1901780 - www.vanbreda-health.be - The page never fully load

Status: REOPENED

(Web Compatibility :: Site Reports, defect, P3)

Description

[Ksenia Berezina [:ksenia]]

Environment:
Operating system: Windows 10
Firefox version: Firefox 103.0

Steps to reproduce:
Start firefox
enter the URL
wait and wait and wait...

Actual Behavior:
The page/form does not load; firefox hangs

Notes:

• Reproduces regardless of the status of ETP
• Does not reproduce in Firefox Nightly, Firefox Release, and Chrome

Created from https://github.com/webcompat/web-bugs/issues/108406

Comment 1

[Ksenia Berezina [:ksenia]]

From https://github.com/webcompat/web-bugs/issues/108406#issuecomment-1218553265:

This is caused by their site doing this:

//TODO: this is ugly code but fix to make the ugly has-content - stupid way of styling - concept work inside modals.....
$("body").bind("DOMSubtreeModified", function () {
    /* snip some stuff */
    $(".type-address").removeClass("has-content");
    $("select").closest("li").addClass("has-content");
    $(".type-address").removeClass("has-content");
    $(".type-address").find("select").parent().addClass("has-content");
    $(".clear-multi").parent().find("label").addClass("multi-label");
});

And well, they're not wrong that it's ugly. Chrome seems to handle it more gracefully, but mutation events are deprecated for precisely this reason: they perform super poorly (even on Chrome).

I wonder why they felt the need to do this instead of using Mutation Observers instead.. we should reach out to them and find out. I can't even tell from their code why it's needed after it's called once (maybe they can even just remove the listener after the first time it's handled?)

Comment 2

[Ksenia Berezina [:ksenia]]

Diagnosis is already done by Tom. The site has changed and the slowliness only present when selecting radio button options, at least on the page mentioned in the report

Comment 3

[Thomas Wisniewski [:twisniewski]]

Attachment: Bug 1901780 - disable legacy DOM Mutation Events on vanbreda-health.be to fix performance issues; r?ksenia

Comment 4

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/dde74e815a03
disable legacy DOM Mutation Events on vanbreda-health.be to fix performance issues; r=ksenia,webcompat-reviewers

Comment 5

[Sandor Molnar[:smolnar]]

https://hg.mozilla.org/mozilla-central/rev/dde74e815a03

Comment 6

[Thomas Wisniewski [:twisniewski]]

Re-opening, as this is site-patched, not actually fixed.