[rosser]

This specific problem is one of those exceptions.

This is a known issue, and has been around since at least v57. There are multiple Bugzilla issues on it. The cause is known. It isn't extensions. The fix is just invasive, and apparently ongoing.

[acdha]

That’s true but not what this thread was about. The person I responded to above was making a very broad claim, which is wrong, and jillesvangurp agreed with the observation and added a general point which is correct. There is a specific issue affecting a subset of people with less common configurations but that doesn’t make the sweeping claim true or the recognition that browser performance issues are notoriously poorly attributed untrue.

[rosser]

No, it's specifically what this thread is about.

The thread-parent absolutely cast a wider net than warranted, but everyone in this discussion who has experienced this problem knows exactly which one we're talking about, and the rest are all, "I've never seen a problem!" or "It's probably just extensions." Meanwhile, there's reliably a sub-thread somewhere in the discussion on nearly every article about Firefox, about this problem.

I find it profoundly ironic that you comment down-thread that "humans are very prone to confusing things which affect them personally with the general case" about a thing which you haven't personally experienced. You talk as if those of us for whom this is a 100% reproducible problem are an edge case, based AFAICT solely on your own not suffering it, coupled with your (not incorrect) beliefs about people poorly attributing performance problems in general.

That juxtaposition is really galling.

[acdha]

I was aware of the issue already but that’s also why I knew that the biggest impact comes from a non-default setting. I never said that it wasn’t a real problem, or that it doesn’t warrant attention — only that it wasn’t as broad as claimed and that is a very common problem with browser issues because everyone uses them but people who don’t have problems generally don’t go around posting that everything is fine whereas the percentage of users who are affected will complain regularly.

[aeonsky]

Scaled resolution option is so widely used that it might as well be broken entirely.

[acdha]

Do you have data supporting that claim?

[aeonsky]

Do you require a scientific study for any fact? If you bothered to do any googling, or whatever Mozilla equivalent of google is - this is in the top 3 results. https://9to5mac.com/2016/12/02/15-inch-macbook-pro-screen-re... Scaled resolution is defaulted on a huge amount of Macs.

[acdha]

I asked for data because humans are very prone to confusing things which affect them personally with the general case. Since Mozilla uses telemetry heavily I tend to trust their prioritization more than random self-selected commenters.