Clean Eclipse Preferences Tree with Multiple DSLs

As it is easy to build new domain specific languages (DSLs) with Xtext for Eclipse, enterprise projects may have multiple languages, which are usually related. Each language comes with its own Eclipse preference page, which are by default mixed with other preference pages. A simple way to keep the Eclipse preferences tree clean is to add a root page which aggregates the preference pages for individual (but possibly related) Xtext languages. This can be done by adding the snippet below to a plugin.xml file, for instance to the one of the base DSL's UI project.

<extension
        point="org.eclipse.ui.preferencePages">
    <page
            class="my.dsl.ui.MyDslExecutableExtensionFactory:org.eclipse.xtext.ui.editor.preferences.LanguageRootPreferencePage"
            id="my.id.root.ui"
            name="My DSLs">
        <keywordReference id="my.id.root.ui.keyword_root_pref"/>
    </page>
</extension>

<!-- add keywords for the search in the preferences page -->
<extension
point="org.eclipse.ui.keywords">
<keyword
        id="my.id.root.ui.keyword_root_pref"
        label="other keywords"/>
</extension>

Now, the id of the root page, in this case my.id.root.ui just has to be added to the plugin.xml files of the UI projects of the languages whose preferences should be aggregated. This can also be done in the graphical plugin.xml editor of the DSL's UI projects by navigating to the tab Extensions, selecting the first child node under org.eclipse.ui.preferencePages (which should be the DSL preference page) and pasting my.id.root.ui into the category text box.