How to hook WPFC

Hi,

today I’ve noticed a “big problem”. I have to modify the HTML-code after the entire page has been rendered completely. Therefore I’m using a code like this:

function callback($buffer) 	{	return $buffer;	}
function buffer_start() 	{	ob_start("callback");	}
function buffer_end() {

	ob_end_flush();
	$content = ob_get_clean();

	[...do my stuff...]
}
add_action('wp_head', 'buffer_start');
add_action('wp_footer', 'buffer_end');

On the first call of the page everything works fine. But after the first call the WPFC generated cached file is loaded and all my changes are gone.

In other words: WPFC writes the cache file before the page has been finished its rendering. That’s a big problem, because I have to do my code changes at the end of the page generation process – but BEFORE WPFC is writing the cache file.

How can this be done?

Thx for you help!
best regards,
Lars

https://wordpress.org/plugins/wp-fastest-cache/