Screenshots don't match with first meaningful paint

Provide the steps to reproduce

Vist https://jantimon.github.io/css-framework-performance/ or

git clone https://github.com/jantimon/css-framework-performance
cd css-framework-performance
npm i
npm run reports

Internally it executes the following command:

  lighthouse
    http://127.0.0.1/
    --throttling.cpuSlowdownMultiplier=4
    --chrome-flags="--headless"

What is the current behavior?

For the default throttling settings the screenshot and the first meaningful paint don’t match at all:

The screenshots are all the same inside “screenshot-thumbnails”.

https://github.com/jantimon/css-framework-performance/blob/49e86ee318bb90070f3d80aa711836efa2f92f51/reports/4g/vanilla/index-0.report.json#L110

Full report as html:

https://github.com/jantimon/css-framework-performance/blob/49e86ee318bb90070f3d80aa711836efa2f92f51/reports/4g/vanilla/index-0.report.html

What is the expected behavior?

first meaningful paint should match screenshots like in this example (the first meaning full paint is 1.3s and the screenshot thubmnails show it around the same time):

To generate the second image I added --throttling-method=devtools

Environment Information

• Affected Channels: “@lhci/cli”: “0.3.12”,
• Lighthouse version: 5.5.0
• Chrome version: HeadlessChrome/80.0.3987.149
• Operating System: ubuntu-18.04

[jantimon]

OH sorry now I get it.

It looks like it works perfectly with --throttling-method=devtools…
I just got confused because the numbers in the report didn’t match with the docs https://github.com/GoogleChrome/lighthouse/blob/master/docs/throttling.md

But that’s only because of https://github.com/GoogleChrome/lighthouse/blob/ac186d0ecbdce739961b7be086dc8f3dbf86f4fa/lighthouse-core/config/constants.js#L8-L15

[jantimon]

Thank you so much for taking so much time for this.
I will close this issue 😃