W3C home > Mailing lists > Public > www-style@w3.org > April 2015

Re: [cssom-view] Easing the transition to spec-compatible body scrollTop behavior

From: Rick Byers <rbyers@chromium.org>
Date: Mon, 13 Apr 2015 17:16:12 -0400
Message-ID: <CAFUtAY_vKEebiUchNqdLOkoS9U9OZmaJD9eh5VyRbOMoXvYDCA@mail.gmail.com>
To: Simon Pieters <simonp@opera.com>
Cc: "Robert O'Callahan" <robert@ocallahan.org>, "www-style@w3.org" <www-style@w3.org>
On Mon, Apr 13, 2015 at 5:13 PM, Simon Pieters <simonp@opera.com> wrote:

> On Mon, 13 Apr 2015 21:20:42 +0200, Rick Byers <rbyers@chromium.org>
> wrote:
>
>  What do you think the behavior should be for a document in quirks mode
>>> when the body element has an associated scrolling box?  In that case
>>> there
>>> is really NO viewport scrolling element (setting body.scrollTop changes
>>> the
>>> body element's scroll position, and documentElement.scrollTop is defined
>>> to
>>> be always 0).
>>>
>>> Your current wording says document.scrollingElement should be 'body' in
>>> this case, but null feels more logical (and slightly simplifies
>>> implementation and probably the ultimate spec wording of scrollTop etc.).
>>> However it might be more convenient for libraries that want to assume
>>> there's some scrollingElement if we returned body in this case.  WDYT?
>>>
>>>
>> Ping.
>>
>> I'm implementing this case as 'null' in blink at the moment (but won't
>> ship
>> it until we reach consensus here of course).  It really does seem to make
>> the most sense to me.  I believe it allows the spec text (and therefore
>> implementation) of all the other Element scrolling APIs to be strictly of
>> the form:  "If this == document.scrollingElement then operate on the
>> viewport else operate on this".  Also returning null in this case is the
>> only way to guarantee that
>> document.scrollingElement.scrollTop===window.scrollY (either true or
>> throws).
>>
>
> Yeah, it should be null to match scrollTop's behavior. This was an
> oversight.
>
> https://github.com/w3c/csswg-drafts/commit/ad098d66cfc02a4952e8af2eeea742
> c520d10c2b


Perfect, thanks!


> --
> Simon Pieters
> Opera Software
>
Received on Monday, 13 April 2015 21:17:00 UTC

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