diff -r 07239de796bb -r e756a8c72c3d cms/drupal/sites/all/modules/masonry/masonry.api.php
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/cms/drupal/sites/all/modules/masonry/masonry.api.php	Fri Sep 08 12:04:06 2017 +0200
@@ -0,0 +1,69 @@
+<?php
+/**
+ * @file
+ * Hooks provided by Masonry.
+ */
+
+/**
+ * Alter Masonry's default options.
+ *
+ * @param $options
+ *   An associative array of option names and their default values.
+ */
+function hook_masonry_default_options_alter(&$options) {
+  // Add default value for easing option
+  $options['masonry_animation_easing'] = 'swing';
+}
+
+/**
+ * Alter the form that Masonry options are added to.
+ *
+ * @param $form
+ *   A form array.
+ * @param $default_values
+ *   An array of default form values.
+ */
+function hook_masonry_options_form_alter(&$form, $default_values) {
+  // Add form item for easing option
+  $form['masonry_animation_easing'] = array(
+    '#type' => 'select',
+    '#title' => t('Animation easing'),
+    '#description' => t("The easing function to use for animations."),
+    '#options' => array(
+      'linear' => t('Linear'),
+      'swing' => t('Swing'),
+    ),
+    '#default_value' => $default_values['masonry_animation_easing'],
+    '#states' => array(
+      'visible' => array(
+        'input.form-checkbox[name$="[masonry_resizable]"]' => array('checked' => TRUE),
+        'input.form-checkbox[name$="[masonry_animated]"]' => array('checked' => TRUE),
+      ),
+    ),
+  );
+}
+
+/**
+ * Alter the Masonry script.
+ *
+ * @param $masonry
+ *   An array of Masonry options to send to the script file.
+ * @param $script_file
+ *   A path to the javascript file that triggers Masonry.
+ * @param $context
+ *   An associative array of additional variables.
+ *   Contains:
+ *   - container: The CSS selector of the container element to apply Masonry to.
+ *   - options: An associative array of Masonry options. See masonry_apply().
+ */
+function hook_masonry_script_alter(&$masonry, &$script_file, $context) {
+  $container = $context['container'];
+  $options = $context['options'];
+
+  // Send easing option to the script file
+  $masonry['masonry'][$container]['animation_easing'] = $options['masonry_animation_easing'];
+
+  // Use a custom javascript file that includes easing in the animationOptions
+  $script_file = drupal_get_path('module', '[MODULE_NAME]') . '/custom_masonry.js';
+}
+