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Re: scroll bar size in width calculations

From: David Woolley <forums@david-woolley.me.uk>
Date: Sun, 06 Jan 2008 10:54:38 +0000
Message-ID: <4780B36E.1080204@david-woolley.me.uk>
To: CSS Style <www-style@w3.org>

Brad Kemper wrote:
> 
> In some browsers the horizontal scroll bar appears whenever the vertical 
> one does, but this seems wrong to me. With overflow:auto, there is 
> supposed to be "a scrolling mechanism to be provided for overflowing 

I believe that "mechanism" is used here because the intent is that 
mechanisms other than scroll bars, in particular pointer dragging, as 
used in Google maps and Acrobat, will also fulfill the requirement.

> *auto*
> The behavior of the 'auto' value is user agent-dependent, but should 
> cause a horizontal scrolling mechanism to be provided for horizontally 
> overflowing boxes, and  should cause a vertical scrolling mechanism to 
> be provided for vertical overflowing boxes.

Given that you cannot even rely on any widget being provided, I think 
that a scroll bar with no possibility of scrolling would fulfill this 
requirement!  I think, if you want to have specific rules for 
scrollbars, you will need to define scrollbars, and then say, "if the 
mechanism used is scrollbars....". You might be able to abstract more by 
referring to mechanisms that have separate horizontal and vertical 
elements that are actually displayed, although I think it might be going 
to extremes to require a four arrow cursor to reduce to a two arrow one.

> 
> I usually resort to "overflow-x: hidden;" so that I can get consistent 
> results, predictable content heights, and no useless UI elements taking 
> up space when they are not needed. 
> 

Note that forcing scrollbars in a user agent that normally only uses 
dragging is not good for usability.  (I will let Google Maps off, 
because the zoom range and the finite unbounded nature of horizontal 
movement on a Mercator projection aren't really compatible with scroll 
bars.)

-- 
David Woolley
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Received on Sunday, 6 January 2008 10:55:12 GMT

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