World: r3wp

That behavior
 = Robert's suggestion

Where are you going to use the IF robert?

view compose/deep [
	button
	(IF condition [button])	
	button
]

>> condition: false
== false
>> probe compose/deep [ button (if condition [button]) button ]
[button none button]
== [button none button]

>> compose/deep [ button (either false [[button]] [()]) button ]
== [button button]

Yes, and this none could be skipped by the layout parser.

yes, that's what I'm asking for .. a no-op

I wanted to have this implicit NONE skipping for a long time. I'm 
not a fan of  using an either just to return "nothing". IMO an if 
that doesn't return anything at all makes a lot of sense if used 
with COMPOSE.

if no-op is served by none, then fine

I misunderstood your suggestion, Robert. I thought you were talking 
about adding an IF command to the layout dialect, not to the code 
in the ().

Robert, this implicit none is not possible ...with Rebol

We discussed this recently

Brian, no that was the idea.

but since none can be used sometimes for part of the layout I thought 
it would be easier to parse if we used something else

The IF command in the dialect would get rid of the COMPOSE and do 
this: view [button if (condition) button button]

That is what I meant by a Parse-like IF. Possibly not doable in the 
layout dialect, due to overhead.

Putting the IF in the paren and using COMPOSE would be something 
different.

I don't see why.... it just adds more clutter to the dialect

I'd vote against that idea

Like I said, too much overhead. But that is what I thought Robert 
was suggesting (until he demonstrated otherwise).

unless we start adding conditions to the whole vid dialect ...

That would be the suggestion, yes.

I don't like it though. It you add conditions to the dialect it will 
make it too easy to put semantic code into a layout that is just 
supposed to be for display.

In fact why don't we consider using parens to switch out of the layout 
dialect instead of making us use compose'deep

nah... too complicated

Again, there should be no DO dialect code in the layout dialect. 
Unless actions are called, the layout dialect should be declarative, 
not procedural. That is what makes it safe.

we already have a do in the vid dialect

It's a DO action. The code in its argument only gets called as a 
result of the action, not at layout time.

view layout [
	button 
	do [ this at layout time [
]

That code doesn't make sense, even with the missing ]. Are you thinking 
VID or the R3 GUI?

Oh, you meant do [ this at layout time ]. It doesn't do it at layout 
time, only when the button is clicked.

The DO [ ... ] is an action modifier to the button declaration.

Brian, I take it you have never done any Vid work ?

Very little. Most of my VID knowledge comes from DevBase 2 and the 
VID resize project. Aside from that, very little GUI work in REBOL, 
just (many) other languages. Most of my REBOL code has a web or batch 
UI, or no UI at all.

I had to learn a lot of VID's internals to do the resize project. 
But I don't really need to make GUIs much.

the dialect word 'do switches the layout parser to the do dialect

for VID1, 2, and 3 ( I think )

Likely not in the R3 GUI. We did a lot of work to separate layout 
and behavior.

likely you mean

Not unless it has been changed recently. According to the design 
of the R3 GUI, DO doesn't switch the layout dialect into DO dialect 
mode, it declares an action for the button (in your example) to perform 
when clicked.

The code performed by that action is evaluated by the DO dialect, 
but it is evaluated at runtime in response to the action being triggered, 
not at layout time.

My example is for R2 ...  there is no 'layout word for R3

Ah, wrong group then. The layout dialect is implicit in R3's VIEW 
function now, not implemented by a separate LAYOUT function.

What does this do ?

view layout [ button "test Brian" do [print now ]]

As for R3 is supposed to do .. has anyone read the specs??

I helped design the specs (mostly in an advisory capacity).

Does this still apply to the WIP ? http://www.rebol.com/r3/docs/gui/gui.html

Get rid of the call to LAYOUT, and it will create and show a layout 
with a button titled "test Brian". When that button is clicked, the 
button's action will be triggered, and the result of NOW will be 
printed to the console.

What does it do in VID2 ?

There are some changes since the docs there were written, but the 
overall design model is the same. At the moment, groups and panels 
work differently than those docs.

In VID2, it seems to print now before the button is clicked.