On Thu, Sep 04, 2025 at 02:34:08PM +0200, Yoav Weiss (@Shopify) wrote:
> Thanks for the description of the issue!
> Is there any way to estimate how many sites will be impacted by the
> slowness here? Do we have a use counter of some sorts? For ones that are
> impacted, how much slower do they become? Are they still usable?

Yes and no. We want to roll this out via Finch, which will at least give us
confidence that it won't have large-scale problems across the web. As for
individual sites, it really depends on a lot of factors; in particular,
how big are the DOMs, how many custom properties does each element have,
how patient is the user? For most cases, the difference is basically zero.
If you have 2000+ custom properties on each element (something that we don't
recommend, but some extreme sites do it nevertheless), you are talking going
from 15 seconds to several minutes. It is still usable, but the user will
probably eventually tire of waiting if the long is long enough.

It is challenging to make an accurate use counter for this. We could have a
counter like “you are accessing custom properties on gCS and you have more
than 500 of them”, but it would have large amounts of false positives.
For instance, this isn't a problem if you also have a small DOM. It's not a
problem if you see them and immediately skip over them instead of cloning
them onto the new element (the recommended patches to html2canvas and
html-to-image do this). Similarly, I suppose “you are using setProperty to
set more than 500 properties on an element” is going to be very imprecise.

This is why we've been using HTTP Archive to try to quantify the impact
manually, however imprecise. And that tells us that while it's common to
include these libraries, actually hitting them in normal use is not that
common, at least in our normal as-a-user experience.

> Would we have some way of pointing the developers of such sites to snapDOM
> or other solutions?

None beyond the bug reports; we've engaged both on the Chromium bug report we
received as well as bug reports in the relevant upstream libraries (including
pdf.js, which is popular and uses html2canvas), and our experience is that
developers have few problems adjusting as long as they know what the fix is.

Of course, they've already had to contend with this slowness for Firefox and
Safari users; some of them may not care, though. But fixing it for M141
will also fix it for users of those browsers.

/* Steinar */
-- 
Homepage: https://www.sesse.net/

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