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Re: [css-transforms] Interaction of transforms with scrollable area

From: Chris Harrelson <chrishtr@google.com>
Date: Wed, 03 Feb 2016 23:20:18 +0000
Message-ID: <CAOMQ+w9LYiOQ3u=DagEKEMqSeV91RqCMnUgy5zCaZsJw0Fur7g@mail.gmail.com>
To: robert@ocallahan.org, www-style <www-style@w3.org>
On Sat, Jan 9, 2016 at 2:30 AM Robert O'Callahan <robert@ocallahan.org>

> Context: https://bugzilla.mozilla.org/show_bug.cgi?id=1236386
> https://bug1236386.bmoattachments.org/attachment.cgi?id=8703469
> This issue's probably already been discussed but I don't know where. The
> question is: how does a transformed element contribute to the scrollable
> area of an "overflow:auto/scroll" ancestor? For example, does its
> border-box before transformation contribute to the scrollable area?
> In the referenced testcase Chrome seems to say "no" if the transformed
> element is a direct child of the box, "yes" otherwise. Firefox says "yes,
> but only in the vertical direction". Edge says "yes". More testing would
> probably be worthwhile.

I dug into the code in Blink to figure out what it's doing, for further
background. The results you see are because of the following implementation

The scrolling area of an overflow-scrolling element is expanded to contain
the transformed size of a *direct* child. It is never contracted if the
transform makes the visual size of the child smaller than its original box.

Here is the WebKit bug <https://bugs.webkit.org/show_bug.cgi?id=47514>
leading to the implementation (It doesn't refer to direct children).


Received on Wednesday, 3 February 2016 23:20:59 UTC

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