[Theme] Documentation for theme settings

docs/bundles/SyliusThemeBundle/index.rst

@@ -9,5 +9,6 @@ Flexible theming system for Symfony2 applications.
     installation
     important_changes
     your_first_theme
+    theme_settings
     theme_configuration_reference
     summary

docs/bundles/SyliusThemeBundle/theme_settings.rst

@@ -0,0 +1,78 @@
+Theme settings
+==============
+
+ThemeBundle has built-in, optional integration with `SettingsBundle </en/latest/bundles/SyliusSettingsBundle.html>`_.
+
+Installation and configuration
+------------------------------
+
+In order to start using settings for your themes, you should `install SettingsBundle </en/latest/bundles/SyliusSettingsBundle/installation.html>`_ first.
+
+Theme settings schema
+---------------------
+
+Theme settings schema should be saved in ``Settings.php`` file in your theme's main directory. The file should
+**return** an instance of ``SchemaInterface``. The example settings file looks like:
+
+PHP 5
+~~~~~
+
+.. code-block:: php
+
+    <?php // app/themes/AcmeTheme/Settings.php
+
+    use Sylius\Bundle\SettingsBundle\Schema\CallbackSchema;
+    use Sylius\Bundle\SettingsBundle\Schema\SettingsBuilderInterface;
+    use Symfony\Component\Form\FormBuilderInterface;
+
+    return new CallbackSchema(
+        function (SettingsBuilderInterface $settingsBuilder) {
+            // define your settings here, e.g.
+            $settingsBuilder->setDefault('option', 'foo');
+        },
+        function (FormBuilderInterface $formBuilder) {
+            // define your form type here, e.g.
+            $formBuilder->add('option', 'text');
+        }
+    );
+
+.. note::
+
+    Do not define your custom class in the global namespace, as it may cause conflicts if there are more classes named the same.
+
+PHP 7
+~~~~~
+
+.. code-block:: php
+
+    <?php // app/themes/AcmeTheme/Settings.php
+
+    use Sylius\Bundle\SettingsBundle\Schema\SchemaInterface;
+    use Sylius\Bundle\SettingsBundle\Schema\SettingsBuilderInterface;
+    use Symfony\Component\Form\FormBuilderInterface;
+
+    return new class implements SchemaInterface {
+        public function buildSettings(SettingsBuilderInterface $builder)
+        {
+            // define your settings here, e.g.
+            $settingsBuilder->setDefault('option', 'foo');
+        }
+
+        public function buildForm(FormBuilderInterface $builder)
+        {
+            // define your form type here, e.g.
+            $formBuilder->add('option', 'text');
+        }
+    }
+
+Using theme settings in your templates
+--------------------------------------
+
+Configured theme settings can be easily get in theme templates by using ``sylius_theme_settings()`` Twig function,
+which works just the same as ``sylius_settings('schema')`` function from vanilla SettingsBundle.
+
+.. code-block:: twig
+
+    {% if sylius_theme_settings().showThisDiv %}
+        <div>Hidden div!</div>
+    {% endif %}