From 3b7eecfc471ed09b9860e79460ca04e42d510fd3 Mon Sep 17 00:00:00 2001
From: Gilles Dubuc <gilles@wikimedia.org>
Date: Wed, 21 Aug 2019 11:04:45 +0200
Subject: [PATCH] Add support for native image lazy loading

Bug: T230897
Depends-On: I6c0b01fafe2c4498852e9c9b81151aba759dc5eb
Change-Id: I0307563b8f433dab062effe4dbfd7d4a9bbb8764
---
 includes/DefaultSettings.php      | 10 ++++++++++
 includes/media/ThumbnailImage.php |  6 +++++-
 2 files changed, 15 insertions(+), 1 deletion(-)

diff --git a/includes/DefaultSettings.php b/includes/DefaultSettings.php
index 98ffe71249..0b14e56ebb 100644
--- a/includes/DefaultSettings.php
+++ b/includes/DefaultSettings.php
@@ -9108,6 +9108,16 @@ $wgFeaturePolicyReportOnly = [];
  */
 $wgSpecialSearchFormOptions = [];
 
+/**
+ * Toggles native image lazy loading, via the "loading" attribute.
+ *
+ * @warning EXPERIMENTAL!
+ *
+ * @since 1.34
+ * @var array
+ */
+$wgNativeImageLazyLoading = false;
+
 /**
  * For really cool vim folding this needs to be at the end:
  * vim: foldmarker=@{,@} foldmethod=marker
diff --git a/includes/media/ThumbnailImage.php b/includes/media/ThumbnailImage.php
index 7ee6dcbee3..6e4412ca8f 100644
--- a/includes/media/ThumbnailImage.php
+++ b/includes/media/ThumbnailImage.php
@@ -110,7 +110,7 @@ class ThumbnailImage extends MediaTransformOutput {
 	 * @return string
 	 */
 	function toHtml( $options = [] ) {
-		global $wgPriorityHints, $wgPriorityHintsRatio, $wgElementTiming;
+		global $wgPriorityHints, $wgPriorityHintsRatio, $wgElementTiming, $wgNativeImageLazyLoading;
 
 		if ( func_num_args() == 2 ) {
 			throw new MWException( __METHOD__ . ' called in the old style' );
@@ -126,6 +126,10 @@ class ThumbnailImage extends MediaTransformOutput {
 			'decoding' => 'async',
 		];
 
+		if ( $wgNativeImageLazyLoading ) {
+			$attribs['loading'] = 'lazy';
+		}
+
 		$elementTimingName = 'thumbnail';
 
 		if ( $wgPriorityHints
-- 
2.20.1