As reported by Jon on https://gerrit.wikimedia.org/r/#/c/152104/

Confirmed FOUC on:

• anon warning
• new-topic content textarea

Both of those have .flow-form-collapsible, which will be hidden/displayed by JS based on the form's data-flow-initial-state. Before that JS is loaded/executed, those elements will be visible (though the default state for all currently is to hide them)

We probably have to tweak that implementation. I'd suggest to have the show/hide in CSS rather than JS, roughly like this:

[data-flow-initial-state=hidden] {
    display: none;
}
[data-flow-initial-state=collapsed] .flow-form-collapsible {
    display: none
}

Rest of the collapse logic can probably stay in JS (I guess.. Other implementations are fine - this is just my initial thought)

Please add to this bug if there are other FOUC that need to be addressed.

Version: unspecified
Severity: normal