On Fri, Mar 29, 2024 at 4:33 AM Noam Rosenthal <nrosent...@chromium.org>
wrote:
>
>
> On Fri, Mar 29, 2024 at 6:33 AM Yoav Weiss (@Shopify) <
> yoavwe...@chromium.org> wrote:
>
>> On top of Domenic's questions, have we tried to estimate the risk here?
>> Even if it's Chromium-only, there could be Enterprise or embedded scenarios
>> that somehow rely on it.
>>
> Yes, and we're willing to keep the old behavior as an enterprise policy,
> at least temporarily.
>
>
>> Do we know how often this blur event actually fires?
>>
>
> There's no way to find out unfortunately. This event is currently fired
> for every removal, and there could be event listeners that handle it, but
> there is no way to tell if functionality builds on it, or at least I
> couldn't think of one (happy for suggestion). We wanted to disable it in a
> finch and If we decide that we would rather leave things as is, staying
> incompatible with Gecko/WebKi/the standard, and also keeping the quirkiness
> of being able to run a script synchronously while a node is removed, I'm
> totally OK with that, but that needs to be a conscious decision.
>
>
>>
>> On Fri, Mar 29, 2024 at 5:28 AM Domenic Denicola <dome...@chromium.org>
>> wrote:
>>
>>>
>>>
>>> On Fri, Mar 29, 2024 at 2:33 AM Noam Rosenthal <nrosent...@chromium.org>
>>> wrote:
>>>
>>>> Contact emailsnrosent...@chromium.org, d...@chromium.org
>>>>
>>>> ExplainerNone
>>>>
>>>
>>> A few paragraphs, including e.g. example code and how it behaves
>>> differently before/after the change, would help clarify this for web
>>> developers.
>>>
>>
> Sure!
> Writing those here, if you think they need to be in some repo that's fine.
> This will mainly affect code that uses global `focus` `blur` event
> listeners to track the active element, for example in a form:
>
> ```js
> form.addEventListener("focus", () => { trackActiveElementChange() }, {
> capture: true});
> form.addEventListener("blur", () => { trackActiveElementChange() },
> {capture: true});
> ```
>
> Now, since the active element might be removed without a `blur` event, the
> same can be achieved with mutation observers:
> ```js
> form.addEventListener("focus", () => { trackActiveElementChange() }, {
> capture: true});
> new MutationObserver(entries => {
> if (Array.from(entries).some(entry => entry.removedNodes.length)
> trackActiveElementChange();
> }).observe(form);
> ```
>
> In essence the author can check that the node either lost focus or was
> removed, but you don't have an event that tells you that "either" happened.
> So all the use cases can be covered, but of course there is a backwards
> compat risk as mentioned in this thread. We should make a decision on how
> to go forward as a balance between the backwards-compat risk and the
> other-browser-compat risk.
>
> This is done as part of an effort to see if we can get rid of (as many as
> possible) scripts that can run in the middle of a DOM operation.
> This one and events on iframe removal are the only ones remaining.
>
To provide a little more context - activeElement tracking is used heavily
by most webapp having non-trivial a11y implementations.
An example of this pattern is something like:
https://github.com/tridactyl/tridactyl/blob/f49e1c94bcd481fdc86fb219335bafc4ce0f25ab/src/content.ts#L180-L187
(From the first page of a github search of activeElement + setInterval).
(Above is for a Firefox specific extension I think - so doesn't have any if
(FIREFOX) for the interval checking).
(Not this case exactly also - but same pattern).
setInterval checking is done for other browsers as there isn't a great way
to check for activeElement changes (maybe there should be async events? -
but thats a separate discussion).
But web developers might have only done the setInterval pattern for
Firefox/Safari.
Ian
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