lized fired just before making LazyLoad global
				// so next execution cycle have it
				$on_initialized_javascript_wrapped =
					'window.addEventListener("LazyLoad::Initialized", function(){' .
						'setTimeout(function() {' .
							$on_initialized_javascript .
						'}, 1);' .
					'});';
			}

			$embed_script =
				'<style>img.lazy{min-height:1px}</style>' .
				'<link rel="preload" href="' . esc_url( $js_url ) . '" as="script">';

			$buffer = preg_replace( '~<head(\s+[^>]*)*>~Ui',
				'\\0' . $embed_script, $buffer, 1 );

			// load lazyload in footer to make sure DOM is ready at the moment of initialization
			$footer_script =
				'<script>' .
					$on_initialized_javascript_wrapped .
					'window.w3tc_lazyload=1,' .
					'window.lazyLoadOptions=' . $config .
				'</script>' .
				'<script async src="' . esc_url( $js_url ) . '"></script>';
			$buffer = preg_replace( '~</body(\s+[^>]*)*>~Ui',
				$footer_script . '\\0', $buffer, 1 );

		} elseif ( $method == 'inline_footer' ) {
			$footer_script =
				'<style>img.lazy{min-height:1px}</style>' .
				'<script>' .
				file_get_contents( W3TC_DIR . '/pub/js/lazyload.min.js' ) .
				'window.w3tc_lazyload=new LazyLoad(' . $config . ');' .
				$on_initialized_javascript .
				'</script>';
			$buffer = preg_replace( '~</body(\s+[^>]*)*>~Ui',
				$footer_script . '\\0', $buffer, 1 );
		} else {   // 'sync_head'
			$head_script =
				'<style>img.lazy{min-height:1px}</style>' .
				'<script src="' . esc_url( $js_url ) . '"></script>';
			$buffer = preg_replace( '~<head(\s+[^>]*)*>~Ui',
				'\\0' . $head_script, $buffer, 1 );

			$footer_script =
				'<script>' .
					'window.w3tc_lazyload=new LazyLoad(' . $config . ');' .
					$on_initialized_javascript .
				'</script>';
			$buffer = preg_replace( '~</body(\s+[^>]*)*>~Ui',
				$footer_script . '\\0', $buffer, 1 );
		}

		return $buffer;
	}



	public function wp_get_attachment_url( $url, $post_id ) {
		$this->posts_by_url[$url] = $post_id;
		return $url;
	}



	private function metaslider_hooks() {
		add_filter( 'metaslider_nivo_slider_get_html',
			array( $this, 'metaslider_nivo_slider_get_html' ) );
	}



	public function metaslider_nivo_slider_get_html( $content ) {
		// nivo slider use "src" attr of <img> tags to populate
		// own image via JS, i.e. cant be replaced by lazyloading
		$content = preg_replace(
			'~(\s+)(class=)([\"\'])(.*?)([\"\'])~',
			'$1$2$3$4 no-lazy$5', $content
		);

		return $content;
	}
}