Tracking script causes forced reflow of the page

[mquandalle]

Past Issues Searched

• I have searched open and closed issues to make sure that the bug has not yet been reported

Issue is a Bug Report

• This is a bug report and not a feature request, nor asking for self-hosted support

Using official Plausible Cloud hosting or self-hosting?

Plausible Cloud from plausible.io

Describe the bug

I noticed the following performance issue in Google PageSpeed insights for my site: https://pagespeed.web.dev/analysis/https-bonforfait-fr-forfait-mobile/cb3p4e98kp?utm_source=search_console&form_factor=mobile&hl=en

This is caused by the the Plausible tracking script:

analytics/tracker/src/engagement.js

Lines 129 to 136 in 1531386

	return Math.max(
	body.scrollHeight || 0,
	body.offsetHeight || 0,
	body.clientHeight || 0,
	el.scrollHeight || 0,
	el.offsetHeight || 0,
	el.clientHeight || 0
	)

This code is used in the getDocumentHeight function to track scrolling position.

Expected behavior

I'd like to avoid performance this penalty.

Maybe it is possible to wrap the getDocumentHeight function in a requestAnimationFrame? And to cache its value?

An alternative would be having the option to disable scroll tracking.

Screenshots

No response

Environment