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Re: [css3-transforms] Effect of CSS transforms on scrollable areas

From: Rik Cabanier <cabanier@gmail.com>
Date: Thu, 31 May 2012 20:07:57 +0200
Message-ID: <CAGN7qDCdzexEqZB0paLXJ2daFvUF1y+BkRWvSrunYVE6qxb8ZA@mail.gmail.com>
To: Sebastian Zartner <sebastianzartner@gmx.de>
Cc: robert@ocallahan.org, jackalmage@gmail.com, www-style@w3.org, cjones@mozilla.com
On Thu, May 31, 2012 at 6:52 AM, Sebastian Zartner
<sebastianzartner@gmx.de>wrote:

> > On Thu, May 31, 2012 at 11:31 AM, Robert O'Callahan
> > <robert@ocallahan.org>wrote:
> >
> > > In all major browsers, transforms normally affect the scrollable area
> > > of a scrollable container. However, during an animation or
> > > transition, Webkit treats the transform as having the value it had
> > > the last time it wasn't animated/transitioned:
> > > http://people.mozilla.org/~roc/test_transform_scrollable_area.html
> > > Presumably this is a performance optimization related to asynchronous
> > > compositing.
> > >
> > > I think browsers should behave consistently here. Should we spec the
> > > Webkit behavior? I guess that would be something like
> > > "Transforms affect the scrollable overflow area as expected, unless
> > > they're subject to a CSS animation or transition in which case they
> > > affect the scrollable overflow area as if they had their values from
> > > before they were subject to an animation/transition."
> > >
> >
> > Actually, Webkit's behavior is more complicated than this. Event
> > dispatching can (at least in some cases) cause different behavior.
> >
> > I've updated the testcase. Now if you hover over the animated element
> > while
> > it's animating, you can observe changes to the result of
> > getBoundingClientRect during the animation. Curiously, changes to the
> > scrollbar state are still not reflected until the end of the animation.
> >
> > I don't think we should spec the details of that mess. However, I don't
> > know what to do instead.
>
> I believe what Opera and Firefox do here is what the user would expect.
> Why shouldn't the scrollable area be affected by an animation? Imagine the
> animated object being completely outside of the scrollable container for a
> longer animation and you're not able to scroll to it. Wouldn't that be
> annoying?


What if you want to animate an element in from a side? Wouldn't you think
it's annoying if you get scroll bars while it's not completely on the
screen?
Received on Thursday, 31 May 2012 18:08:27 GMT

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