BP_Core_oEmbed_Extension::filter_embed_url( string $retval )

	public function filter_embed_url( $retval ) {
		if ( false === isset( buddypress()->{$this->slug_endpoint}->embedurl_in_progress ) && ! $this->is_page() ) {
			return $retval;
		}

		$url = $this->is_page() ? $this->set_permalink() : buddypress()->{$this->slug_endpoint}->embedurl_in_progress;
		$url = trailingslashit( $url );

		// This is for the 'WordPress Embed' block
		// @see bp_activity_embed_comments_button().
		if ( 'the_permalink' !== current_filter() ) {
			$url = add_query_arg( 'embed', 'true', trailingslashit( $url ) );

			// Add custom route args to iframe.
			if ( ! empty( buddypress()->{$this->slug_endpoint}->embedargs_in_progress ) ) {
				foreach( buddypress()->{$this->slug_endpoint}->embedargs_in_progress as $key => $value ) {
					$url = add_query_arg( $key, $value, $url );
				}
			}
		}

		return $url;
	}