If Fwt can work like HTML+CSS+JS that will be interesting:

//content
root := Pane
{
  Button{ id = "ok"; style = "form"; text = "OK" },
}

//style
root.select(".form") { it.background = Color.red }

//logic
root.findById("ok").onAction.add
{
  ...
}

Definitely an interesting idea. I think we would tone it down and simplify for FWT - but could be quite useful.

Interesting idea reminds me of Ted Nelson's idea about three separate levels:

* A content layer to facilitate editing, content linking, and
  transclusion management.
* A structure layer, declarable separately. 
  Users should be able to specify entities,
  connectionsand co-presence logic, defined independently
  of appearance or size or contents; as well as 
  overlay correspondence, links, transclusions,
  and "hoses" for movable content.
* A special-effects-and-primping layer should
  allow the declaration of ever-so-many fonts, format
  blocks, fanfares, and whizbangs, and their assignment 
  to what's in the content and structure layers.

For Fantom I see this better suited as some kind of FanDom web server or something. As for syntaxI'd prefer:

//content
root := Pane 
{
   Button{ text= "OK" data= ".form"},
}

//style
StyleDSL<| Pane>Button[text="OK"] { background = red} 
           ".form" {background = red} //does same as line above
         |>

//logic
findFirst.bind(ADD)
{
...
}

I think the real value here is "selection" - via some form of classes and/or ids. Today you generally have to keep fields pointing to all the widgets you plan to interact with. So I see alot of value in being able to query into a widget tree.

Getting into all the styling aspects is a bit thorny - and would be difficult to make cross platform I think. The approach I used in webfwt is to extend certain widgets and expose overriding styling and/or adding CSS directly - since its designed explicitly to only run in web browsers.

That design worked really well - and we were able to use alot of cools stuff like box-shadow, border-radius, and CSS transitions, since we didn't need to worry about making it work cross-platform.