xmlns:its="http://www.w3.org/2005/11/its"

      xmlns:xi="http://www.w3.org/2003/XInclude"

      type="topic"

      id="documentation">

  <info>

    <link type="guide" xref="index#general-guidelines"/>

    <credit type="author copyright">

      <name>Federico Mena-Quintero</name>

      <email its:translate="no">federico@gnome.org</email>

      <years>2013</years>

    </credit>

    <credit type="author copyright">

      <name>Philip Withnall</name>

      <email its:translate="no">philip.withnall@collabora.co.uk</email>

      <years>2015</years>

    </credit>

    <credit type="author copyright">

      <name>The GTK+ Team</name>

    </credit>

    <include href="cc-by-sa-3-0.xml" xmlns="http://www.w3.org/2001/XInclude"/>

    <desc>Adding documentation to libraries and APIs</desc>

  </info>

  <title>Documentation</title>

  <synopsis>

    <title>Summary</title>

    <list>

      <item>

        Use gtk-doc with up-to-date settings for API documentation.

        (<link xref="#gtk-doc"/>)

      
</item>

      <item>

        Use XML entities for including external symbols into the documentation.

        (<link xref="#build-system"/>)

      
</item>

      <item>

        Use a consistent, standard, table of contents for all API documentation

        to maintain familiarity. (<link xref="#standard-layout"/>)

      
</item>

      <item>

        Use <cmd>gdbus-codegen</cmd> to generate D-Bus API documentation to

        include in the gtk-doc build. (<link xref="#dbus-api"/>)

      
</item>

      <item>

        Add introspection annotations to all API documentation.

        (<link xref="#introspection-annotations"/>)

      
</item>

      <item>

        Add Since lines to all API documentation.

        (<link xref="#symbol-versioning"/>)

      
</item>

      <item>

        Enable gtk-doc tests. (<link xref="#keeping-up-to-date"/>)

      
</item>

    </list>

  </synopsis>

  <section id="gtk-doc">

    <title>gtk-doc</title>

      The preferred documentation system for GNOME libraries is 

      href="http://www.gtk.org/gtk-doc/">gtk-doc</link>, which

      extracts inline comments from the code to let you build a 

      href="http://docbook.org/">DocBook</link> document and collection of HTML

      pages.  These can then be read in

      <link href="https://wiki.gnome.org/Apps/Devhelp">Devhelp</link>.  A lot of

      GNOME’s infrastructure is built to handle with documentation written using

      gtk-doc.

  </section>

  <section id="build-system">

    <title>Build System</title>

      To integrate gtk-doc into a project’s build system, follow the

      <link href="https://developer.gnome.org/gtk-doc-manual/stable/settingup.html.en">

      instructions in the gtk-doc manual</link>. Note that while the

      <file>sections.txt</file> file is automatically generated the first time

      gtk-doc is run, it is not generated subsequently, and should be kept up to

      date manually. It should also be

      <link href="https://developer.gnome.org/gtk-doc-manual/stable/settingup_vcs.html.en">

      in version control</link>.

      gtk-doc’s no-tmpl flavour should be used, and XML mode should

      be used instead of SGML. (tmpl mode and SGML are both outdated and slower

      than XML.)

    <comment>

        FIXME: This should be updated once

        https://bugzilla.gnome.org/show_bug.cgi?id=743182 lands.

    </comment>

      If the package version is needed to be substituted into the documentation,

      create a file named <file>docs/version.xml.in</file>, containing:

    @PACKAGE_VERSION@

      Add it to AC_CONFIG_FILES in <file>configure.ac</file>, then

      include it into the main documentation file (<file>*-docs.xml</file>)

      using: <!ENTITY version SYSTEM "version.xml"> in the

      DOCTYPE at the top of the document. The package version can

      then be used inline as &version;.

  </section>

  <section id="standard-layout">

    <title>Standard Layout</title>

      Using a standard layout for the table of contents, sections, appendices,

      etc. means the same <file>project-name-docs.xml</file> template

      can be reused with few changes between projects. It also means the

      documentation layout is similar across all projects, making it more

      familiar to developers.

      The following layout is suggested:

    <listing>

      <title><file>project-name-docs.xml</file></title>

      <desc>A template top-level gtk-doc file for a project</desc>

      <xi:include href="example-docs.xml" parse="text" />

    </listing>

  </section>

  <section id="licensing">

    <title>Licensing</title>

    <comment>

        FIXME: Update this once

        https://bugzilla.gnome.org/show_bug.cgi?id=742580 is fixed.

    </comment>

      It is important to make the license used for API references clear,

      especially if they contain code examples which could be copied around.

      Typically, projects use the same license for their API reference as for 

      the project’s code itself, to avoid confusion. Some other projects use

      CC-BY-SA 3.0 for all their reference documentation. The choice is yours.

      As shown in the <link xref="#standard-layout">Standard Layout</link> you

      should include a <file>license.xml</file> in the top-level gtk-doc DocBook

      file which gives the full text of your documentation license.

  </section>

  <section id="public-api">

    <title>Public APIs</title>

      All public APIs must have gtk-doc comments. For functions, these should

      be placed in the source file, directly above the function.

    /**

 * gtk_get_flow:

 * @widget: a #GtkWidget

 *

 * Gets the flow of a widget.

 *

 * Note that flows may be laminar or turbulent...

 *

 * Returns: (transfer none): the flow of @widget

 */

GtkFlow *

gtk_get_flow (GtkWidget *widget)

{

  ...

}

      Documentation comments for macros, function types, class

      structs, etc. should be placed next to the definitions, typically

      in header files.

      Section introductions should be placed in the source file they describe,

      after the license header:

    /**

 * SECTION:gtksizerequest

 * @Short_Description: Height-for-width geometry management

 * @Title: GtkSizeRequest

 *

 * The GtkSizeRequest interface is GTK+'s height-for-width (and

 * width-for-height) geometry management system.

 * ...

 */

      Keep in mind that in order to include a function, macro,

      function type, or struct type, it needs to be listed in your

      documentation’s <file>modulename-sections.txt</file> file.

      To properly document a new class, it needs to be given its own

      section in <file>modulename-sections.txt</file>, needs to be

      included in your toplevel <file>modulename-docs.sgml</file>,

      and the get_type() function for your class needs

      to be listed in your <file>modulename.types</file>.

  </section>

  <section id="introspection-annotations">

    <title>Introspection Annotations</title>

      Each gtk-doc comment should have appropriate

      <link href="https://wiki.gnome.org/Projects/GObjectIntrospection/Annotations">

      GObject introspection annotations</link>. These are useful for two

      reasons:

    <list type="numbered">

      <item>

        They add important information about parameter types, nullability and

        memory management to the C API documentation generated by gtk-doc.

      
</item>

      <item>

        They allow public APIs to be automatically bound in other languages,

        such as Python or JavaScript.

      
</item>

    </list>

      Introspection annotations add information to APIs (functions, function

      parameters, function return values, structures, GObject properties,

      GObject signals) which is otherwise not present in the machine readable C

      API and only exists in the form of human readable documentation or

      convention. They are very important.

      In gtk-doc comments, annotations should be preferred over human-readable

      equivalents. For example, when documenting a function parameter which may

      be NULL, use the (nullable) annotation rather

      than some text:

    /**

 * my_function:

 * @parameter: (nullable): some parameter which affects something

 *

 * Body of the function documentation.

 */

      Instead of:

    /**

 * my_bad_function:

 * @parameter: some parameter which affects something, or %NULL to ignore

 *

 * Bad body of the function documentation.

 */

      For more information on introspection, see the

      <link xref="introspection">introspection guidelines</link>.

  </section>

  <section id="symbol-versioning">

    <title>Symbol Versioning</title>

      Whenever a symbol is added to the public API, it should have a

      documentation comment added. This comment should always contain a

      Since line with the package version number of the release

      which will first contain the new API. This should be the number currently

      in <file>configure.ac</file> if

      <link xref="versioning#release-process">post-release version

      incrementing</link> is being used.

      For example:

    /**

 * my_function:

 * @param: some parameter

 *

 * Body of the function documentation.

 *

 * Since: 0.5.0

 */

      gtk-doc uses this information to generate indexes of the APIs added in

      each release. These should be added to the main <file>*-docs.xml</file> as

      an appendix:

	<title>Appendices</title>

	<index id="api-index-full">

		<title>API Index</title>

		<xi:include href="xml/api-index-full.xml"><xi:fallback/></xi:include>

	</index>

	<index id="api-index-deprecated">

		<title>Index of deprecated symbols</title>

		<xi:include href="xml/api-index-deprecated.xml"><xi:fallback/></xi:include>

	</index>

	<index role="0.1.0">

		<title>Index of new symbols in 0.1.0</title>

		<xi:include href="xml/api-index-0.1.0.xml"><xi:fallback/></xi:include>

	</index>

	<xi:include href="xml/annotation-glossary.xml"><xi:fallback /></xi:include>

</part>]]>

  </section>

  <section id="dbus-api">

    <title>D-Bus APIs</title>

      D-Bus interface descriptions contain documentation comments, and these can

      be extracted from the XML using <cmd>gdbus-codegen</cmd>, and turned into

      DocBook files to be included by gtk-doc.

    <comment>

        FIXME: Create a page on D-Bus and link to it. Put automake rules to

        generate the documentation somewhere.

    </comment>

      The DocBook files can be included in the main <file>*-docs.xml</file> file

      using:

  <title>C Interfaces</title>

  <partintro>

    <para>C wrappers for the D-Bus interfaces.</para>

  </partintro>

  <xi:include href="xml/SomeDBusService.xml"/>

  <xi:include href="xml/SomeOtherService.xml"/>

</chapter>]]>

      The generated XML files must be included in the content_files

      variable in your gtk-doc <file>Makefile.am</file>, otherwise the build

      will fail. (This is to fix situations where the builddir does

      not equal the srcdir.)

  </section>

  <section id="keeping-up-to-date">

    <title>Keeping Documentation Up to Date</title>

      gtk-doc comes with support for checking the documentation with some basic

      tests. These check that all version indexes are included in the main

      <file>*-docs.xml</file> file and that all symbols are documented, among

      other things.

      These tests should always be enabled, by adding the following to your

      gtk-doc <file>Makefile.am</file>:

    TESTS = $(GTKDOC_CHECK)

      They will then be run as part of <cmd>make check</cmd>.

  </section>

</page>