Add an wizard callback listener for the radius field.

Fix readme markup.

Add missing wizard class.

src/EventListener/RadiusWizardCallbackListener.php

@@ -0,0 +1,45 @@
+<?php
+
+/**
+ * Geocode backend widget based on Leaflet.
+ *
+ * @package    netzmacht
+ * @author     David Molineus <david.molineus@netzmacht.de>
+ * @copyright  2016-2018 netzmacht David Molineus. All rights reserved.
+ * @license    LGPL-3.0 https://github.com/netzmacht/contao-leaflet-geocode-widget/blob/master/LICENSE
+ * @filesource
+ */
+
+namespace Netzmacht\Contao\Leaflet\GeocodeWidget\EventListener;
+
+use Contao\DataContainer;
+
+/**
+ * Class RadiusWizardCallbackListener
+ *
+ * @package Netzmacht\Contao\Leaflet\GeocodeWidget\EventListener
+ */
+class RadiusWizardCallbackListener
+{
+    /**
+     * Generate the wizard for the radius widget.
+     *
+     * @param DataContainer $dataContainer Data container driver.
+     *
+     * @return string
+     *
+     * @SuppressWarnings(PHPMD.Superglobals)
+     */
+    public function generateWizard($dataContainer)
+    {
+        if (!isset($GLOBALS['TL_DCA'][$dataContainer->table]['fields'][$dataContainer->field]['eval']['coordinates'])) {
+            return '';
+        }
+
+        return sprintf(
+            '<a href="#" onclick="$(\'ctrl_%s_toggle\').fireEvent(\'click\');return false;"><img src="%s"></a>',
+            $GLOBALS['TL_DCA'][$dataContainer->table]['fields'][$dataContainer->field]['eval']['coordinates'],
+            'bundles/leafletgeocodewidget/img/map.png'
+        );
+    }
+}