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Re: Taking a look at overflow: pan

From: Bert Bos <bert@w3.org>
Date: Wed, 4 Aug 2010 19:30:35 +0200
To: www-style@w3.org
Message-Id: <201008041930.35333.bert@w3.org>
On Thursday 29 July 2010 22:24:20 Charles Pritchard wrote:
> This is a cross-post original sent to the whatwg mailing list.
> Style is a more appropriate section for it.
> I'm suggesting an additional attribute usable with the overflow
> property, suggesting that the UI allow the user to "pan" hidden
> content, falling back on scroll bars.
> "overflow: scroll pan;" could allow user agents to display a window
> with additional content, without necessarily showing traditional
> scroll bars.

Different devices and different kinds of user agents have different ways 
of scrolling. Therefore, when we had to, because of mobile phones, we 
introduced 'overflow-style' as a separate property from 'overflow' in 
the Marquee module (http://www.w3.org/TR/css3-marquee/).

We wanted that user agents implemented the 'overflow' property, but were 
free to implement 'overflow-style' or not. Only user agents that need 
to conform to the Mobile profile have to implement 'overflow-style', 
because traditionally designers have been able to select the "marquee" 
effect as a way of scrolling on mobile phones.

Apart from marquee and a panner, there are many other types of 
scrolling: the panner could be in a specific corner and be permanent or 
only appear when the mouse hovers; there could be no panner at all, but 
just a mouse cursor that changes into a hand for dragging the element 
around; there could be scrollbars on the left and top instead of the 
right and bottom edge; there could be a "dog ear" in the corner to flip 
to the next pageful; there could be arrows that appear near the edges 
and that you can click on; there could be a zoom effect, to make the 
element smaller, such as with the two-fingers gestures on some touch 
screens; there could be the scroll method as in Quicktime VR, where 
dragging the mouse a short distance causes the element to move in that 
directions with a speed proportional to the distance the mouse has 
moved; one program I have also allows scrolling by zooming out around 
one point and then zooming in around another...

I don't think we should restrict the interaction between user agents and 
users. And, as a user, I wouldn't want inconsistency between documents; 
only inconsistency between browsers, because then I can choose the 
browser that I like best...

> Original message below.
> ....
> Hey all,
> I've been working on a project which implements tiled scrolling...
> Today from Ajaxian I saw the YUI 3 update, included in it is an
> implementation
> of ScrollView.
> ScrollView is in some sense: overflow: pan;
> It's similar to overflow: scroll, but instead of showing scroll bars,
> it allows
> the user to pan across the element, showing scroll indicators.
> This causes some implementation difficulties when it comes to text
> selection.
> Android, iOS (Apple) and YUI are supporting this style of
> overflow/scrolling.
> SVG and other vector based viewers have often had panning options.
> YUI shows, pretty clearly, how an element like "overflow: pan;" would
> work in typical web-based content.
> Here's their example (admittedly, with turbulence) :
> http://yuiblog.com/sandbox/yui/3.2.0pr1/examples/scrollview/index.htm
> It's a thought. I've worked hard to on my naming schemes, to match
> them with standards where I can. The ScrollView is just a one-off
> from what we're already dealing with
> with overflow: scroll.

  Bert Bos                                ( W 3 C ) http://www.w3.org/
  http://www.w3.org/people/bos                               W3C/ERCIM
  bert@w3.org                             2004 Rt des Lucioles / BP 93
  +33 (0)4 92 38 76 92            06902 Sophia Antipolis Cedex, France
Received on Wednesday, 4 August 2010 17:31:04 UTC

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