From 8e11c5dabc56f5bc0127054ae65735cbfcc62258 Mon Sep 17 00:00:00 2001
From: Gilles Dubuc <gilles@wikimedia.org>
Date: Wed, 20 Feb 2019 15:06:36 +0100
Subject: [PATCH] Add Priority Hints support

When the option is enabled, the first non-icon
thumbnail encountered has a "high" importance.

Bug: T216499
Change-Id: I8d3c1b3e2d136ba16bd7de4809ee3ca63ab462fe
---
 includes/DefaultSettings.php            | 10 ++++++++++
 includes/media/MediaTransformOutput.php | 12 ++++++++++++
 2 files changed, 22 insertions(+)

diff --git a/includes/DefaultSettings.php b/includes/DefaultSettings.php
index 1761b00778..717b7b67a5 100644
--- a/includes/DefaultSettings.php
+++ b/includes/DefaultSettings.php
@@ -9027,6 +9027,16 @@ $wgEnableBlockNoticeStats = false;
  */
 $wgOriginTrials = [];
 
+/**
+ * Enable client-side Priority Hints.
+ *
+ * @warning EXPERIMENTAL!
+ *
+ * @since 1.34
+ * @var bool
+ */
+$wgPriorityHints = false;
+
 /**
  * For really cool vim folding this needs to be at the end:
  * vim: foldmarker=@{,@} foldmethod=marker
diff --git a/includes/media/MediaTransformOutput.php b/includes/media/MediaTransformOutput.php
index 12048a9012..34f7e8cb76 100644
--- a/includes/media/MediaTransformOutput.php
+++ b/includes/media/MediaTransformOutput.php
@@ -275,6 +275,8 @@ abstract class MediaTransformOutput {
  * @ingroup Media
  */
 class ThumbnailImage extends MediaTransformOutput {
+	private static $firstNonIconImageRendered = false;
+
 	/**
 	 * Get a thumbnail object from a file and parameters.
 	 * If $path is set to null, the output file is treated as a source copy.
@@ -356,6 +358,8 @@ class ThumbnailImage extends MediaTransformOutput {
 	 * @return string
 	 */
 	function toHtml( $options = [] ) {
+		global $wgPriorityHints;
+
 		if ( count( func_get_args() ) == 2 ) {
 			throw new MWException( __METHOD__ . ' called in the old style' );
 		}
@@ -370,6 +374,14 @@ class ThumbnailImage extends MediaTransformOutput {
 			'decoding' => 'async',
 		];
 
+		if ( $wgPriorityHints
+			&& !self::$firstNonIconImageRendered
+			&& $this->width * $this->height > 100 * 100 ) {
+			self::$firstBigImageRendered = true;
+
+			$attribs['importance'] = 'high';
+		}
+
 		if ( !empty( $options['custom-url-link'] ) ) {
 			$linkAttribs = [ 'href' => $options['custom-url-link'] ];
 			if ( !empty( $options['title'] ) ) {
-- 
2.20.1