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Re: [css3-*] [css3-box] Box Tree terminology for CSS3 specs

From: Tab Atkins Jr. <jackalmage@gmail.com>
Date: Tue, 22 Nov 2011 14:33:40 -0800
Message-ID: <CAAWBYDDmEghToTKn0Gft+Pto3Hovz7TPSGe=6ngcEUc=uDYCNA@mail.gmail.com>
To: fantasai <fantasai.lists@inkedblade.net>
Cc: "www-style@w3.org" <www-style@w3.org>
On Tue, Nov 22, 2011 at 12:31 PM, fantasai
<fantasai.lists@inkedblade.net> wrote:
> So that we can disentangle boxes from elements and logical boxes from box
> pieces in our CSS3 specs, I'm proposing the following terminology (borrowing
> from Rossen's work on css3-break):
>
> element
>  An element in the document tree or a pseudo-element. Elements have
> properties
>  associated with them. An element generates zero or more boxes, but
> typically
>  only one. Of the boxes generated, one of them is the principal box.
> box
>  A box in the box tree. Boxes also have properties associated with them.
> box fragment
>  A piece of a box that has been broken across line/page/column/etc breaks.

This all seems fine at first glance.

> Layout specs should be mostly written in terms of boxes, not elements. If a
> spec
> talks about elements, the editor should be very careful to check that the
> spec
> should indeed be talking about elements, and not about boxes.

I think I agree.

> Tree relationships "child", "sibling", "parent" operate on the box tree,
> not on the element tree, unless otherwise specified (e.g. "child element").
> An out-of-flow box's parent is its in-flow parent, not its containing block.

Yes.

> I also suggest (separately) that the Applies-to: line of a spec describe the
> types of boxes the property applies to rather than the types of elements the
> property applies to. So "All elements" would change to "All box types",
> which
> will mean "all box types except certain pseudo-elements as specified that
> pseudo-element", e.g. ::first-line pseudo-elements and their generated boxes
> do not accept 'height', as stated in the definition of ::first-line. This
> would mean that the Applies-to line would not be applicable to e.g.
> 'display'.

Hm, seems reasonable.
Received on Tuesday, 22 November 2011 22:34:29 GMT

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