y-loaded and marked as high priority at the same time.' ),
				'6.3.0'
			);
			/*
			 * Set `fetchpriority` here for backward-compatibility as we should
			 * not override what a developer decided, even though it seems
			 * incorrect.
			 */
			$loading_attrs['fetchpriority'] = 'high';
		} else {
			$maybe_in_viewport = true;
		}
	}

	if ( null === $maybe_in_viewport ) {
		$header_enforced_contexts = array(
			'template_part_' . WP_TEMPLATE_PART_AREA_HEADER => true,
			'get_header_image_tag' => true,
		);

		/**
		 * Filters the header-specific contexts.
		 *
		 * @since 6.4.0
		 *
		 * @param array $default_header_enforced_contexts Map of contexts for which elements should be considered
		 *                                                in the header of the page, as $context => $enabled
		 *                                                pairs. The $enabled should always be true.
		 */
		$header_enforced_contexts = apply_filters( 'wp_loading_optimization_force_header_contexts', $header_enforced_contexts );

		// Consider elements with these header-specific contexts to be in viewport.
		if ( isset( $header_enforced_contexts[ $context ] ) ) {
			$maybe_in_viewport    = true;
			$maybe_increase_count = true;
		} elseif ( ! is_admin() && in_the_loop() && is_main_query() ) {
			/*
			 * Get the content media count, since this is a main query
			 * content element. This is accomplished by "increasing"
			 * the count by zero, as the only way to get the count is
			 * to call this function.
			 * The actual count increase happens further below, based
			 * on the `$increase_count` flag set here.
			 */
			$content_media_count = wp_increase_content_media_count( 0 );
			$increase_count      = true;

			// If the count so far is below the threshold, `loading` attribute is omitted.
			if ( $content_media_count < wp_omit_loading_attr_threshold() ) {
				$maybe_in_viewport = true;
			} else {
				$maybe_in_viewport = false;
			}
		} elseif (
			// Only apply for main query but before the loop.
			$wp_query->before_loop && $wp_query->is_main_query()
			/*
			 * Any image before the loop, but after the header has started should not be lazy-loaded,
			 * except when the footer has already started which can happen when the current template
			 * does not include any loop.
			 */
			&& did_action( 'get_header' ) && ! did_action( 'get_footer' )
			) {
			$maybe_in_viewport    = true;
			$maybe_increase_count = true;
		}
	}

	/*
	 * If the element is in the viewport (`true`), potentially add
	 * `fetchpriority` with a value of "high". Otherwise, i.e. if the element
	 * is not not in the viewport (`false`) or it is unknown (`null`), add
	 * `loading` with a value of "lazy".
	 */
	if ( $maybe_in_viewport ) {
		$loading_attrs = wp_maybe_add_fetchpriority_high_attr( $loading_attrs, $tag_name, $attr );
	} else {
		// Only add `loading="lazy"` if the feature is enabled.
		if ( wp_lazy_loading_enabled( $tag_name, $context ) ) {
			$loading_attrs['loading'] = 'lazy';
		}
	}

	/*
	 * If flag was set based on contextual logic above, increase the content
	 * media count, either unconditionally, or based on whether the image size
	 * is larger than the threshold.
	 */
	if ( $increase_count ) {
		wp_increase_content_media_count();
	} elseif ( $maybe_increase_count ) {
		/** This filter is documented in wp-includes/media.php */
		$wp_min_priority_img_pixels = apply_filters( 'wp_min_priority_img_pixels', 50000 );

		if ( $wp_min_priority_img_pixels <= $attr['width'] * $attr['height'] ) {
			wp_increase_content_media_count();
		}
	}

	/**
	 * Filters the loading optimization attributes.
	 *
	 * @since 6.4.0
	 *
	 * @param array  $loading_attrs The loading optimization attributes.
	 * @param string $tag_name      The tag name.
	 * @param array  $attr          Array of the attributes for the tag.
	 * @param string $context       Context for the element for which the loading optimization attribute is requested.
	 */
	return apply_filters( 'wp_get_loading_optimization_attributes', $loading_attrs, $tag_name, $attr, $context );
}

/**
 * Gets the threshold for how many of the first content media elements to not lazy-load.
 *
 * This function runs the {@see 'wp_omit_loading_attr_threshold'} filter, which uses a default threshold value of 3.
 * The filter is only run once per page load, unless the `$force` parameter is used.
 *
 * @since 5.9.0
 *
 * @param bool $force Optional. If set to true, the filter will be (re-)applied even if it already has been before.
 *                    Default false.
 * @return int The number of content media elements to not lazy-load.
 */
function wp_omit_loading_attr_threshold( $force = false ) {
	static $omit_threshold;

	// This function may be called multiple times. Run the filter only once per page load.
	if ( ! isset( $omit_threshold ) || $force ) {
		/**
		 * Filters the threshold for how many of the first content media elements to not lazy-load.
		 *
		 * For these first content media elements, the `loading` attribute will be omitted. By default, this is the case
		 * for only the very first content media element.
		 *
		 * @since 5.9.0
		 * @since 6.3.0 The default threshold was changed from 1 to 3.
		 *
		 * @param int $omit_threshold The number of media elements where the `loading` attribute will not be added. Default 3.
		 */
		$omit_threshold = apply_filters( 'wp_omit_loading_attr_threshold', 3 );
	}

	return $omit_threshold;
}

/**
 * Increases an internal content media count variable.
 *
 * @since 5.9.0
 * @access private
 *
 * @param int $amount Optional. Amount to increase by. Default 1.
 * @return int The latest content media count, after the increase.
 */
function wp_increase_content_media_count( $amount = 1 ) {
	static $content_media_count = 0;

	$content_media_count += $amount;

	return $content_media_count;
}

/**
 * Determines whether to add `fetchpriority='high'` to loading attributes.
 *
 * @since 6.3.0
 * @access private
 *
 * @param array  $loading_attrs Array of the loading optimization attributes for the element.
 * @param string $tag_name      The tag name.
 * @param array  $attr          Array of the attributes for the element.
 * @return array Updated loading optimization attributes for the element.
 */
function wp_maybe_add_fetchpriority_high_attr( $loading_attrs, $tag_name, $attr ) {
	// For now, adding `fetchpriority="high"` is only supported for images.
	if ( 'img' !== $tag_name ) {
		return $loading_attrs;
	}

	if ( isset( $attr['fetchpriority'] ) ) {
		/*
		 * While any `fetchpriority` value could be set in `$loading_attrs`,
		 * for consistency we only do it for `fetchpriority="high"` since that
		 * is the only possible value that WordPress core would apply on its
		 * own.
		 */
		if ( 'high' === $attr['fetchpriority'] ) {
			$loading_attrs['fetchpriority'] = 'high';
			wp_high_priority_element_flag( false );
		}

		return $loading_attrs;
	}

	// Lazy-loading and `fetchpriority="high"` are mutually exclusive.
	if ( isset( $loading_attrs['loading'] ) && 'lazy' === $loading_attrs['loading'] ) {
		return $loading_attrs;
	}

	if ( ! wp_high_priority_element_flag() ) {
		return $loading_attrs;
	}

	/**
	 * Filters the minimum square-pixels threshold for an image to be eligible as the high-priority image.
	 *
	 * @since 6.3.0
	 *
	 * @param int $threshold Minimum square-pixels threshold. Default 50000.
	 */
	$wp_min_priority_img_pixels = apply_filters( 'wp_min_priority_img_pixels', 50000 );

	if ( $wp_min_priority_img_pixels <= $attr['width'] * $attr['height'] ) {
		$loading_attrs['fetchpriority'] = 'high';
		wp_high_priority_element_flag( false );
	}

	return $loading_attrs;
}

/**
 * Accesses a flag that indicates if an element is a possible candidate for `fetchpriority='high'`.
 *
 * @since 6.3.0
 * @access private
 *
 * @param bool $value Optional. Used to change the static variable. Default null.
 * @return bool Returns true if high-priority element was marked already, otherwise false.
 */
function wp_high_priority_element_flag( $value = null ) {
	static $high_priority_element = true;

	if ( is_bool( $value ) ) {
		$high_priority_element = $value;
	}

	return $high_priority_element;
}

/**
 * Determines the output format for the image editor.
 *
 * @since 6.7.0
 * @access private
 *
 * @param string $filename  Path to the image.
 * @param string $mime_type The source image mime type.
 * @return string[] An array of mime type mappings.
 */
function wp_get_image_editor_output_format( $filename, $mime_type ) {
	$output_format = array(
		'image/heic'          => 'image/jpeg',
		'image/heif'          => 'image/jpeg',
		'image/heic-sequence' => 'image/jpeg',
		'image/heif-sequence' => 'image/jpeg',
	);

	/**
	 * Filters the image editor output format mapping.
	 *
	 * Enables filtering the mime type used to save images. By default HEIC/HEIF images
	 * are converted to JPEGs.
	 *
	 * @see WP_Image_Editor::get_output_format()
	 *
	 * @since 5.8.0
	 * @since 6.7.0 The default was changed from an empty array to an array
	 *              containing the HEIC/HEIF images mime types.
	 *
	 * @param string[] $output_format {
	 *     An array of mime type mappings. Maps a source mime type to a new
	 *     destination mime type. By default maps HEIC/HEIF input to JPEG output.
	 *
	 *     @type string ...$0 The new mime type.
	 * }
	 * @param string $filename  Path to the image.
	 * @param string $mime_type The source image mime type.
	 */
	return apply_filters( 'image_editor_output_format', $output_format, $filename, $mime_type );
}