false,
  accessor return values and mutator parameters will be of type int.</td>
</tr>
<tr>
  <td><b>ForceStringFilename</b></td>
  <td>bool</td>
  <td>false</td>
  <td>If set to true, forces the first parameter of the generated class to be a QString when using an argument for the filename. This is useful to specify at runtime the filename of the configuration class.</td>
</table>


<h2>Advanced options</h2>

There are several possibilities to parameterize entries.

- Parameterized entries

An entry can be parameterized using a fixed range parameter specified with
the \<parameter\> tag. Such parameter can either be an Enum or an int. An Enum
parameter should specify the possible enumeration values with the \<choices\>
tag. An int parameter should specify its maximum value. Its minimum value
is always 0.

A parameterized entry is expanded to a number of entries, one for each
value in the parameter range. The name and key should contain a reference
to the parameter in the form of $(parameter-name). When expanding the entries
the $(parameter-name) part is replaced with the value of the parameter.
In the case of an Enum parameter it is replaced with the name of the
enumuration value. In the case of an int parameter it is replaced with
the numeric value of the parameter.

Parameterized entries all share the same default value unless different
default values have been specified for specific parameter values.
This can be done with the param= attribute of the \<default\>. When a
param attribute is specified the default value only applies to that
particular parameter value.

Example 1:
\verbatim
  <entry name="Color$(ColorIndex)" type="Color" key="color_$(ColorIndex)">
    <parameter name="ColorIndex" type="Int" max="3"/>
    <default param="0">#ff0000</default>
    <default param="1">#00ff00</default>
    <default param="2">#0000ff</default>
    <default param="3">#ffff00</default>
  </entry>
\endverbatim

The above describes 4 color configuration entries with the following defaults:

\verbatim
color_0=#ff0000
color_1=#00ff00
color_2=#0000ff
color_3=#ffff00
\endverbatim

The configuration options will be accessible to the application via
a QColor color(int ColorIndex) and a 
void setColor(int ColorIndex, const QColor &v) function.

Example 2:
\verbatim
  <entry name="Sound$(SoundEvent)" type="String" key="sound_$(SoundEvent)">
    <parameter name="SoundEvent" type="Enum">
      <values>
        <value>Explosion</value>
        <value>Crash</value>
        <value>Missile</value>
      </values>
    </parameter>
    <default param="Explosion">boom.wav</default>
    <default param="Crash">crash.wav</default>
    <default param="Missile">missile.wav</default>
  </entry>
\endverbatim

The above describes 3 string configuration entries with the following defaults:

sound_Explosion=boom.wav
sound_Crash=crash.wav
sound_Missile=missile.wav

The configuration options will be accessible to the application via
a QString sound(int SoundEvent) and a 
void setSound(int SoundEvent, const QString &v) function.

- Parameterized groups

A group name can be parametrized using a parameter given to the KConfigSkeleton
instance (which means this feature cannot be used with singleton classes).

Example 1:
\verbatim
  <kcfgfile name="testrc">
    <parameter name="groupname"/>
  </kcfgfile>
  <group name="$(groupname)">
    <entry key="Text" type="string">
    </entry>
  </group>
\endverbatim

In this case passing "Group2" as the 'groupname' parameter to the generated class
will make it use group "Group2" for the entry "Text".

- Enums

By default, if <b>GlobalEnums</b> is set to false, a separate named enum will be generated
for each Enum entry. Since each enum is defined in a little enclosing class of its own,
this allows the same Enum value names to be used in different enums. For example, the
.kcfg entry

\verbatim
<entry name="KeepData" type="Enum">
  <choices>
    <choice name="Do">
    <choice name="Dont">
  </choices>
</entry>
\endverbatim

will generate this public class containing the enum definition, inside the generated class:

\verbatim
    class EnumKeepData
    {
      public:
      enum type { Do, Dont, COUNT };
    };
\endverbatim

Alternatively, if <b>GlobalEnums</b> is set to true, all Enum items are defined as
unnamed enums in the global scope of the generated class. In this case, all Enum values
must have different names to avoid clashes. However, you can use a 'prefix' argument
in \<choices\> to prevent duplicate enum member names clashing. Using this, the Enum value
names are prefixed in code with the string you specify. For example, if <b>GlobalEnums</b>
is set to true, the .kcfg entry

\verbatim
<entry name="KeepData" type="Enum">
  <choices prefix="Keep_">
    <choice name="Do">
    <choice name="Dont">
  </choices>
</entry>
\endverbatim

will generate config file entries of "KeepData=Do" and "KeepData=Dont", but the enum
will be declared

\verbatim
    enum { Keep_Do, Keep_Dont };
\endverbatim

It is possible to specify your own name for a generated enum, by including a
'name' parameter in \<choices\>. Just like unnamed enums, this enum will be defined in
the global scope of the generated class (without any enclosing class of its own).
Therefore the names of Enum values must be unique across both unnamed enums (if
<b>GlobalEnums</b> is set to true) and all specifically named enums.

An example of a specifically named enum:

\verbatim
<entry name="KeepData" type="Enum">
  <choices name="Types">
    <choice name="Do">
    <choice name="Dont">
  </choices>
</entry>
\endverbatim

which results in the following enum declaration, inside the generated class:

\verbatim
    enum Types { Do, Dont };
\endverbatim

It is also possible to specify the use of enums external to the generated class, by
including the string "::" in the enum name - just ensure that it is sufficiently
qualified to be unambiguous in use. To specify use of an unnamed enum, append a
trailing "::". For example, to use the enum 'myEnum' defined in class ClassA, use
either of

\verbatim
<choices name="ClassA::myEnum">
<choices name="::ClassA::myEnum">
\endverbatim

To specify an unnamed enum in namespace ProgSpace, use

\verbatim
<choices name="ProgSpace::">
\endverbatim

To specify a top-level unnamed enum, use

\verbatim
<choices name="::">
\endverbatim

To specify the top-level enum 'anotherEnum', use

\verbatim
<choices name="::anotherEnum">
\endverbatim


- Signal support.

An entry can emit a signal when it gets changed. First of all, you must
define a list of signals for the configuration class. The signal's name may be
any legal identifier you wish. The \<argument\> tag allows you to specify arguments
for the emitted signal. It supports all types as defined in
the KConfigXT DTD. The argument value must specify the name, without spaces, of one
of the entries defined in the .kcfg file.
A signal definition can also contain a \<label\> tag which will be
the documentation line in the generated file.

\verbatim
<signal name="emoticonSettingsChanged" />

<signal name="styleChanged">
  <label>Tell when a complete style change.</label>
    <argument type="String">stylePath</argument>
    <argument type="String">StyleCSSVariant</argument>
</signal>
\endverbatim

After defining the signals, you must tell which signal to emit for the entry.
A signal can be emitted by multiple entries. Also, you don't need to specify the arguments
for a signal, the signal name will suffice.

\verbatim
<entry key="stylePath" type="String">
  <label>Absolute path to a directory containing a Adium/Kopete chat window style.</label>
  <emit signal="styleChanged" />
</entry>
\endverbatim

You can also use the generic configChanged() signal from KConfigSkeleton to notify your application
about configuration changes.

If you have questions or comments please contact Cornelius Schumacher
<schumacher@kde.org> or Waldo Bastian <bastian@kde.org>
*/