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Re: [css2][css3-exclusions] 'clip' with more shapes and all elements

From: Robert O'Callahan <robert@ocallahan.org>
Date: Tue, 21 Aug 2012 00:06:11 +1200
Message-ID: <CAOp6jLaXhJMus5gtyY73vO0VjOM5uPDg+RO=P18aOSvCSoFs-w@mail.gmail.com>
To: "Tab Atkins Jr." <jackalmage@gmail.com>
Cc: Dirk Schulze <dschulze@adobe.com>, www-style list <www-style@w3.org>
On Mon, Aug 20, 2012 at 8:13 AM, Tab Atkins Jr. <jackalmage@gmail.com>wrote:

> On Sun, Aug 19, 2012 at 9:42 AM, Dirk Schulze <dschulze@adobe.com> wrote:
> > I wonder if it is possible to extend the 'clip' property to apply to all
> elements (instead of just absolute positioned elements) [1]? FF applies
> 'clip-path'[2] to all elements already. What are the concerns to do so on
> 'clip'?
> >
> > Can we extend 'clip' to use more shapes then just 'rect'? If we get rid
> of these limitations, the 'clip' property would be a lot more useful (or
> maybe useful for the first time? ;) ). The basic shapes 'circle', 'ellipse'
> and 'polygon' (but also 'rectangle') from the exclusion spec [3] seem to be
> good candidates.
> Yes, we can and we should (imo). I'm not sure why 'clip' is restricted
> just to abspos per spec; I assume it's to avoid possible confusion
> because it doesn't change the geometry of the object.

I don't have a good reason to make 'clip' more generally applicable, but
it's possible that copy-paste Web content applies 'clip' to non-abs-pos
content and breaks if you make that work. (For the same reason I'm wary of
making z-index apply to non-positioned elements, even though I'd really
like to.)

> 'clip-path' could still be used for referencing SVG 'clipPath' elements
> or could shadow 'clip' and 'clip' supports a <FuncIRI> as well.
> We've finally stumbled on a decent way to handle aliasing -
> 'clip-path' can be treated as a shorthand for 'clip', and we can add
> url()/select() to 'clip' in addition to the shape functions.

We made clip-path induce a stacking context on the element. As usual, this
made implementation a lot easier.

Making 'clip' handle arbitrary shapes, while not inducing a stacking
context, would be a real pain to implement (although we could do it).
Making 'clip' induce a stacking context would pose its own Web
compatibility hazard.

If some browser vendors wants to do those Web compatibility experiments,
please go ahead. I'm a bit fatigued by break-the-Web experiments at the
moment :-).

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Received on Monday, 20 August 2012 12:06:40 UTC

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