Document extension points and environment variables

docs/reference/gio/overview.xml

@@ -248,6 +248,37 @@
       </para>
     </formalpara>
 
+    <formalpara>
+      <title><envar>GSETTINGS_BACKEND</envar></title>
+
+      <para>
+        This variable can be set to the name of a #GSettingsBackend
+        implementation to override the default for debugging purposes.
+        The keyfile-based implementation that is included in GIO has
+        the name "memory", the one in dconf has the name "dconf-settings".
+      </para>
+    </formalpara>
+
+    <formalpara>
+      <title><envar>GSETTINGS_SCHEMA_DIR</envar></title>
+
+      <para>
+        This variable can be set to the name of a directory that is
+        considered in addition to the <filename>glib-2.0/schemas</filename>
+        subdirectories of the XDG system data dirs when looking
+        for compiled schemas for #GSettings.
+      </para>
+    </formalpara>
+
+    <formalpara>
+      <title><envar>GSETTINGS_MEMORY_BACKEND_STORE</envar></title>
+
+      <para>
+        This variable can be set to the path where the built-in #GSettings
+        backend stores its keyfile. By default, the keyfile is stored in
+        <filename>$HOME/.config/gsettings/store</filename>.
+      </para>
+    </formalpara>
   </chapter>
 
   <chapter id="extending-gio">
@@ -355,5 +386,17 @@
         same GConf keys as gnome-vfs.
       </para>
    </formalpara>
+
+   <formalpara>
+      <title>G_SETTINGS_BACKEND_EXTENSION_POINT_NAME</title>
+
+      <para>
+        Allows to provide an alternative storage for #GSettings.
+        Implementations of this extension point must derive from the
+        #GSettingsBackend type. GIO contains a keyfile-based
+        implementation of this extension point, another one is provided
+        by dconf.
+      </para>
+   </formalpara>
   </chapter>
 </part>