function bp_groups_filter_activity_favorites_scope( $retval, $filter ) {
	// Only process for viewers looking at their own favorites feed.
	if ( ! empty( $filter['user_id'] ) ) {
		$user_id = (int) $filter['user_id'];
	} else {
		$user_id = bp_displayed_user_id() ? bp_displayed_user_id() : bp_loggedin_user_id();
	}

	if ( ! $user_id || ! is_user_logged_in() || $user_id !== bp_loggedin_user_id() ) {
		return $retval;
	}

	$favs = bp_activity_get_user_favorites( $user_id );
	if ( empty( $favs ) ) {
		return $retval;
	}

	$user_groups = bp_get_user_groups(
		$user_id,
		array(
			'is_admin' => null,
			'is_mod'   => null,
		)
	);

	$retval = array(
		'relation' => 'OR',

		// Allow hidden items for items unconnected to groups.
		'non_groups' => array(
			'relation' => 'AND',
			array(
				'column'  => 'component',
				'compare' => '!=',
				'value'   => buddypress()->groups->id,
			),
			array(
				'column'  => 'hide_sitewide',
				'compare' => 'IN',
				'value'   => array( 1, 0 ),
			),
			array(
				'column'  => 'id',
				'compare' => 'IN',
				'value'   => $favs,
			),
		),

		// Trust the favorites list for group items that are not hidden sitewide.
		'non_hidden_groups' => array(
			'relation' => 'AND',
			array(
				'column'  => 'component',
				'compare' => '=',
				'value'   => buddypress()->groups->id,
			),
			array(
				'column'  => 'hide_sitewide',
				'compare' => '=',
				'value'   => 0,
			),
			array(
				'column'  => 'id',
				'compare' => 'IN',
				'value'   => $favs,
			),
		),

		// For hidden group items, limit to those in the user's groups.
		'hidden_groups' => array(
			'relation' => 'AND',
			array(
				'column'  => 'component',
				'compare' => '=',
				'value'   => buddypress()->groups->id,
			),
			array(
				'column'  => 'hide_sitewide',
				'compare' => '=',
				'value'   => 1,
			),
			array(
				'column'  => 'id',
				'compare' => 'IN',
				'value'   => $favs,
			),
			array(
				'column'  => 'item_id',
				'compare' => 'IN',
				'value'   => wp_list_pluck( $user_groups, 'group_id' ),
			),
		),

		'override' => array(
			'display_comments' => true,
			'filter'           => array( 'user_id' => 0 ),
			'show_hidden'      => true,
		),
	);

	return $retval;
}