feat (*): add default max srcset image width

default-max-srcset-image-width.php

@@ -0,0 +1,51 @@
+<?php
+/*
+Plugin Name: BEA Default - Max Srcset Image Width
+Version: 1.0.0
+Plugin URI: https://beapi.fr
+Description: Set maximum srcset of image width for images markup
+Author: Be API
+Author URI: https://beapi.fr
+
+----
+
+Copyright 2018 Be API Technical team ([email protected])
+
+This program is free software; you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation; either version 2 of the License, or
+(at your option) any later version.
+
+This program is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+GNU General Public License for more details.
+
+You should have received a copy of the GNU General Public License
+along with this program; if not, write to the Free Software
+Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
+
+*/
+namespace BEAPI\Plugin_Defaults\Max_Srcset_Image_Width;
+
+if ( ! defined( 'ABSPATH' ) ) {
+	die( 'Cannot access pages directly.' );
+}
+
+add_filter( 'max_srcset_image_width',  __NAMESPACE__ . '\\optimize_srcset_maximum_width', 10, 2 );
+
+/**
+ * Optimize srcset maximum width contextually
+ * @see https://developer.wordpress.org/reference/hooks/wp_calculate_image_sizes/
+ * instead of using the default max_srcset_image_width of 2048px, we can use a custom value
+ * based on the current image size and multiply it by 2 (or 3) for retina displays
+ * example : In request a 'medium' size of 300px, the max_srcset_image_width will be 600px
+ * in this case, the browser will only load images up to 600px wide if retina.
+ * @param $max_srcset_image_width
+ * @param $sizes_array
+ *
+ * @return float|int
+ */
+function optimize_srcset_maximum_width( $max_srcset_image_width, $sizes_array ) {
+	return $sizes_array[0] * 2;
+}