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Description

Gets loading optimization attributes.

This function returns an array of attributes that should be merged into the given attributes array to optimize loading performance. Potential attributes returned by this function are:

• `loading` attribute with a value of "lazy"
• `fetchpriority` attribute with a value of "high"
• `decoding` attribute with a value of "async"

If any of these attributes are already present in the given attributes, they will not be modified. Note that no element should have both loading="lazy" and `fetchpriority="high"`, so the function will trigger a warning in case both attributes are present with those values.

Usage

$array = wp_get_loading_optimization_attributes( $tag_name, $attr, $context );

Parameters

$tag_name

( string ) required – The tag name.

$attr

( array ) required – Array of the attributes for the tag.

$context

( string ) required – Context for the element for which the loading optimization attribute is requested.

Returns

array Loading optimization attributes.

Source

File name: wordpress/wp-includes/media.php
Lines:

function wp_get_loading_optimization_attributes( $tag_name, $attr, $context ) {
  global $wp_query;

  
/**
 * Filters whether to short-circuit loading optimization attributes.
 *
 * Returning an array from the filter will effectively short-circuit the loading of optimization attributes,
 * returning that value instead.
 *
 * @since 6.4.0
 *
 * @param array|false $loading_attrs False by default, or array of loading optimization attributes to short-circuit.
 * @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.
 */
  $loading_attrs = apply_filters( 'pre_wp_get_loading_optimization_attributes', false, $tag_name, $attr, $context );

  if ( is_array( $loading_attrs ) ) {
    return $loading_attrs;
  }

  $loading_attrs = array();

  /*
	 * Skip lazy-loading for the overall block template, as it is handled more granularly.
	 * The skip is also applicable for `fetchpriority`.
	 */
  if ( 'template' === $context ) {
    
/** This filter is documented in wp-includes/media.php */
    return apply_filters( 'wp_get_loading_optimization_attributes', $loading_attrs, $tag_name, $attr, $context );
  }

  // For now this function only supports images and iframes.
  if ( 'img' !== $tag_name && 'iframe' !== $tag_name ) {
    
/** This filter is documented in wp-includes/media.php */
    return apply_filters( 'wp_get_loading_optimization_attributes', $loading_attrs, $tag_name, $attr, $context );
  }

  /*
	 * Skip programmatically created images within content blobs as they need to be handled together with the other
	 * images within the post content or widget content.
	 * Without this clause, they would already be considered within their own context which skews the image count and
	 * can result in the first post content image being lazy-loaded or an image further down the page being marked as a
	 * high priority.
	 */
  if (
    'the_content' !== $context && doing_filter( 'the_content' ) ||
    'widget_text_content' !== $context && doing_filter( 'widget_text_content' ) ||
    'widget_block_content' !== $context && doing_filter( 'widget_block_content' )
  ) {
    
/** This filter is documented in wp-includes/media.php */
    return apply_filters( 'wp_get_loading_optimization_attributes', $loading_attrs, $tag_name, $attr, $context );

  }

  /*
	 * Add `decoding` with a value of "async" for every image unless it has a
	 * conflicting `decoding` attribute already present.
	 */
  if ( 'img' === $tag_name ) {
    if ( isset( $attr['decoding'] ) ) {
      $loading_attrs['decoding'] = $attr['decoding'];
    } else {
      $loading_attrs['decoding'] = 'async';
    }
  }

  // For any resources, width and height must be provided, to avoid layout shifts.
  if ( ! isset( $attr['width'], $attr['height'] ) ) {
    
/** This filter is documented in wp-includes/media.php */
    return apply_filters( 'wp_get_loading_optimization_attributes', $loading_attrs, $tag_name, $attr, $context );
  }

  /*
	 * The key function logic starts here.
	 */
  $maybe_in_viewport    = null;
  $increase_count       = false;
  $maybe_increase_count = false;

  // Logic to handle a `loading` attribute that is already provided.
  if ( isset( $attr['loading'] ) ) {
    /*
		 * Interpret "lazy" as not in viewport. Any other value can be
		 * interpreted as in viewport (realistically only "eager" or `false`
		 * to force-omit the attribute are other potential values).
		 */
    if ( 'lazy' === $attr['loading'] ) {
      $maybe_in_viewport = false;
    } else {
      $maybe_in_viewport = true;
    }
  }

  // Logic to handle a `fetchpriority` attribute that is already provided.
  if ( isset( $attr['fetchpriority'] ) && 'high' === $attr['fetchpriority'] ) {
    /*
		 * If the image was already determined to not be in the viewport (e.g.
		 * from an already provided `loading` attribute), trigger a warning.
 

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