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wp_get_loading_attr_default › WordPress Function

Since5.9.0
Deprecated6.3.0
› wp_get_loading_attr_default ( $context )
Parameters:
  • (string) $context Context for the element for which the `loading` attribute value is requested.
    Required: Yes
See:
Returns:
  • (string|bool) The default `loading` attribute value. Either 'lazy', 'eager', or a boolean `false`, to indicate that the `loading` attribute should be skipped.
Defined at:
Codex:

Gets the default value to use for a `loading` attribute on an element.

This function should only be called for a tag and context if lazy-loading is generally enabled. The function usually returns 'lazy', but uses certain heuristics to guess whether the current element is likely to appear above the fold, in which case it returns a boolean false, which will lead to the loading attribute being omitted on the element. The purpose of this refinement is to avoid lazy-loading elements that are within the initial viewport, which can have a negative performance impact. Under the hood, the function uses {@see} every time it is called for an element within the main content. If the element is the very first content element, the loading attribute will be omitted. This default threshold of 3 content elements to omit the loading attribute for can be customized using the {@see 'wp_omit_loading_attr_threshold'} filter.


Related Functions: wp_get_widget_defaults, get_metadata_default, wp_omit_loading_attr_threshold, wp_img_tag_add_loading_attr, _get_admin_bar_pref

Source 

function wp_get_loading_attr_default( $context ) {
	_deprecated_function( __FUNCTION__, '6.3.0', 'wp_get_loading_optimization_attributes()' );
	global $wp_query;

	// Skip lazy-loading for the overall block template, as it is handled more granularly.
	if ( 'template' === $context ) {
		return false;
	}

	/*
	 * Do not lazy-load images in the header block template part, as they are likely above the fold.
	 * For classic themes, this is handled in the condition below using the 'get_header' action.
	 */
	$header_area = WP_TEMPLATE_PART_AREA_HEADER;
	if ( "template_part_{$header_area}" === $context ) {
		return false;
	}

	// Special handling for programmatically created image tags.
	if ( 'the_post_thumbnail' === $context || 'wp_get_attachment_image' === $context ) {
		/*
		 * Skip programmatically created images within post content as they need to be handled together with the other
		 * images within the post content.
		 * Without this clause, they would already be counted below which skews the number and can result in the first
		 * post content image being lazy-loaded only because there are images elsewhere in the post content.
		 */
		if ( doing_filter( 'the_content' ) ) {
			return false;
		}

		// Conditionally skip lazy-loading on images before the loop.
		if (
			// 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' )
		) {
			return false;
		}
	}

	/*
	 * The first elements in 'the_content' or 'the_post_thumbnail' should not be lazy-loaded,
	 * as they are likely above the fold.
	 */
	if ( 'the_content' === $context || 'the_post_thumbnail' === $context ) {
		// Only elements within the main query loop have special handling.
		if ( is_admin() || ! in_the_loop() || ! is_main_query() ) {
			return 'lazy';
		}

		// Increase the counter since this is a main query content element.
		$content_media_count = wp_increase_content_media_count();

		// If the count so far is below the threshold, return `false` so that the `loading` attribute is omitted.
		if ( $content_media_count <= wp_omit_loading_attr_threshold() ) {
			return false;
		}

		// For elements after the threshold, lazy-load them as usual.
		return 'lazy';
	}

	// Lazy-load by default for any unknown context.
	return 'lazy';
}