<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"> <html> <head> <meta http-equiv="Content-Type" content="text/html; charset=UTF-8"> <title>Schema conversion: GIO Reference Manual</title> <meta name="generator" content="DocBook XSL Stylesheets V1.79.1"> <link rel="home" href="index.html" title="GIO Reference Manual"> <link rel="up" href="ch34.html" title="Migrating from GConf to GSettings"> <link rel="prev" href="ch34s05.html" title="Change sets"> <link rel="next" href="ch34s07.html" title="Data conversion"> <meta name="generator" content="GTK-Doc V1.25.1 (XML mode)"> <link rel="stylesheet" href="style.css" type="text/css"> </head> <body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"> <table class="navigation" id="top" width="100%" summary="Navigation header" cellpadding="2" cellspacing="5"><tr valign="middle"> <td width="100%" align="left" class="shortcuts"></td> <td><a accesskey="h" href="index.html"><img src="home.png" width="16" height="16" border="0" alt="Home"></a></td> <td><a accesskey="u" href="ch34.html"><img src="up.png" width="16" height="16" border="0" alt="Up"></a></td> <td><a accesskey="p" href="ch34s05.html"><img src="left.png" width="16" height="16" border="0" alt="Prev"></a></td> <td><a accesskey="n" href="ch34s07.html"><img src="right.png" width="16" height="16" border="0" alt="Next"></a></td> </tr></table> <div class="section"> <div class="titlepage"><div><div><h2 class="title" style="clear: both"> <a name="id-1.5.4.7"></a>Schema conversion</h2></div></div></div> <p> If you are porting your application from GConf, most likely you already have a GConf schema. GConf comes with a commandline tool gsettings-schema-convert that can help with the task of converting a GConf schema into an equivalent GSettings schema. The tool is not perfect and may need assistence in some cases. </p> <div class="example"> <a name="id-1.5.4.7.3"></a><p class="title"><b>Example 1. An example for using gsettings-schema-convert</b></p> <div class="example-contents"> <p>Running <strong class="userinput"><code>gsettings-schema-convert --gconf --xml --schema-id "org.gnome.font-rendering" --output org.gnome.font-rendering.gschema.xml destop_gnome_font_rendering.schemas</code></strong> on the following <code class="filename">desktop_gnome_font_rendering.schemas</code> file: </p> <pre class="programlisting"> <?xml version="1.0"?> <gconfschemafile> <schemalist> <schema> <key>/schemas/desktop/gnome/font_rendering/dpi</key> <applyto>/desktop/gnome/font_rendering/dpi</applyto> <owner>gnome</owner> <type>int</type> <default>96</default> <locale name="C"> <short>DPI</short> <long>The resolution used for converting font sizes to pixel sizes, in dots per inch.</long> </locale> </schema> </schemalist> </gconfschemafile> </pre> <p> produces a <code class="filename">org.gnome.font-rendering.gschema.xml</code> file with the following content: </p> <pre class="programlisting"> <schemalist> <schema id="org.gnome.font-rendering" path="/desktop/gnome/font_rendering/"> <key name="dpi" type="i"> <default>96</default> <summary>DPI</summary> <description>The resolution used for converting font sizes to pixel sizes, in dots per inch.</description> </key> </schema> </schemalist> </pre> <p> </p> </div> </div> <br class="example-break"><p> GSettings schemas are identified at runtime by their id (as specified in the XML source file). It is recommended to use a dotted name as schema id, similar in style to a D-Bus bus name, e.g. "org.gnome.SessionManager". In cases where the settings are general and not specific to one application, the id should not use StudlyCaps, e.g. "org.gnome.font-rendering". The filename used for the XML schema source is immaterial, but schema compiler expects the files to have the extension <code class="filename">.gschema.xml</code>. It is recommended to simply use the schema id as the filename, followed by this extension, e.g. <code class="filename">org.gnome.SessionManager.gschema.xml</code>. </p> <p> The XML source file for your GSettings schema needs to get installed into <code class="filename">$datadir/glib-2.0/schemas</code>, and needs to be compiled into a binary form. At runtime, GSettings looks for compiled schemas in the <code class="filename">glib-2.0/schemas</code> subdirectories of all <code class="envar">XDG_DATA_DIRS</code> directories, so if you install your schema in a different location, you need to set the <code class="envar">XDG_DATA_DIRS</code> environment variable appropriately. </p> <p> Schemas are compiled into binary form by the glib-compile-schemas utility. GIO provides a <code class="literal">glib_compile_schemas</code> variable for the schema compiler. </p> <p> You can ignore all of this by using the provided m4 macros. To do this, add to your <code class="filename">configure.ac</code>: </p> <pre class="programlisting"> GLIB_GSETTINGS </pre> <p> The corresponding <code class="filename">Makefile.am</code> fragment looks like this: </p> <pre class="programlisting"> # gsettings_SCHEMAS is a list of all the schemas you want to install gsettings_SCHEMAS = my.app.gschema.xml # include the appropriate makefile rules for schema handling @GSETTINGS_RULES@ </pre> <p> </p> <p> This is not sufficient on its own. You need to mention what the source of the <code class="filename">my.app.gschema.xml</code> file is. If the schema file is distributed directly with your project's tarball then a mention in <code class="varname">EXTRA_DIST</code> is appropriate. If the schema file is generated from another source then you will need the appropriate rule for that, plus probably an item in <code class="varname">EXTRA_DIST</code> for the source files used by that rule. </p> <p> One possible pitfall in doing schema conversion is that the default values in GSettings schemas are parsed by the <a href="../glib-GVariant.html#GVariant"><span class="type">GVariant</span></a> parser. This means that strings need to include quotes in the XML. Also note that the types are now specified as <a href="../glib-GVariant.html#GVariant"><span class="type">GVariant</span></a> type strings. </p> <pre class="programlisting"> <type>string</type> <default>rgb</default> </pre> <p> becomes </p> <pre class="programlisting"> <key name="rgba-order" type="s"> <default>'rgb'</default> <!-- note quotes --> </key> </pre> <p> </p> <p> Another possible complication is that GConf specifies full paths for each key, while a GSettings schema has a 'path' attribute that contains the prefix for all the keys in the schema, and individual keys just have a simple name. So </p> <pre class="programlisting"> <key>/schemas/desktop/gnome/font_rendering/antialiasing</key> </pre> <p> becomes </p> <pre class="programlisting"> <schema id="org.gnome.font" path="/desktop/gnome/font_rendering/"> <key name="antialiasing" type="s"> </pre> <p> </p> <p> Default values can be localized in both GConf and GSettings schemas, but GSettings uses gettext for the localization. You can specify the gettext domain to use in the <code class="sgmltag-attribute">gettext-domain</code> attribute. Therefore, when converting localized defaults in GConf, </p> <pre class="programlisting"> <key>/schemas/apps/my_app/font_size</key> <locale name="C"> <default>18</default> </locale> <locale name="be"> <default>24</default> </locale> </key> </pre> <p> becomes </p> <pre class="programlisting"> <schema id="..." gettext-domain="your-domain"> ... <key name="font-size" type="i"> <default l10n="messages" context="font_size">18</default> </key> </pre> <p> </p> <p> GSettings uses gettext for translation of default values. The string that is translated is exactly the string that appears inside of the <code class="sgmltag-starttag"><default></code> element. This includes the quotation marks that appear around strings. Default values must be marked with the <code class="varname">l10n</code> attribute in the <code class="sgmltag-starttag"><default></code> tag, which should be set as equal to <code class="literal">'messages'</code> or <code class="literal">'time'</code> depending on the desired category. An optional translation context can also be specified with the <code class="varname">context</code> attribute, as in the example. This is usually recommended, since the string "<code class="literal">18</code>" is not particularly easy to translate without context. The translated version of the default value should be stored in the specified <code class="varname">gettext-domain</code>. Care must be taken during translation to ensure that all translated values remain syntactically valid; mistakes here will cause runtime errors. </p> <p> GSettings schemas have optional <code class="sgmltag-starttag"><summary></code> and <code class="sgmltag-starttag"><description></code> elements for each key which correspond to the <code class="sgmltag-starttag"><short></code> and <code class="sgmltag-starttag"><long></code> elements in the GConf schema and will be used in similar ways by a future gsettings-editor, so you should use the same conventions for them: The summary is just a short label with no punctuation, the description can be one or more complete sentences. If multiple paragraphs are desired for the description, the paragraphs should be separated by a completely empty line. </p> <p> Translations for these strings will also be handled via gettext, so you should arrange for these strings to be extracted into your gettext catalog. One way to do that is to use intltool. Since intltool 0.50.1, schema files are supported, so all you have to do is to add your .gschema.xml files to <code class="filename">POTFILES.in</code> with a line like </p> <pre class="programlisting"> [type: gettext/gsettings]data/org.foo.MyApp.gschema.xml </pre> <p> </p> <p> GSettings is a bit more restrictive about key names than GConf. Key names in GSettings can be at most 32 characters long, and must only consist of lowercase characters, numbers and dashes, with no consecutive dashes. The first character must not be a number or dash, and the last character cannot be '-'. </p> <p> If you are using the GConf backend for GSettings during the transition, you may want to keep your key names the same they were in GConf, so that existing settings in the users GConf database are preserved. You can achieve this by using the <code class="option">--allow-any-name</code> with the glib-compile-schemas schema compiler. Note that this option is only meant to ease the process of porting your application, allowing parts of your application to continue to access GConf and parts to use GSettings. By the time you have finished porting your application you must ensure that all key names are valid. </p> </div> <div class="footer"> <hr>Generated by GTK-Doc V1.25.1</div> </body> </html>