Media: Optimize images created in shortcodes.

This fixes an issue where images dynamically created during shortcode rendering (e.g., shortcode image galleries), were not getting image optimizations like `loading="lazy"` or `fetchpriority="hight"` applied. Note that even after this commit, shortcodes are processed after the main content images, which can affect the order in which optimizations are applied in content areas.

Follow-up to [56037].

Props spacedmonkey, flixos90, thekt12, swissspidy, joemcgill.
Fixes #58681.

Built from https://develop.svn.wordpress.org/trunk@56214


git-svn-id: http://core.svn.wordpress.org/trunk@55726 1a063a9b-81f0-0310-95a4-ce76da25c4cd

wp-includes/media.php

@@ -5725,9 +5725,10 @@ function wp_get_loading_optimization_attributes( $tag_name, $attr, $context ) {
 
 	/*
 	 * The first elements in 'the_content' or 'the_post_thumbnail' should not be lazy-loaded,
-	 * as they are likely above the fold.
+	 * as they are likely above the fold. Shortcodes are processed after content images, so if
+	 * thresholds haven't already been met, apply the same logic to those as well.
 	 */
-	if ( 'the_content' === $context || 'the_post_thumbnail' === $context ) {
+	if ( 'the_content' === $context || 'the_post_thumbnail' === $context || 'do_shortcode' === $context ) {
 		// Only elements within the main query loop have special handling.
 		if ( is_admin() || ! in_the_loop() || ! is_main_query() ) {
 			$loading_attrs['loading'] = 'lazy';

wp-includes/shortcodes.php

@@ -221,6 +221,14 @@ function do_shortcode( $content, $ignore_html = false ) {
 		return $content;
 	}
 
+	// Ensure this context is only added once if shortcodes are nested.
+	$has_filter = has_filter( 'wp_get_attachment_image_context', '_filter_do_shortcode_context' );
+	$filter_added = false;
+
+	if ( ! $has_filter ) {
+		$filter_added = add_filter( 'wp_get_attachment_image_context', '_filter_do_shortcode_context' );
+	}
+
 	$content = do_shortcodes_in_html_tags( $content, $ignore_html, $tagnames );
 
 	$pattern = get_shortcode_regex( $tagnames );
@@ -229,9 +237,29 @@ function do_shortcode( $content, $ignore_html = false ) {
 	// Always restore square braces so we don't break things like <!--[if IE ]>.
 	$content = unescape_invalid_shortcodes( $content );
 
+	// Only remove the filter if it was added in this scope.
+	if ( $filter_added ) {
+		remove_filter( 'wp_get_attachment_image_context', '_filter_do_shortcode_context' );
+	}
+
 	return $content;
 }
 
+/**
+ * Filter the `wp_get_attachment_image_context` hook during shortcode rendering.
+ *
+ * When wp_get_attachment_image() is called during shortcode rendering, we need to make clear
+ * that the context is a shortcode and not part of the theme's template rendering logic.
+ *
+ * @since 6.3.0
+ * @access private
+ *
+ * @return string The filtered context value for wp_get_attachment_images when doing shortcodes.
+ */
+function _filter_do_shortcode_context() {
+	return 'do_shortcode';
+}
+
 /**
  * Retrieves the shortcode regular expression for searching.
  *

wp-includes/version.php

@@ -16,7 +16,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '6.3-beta3-56213';
+$wp_version = '6.3-beta3-56214';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.