[whatwg] [html5] Rendering of interactive content

Ian Hickson ian at hixie.ch
Fri Feb 6 10:46:49 PST 2009

On Fri, 6 Feb 2009, Giovanni Campagna wrote:
> I'm proposing to replace the current rendering mechanism, based on 
> Behavioural Extension to CSS, that in turn is based on XBL2, with 
> something based on the CSS3 Basic User Interface (css3-ui), ie replacing 
> the binding: property with appropriate appearance: property directly on 
> the element, instead of relying on the binding itself.

The two properties are orthogonal -- 'binding' sets the behavior, 
'appearance' sets the look-and-feel.

> The advantage of appearance vs binding is that:
> 1) you don't need an additional pass before applying the correct
> platform-specific widget style

With UA-native bindings, you wouldn't need an additional pass either.

> 2) you depend on css3-ui, in CR stage, instead of becss, a very early WD

BECSS is actually probably more stable than CSS3 UI at this point.

> 3) you don't block the binding property: I don't expect that applying an XBL
> binding on an element causes it to appear like a span (because it gets
> almost no default CSS)

This is actually intentional. Experience with elements like <fieldset> 
that have styles that aren't expressed in CSS is that you end up not being 
able to restyle them properly if you desire. With 'binding' we'd be able 
to knock out the whole default rendering (including weird things with the 
children) in one go.

> 4) you keep the appearance property working: current UA (Firefox and Safari
> at least) already implement appearance, and correctly set it on the input
> element. This could no longer be possible using XBL, because of the CSS
> inheritance model inside XBL (if you apply to appearance to some part of the
> shadow tree, it is not visible on the bound element)

I don't understand what you mean here.

> 5) becss requires "one or more binding languages": it is not necessarily 
> XBL2, but currently XBL2 is the only one available: are you constraining 
> the implementation of HTML5 on that of XBL2?

The rendering section has no actual requirements in it, so nothing is 
constrained. Furthermore, nothing requires the binding language used by 
the UA to actually be a real language, so long as it is triggered by the 
'binding' property.

Ian Hickson               U+1047E                )\._.,--....,'``.    fL
http://ln.hixie.ch/       U+263A                /,   _.. \   _\  ;`._ ,.
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