W3C home > Mailing lists > Public > www-style@w3.org > April 2001

Re: opacity in css

From: Chris Lilley <chris@w3.org>
Date: Thu, 19 Apr 2001 03:40:22 +0200
Message-ID: <3ADE4206.6804CD75@w3.org>
To: Tim Bagot <tsb-w3-style-0002@earth.li>
CC: "'www-style@w3.org'" <www-style@w3.org>


Tim Bagot wrote:
> 
> At 2001-04-19T10:11+1000, Brett Donald wrote:-
> 
> > What I was wondering was, whether it makes more sense to merge the proposed
> > 'opacity' property with the existing 'visibility' property. Essentially, the
> > two names are describing the same mechanism, its just that up until now,
> > we've thought of visibility as being only on or off, not a continuum. 

No, this is a very bad idea. Visibility affects whether something gets
pointer events. Opacity is separate.
 
> This is probably more or less true, if and only if the visibility property
> should have no effect on the availability of elements for user
> interaction. 

Exactly.

> Keeping the
> two properties separate might also be more convenient for dynamic effects.

Yes, that is why it was designed that way.

In addition, with fill-opacity and stroke-opacity and semi-opaque
images, having a global opacity property separate from the visibility
property has proven very useful (particularly when used with SMIL
animation of the css properties). 

Plus, it is implemented that way in all the SVG viewers, and the SVG
spec is in CR (actually it has exited CR and is waiting to go to PR) so,
changing the entire way that this all works is highly inadvisable at
this late stage. A lot of thought has gone into the compositing model.
It works well. Lets not go changing it.

-- 
Chris
Received on Wednesday, 18 April 2001 21:41:22 GMT

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