[Grok-dev] Re: Skinning/themeing

Martijn Faassen faassen at startifact.com
Fri May 18 18:37:08 EDT 2007

Martin Aspeli wrote:
> Lennart Regebro wrote:
>> Sure:
>> http://mail.zope.org/pipermail/grok-dev/2007-March/000476.html
> I see! This looks very powerful and cool.
> I assume we are still considering viewlets as the way of making 
> "pluggable" UIs, i.e. aspects of a page where you can plug in new 
> elements without modifying the view, and where you can vary the thing
>  being plugged in by context type.
> Or are we thinking this is the general approach to page composition?

I admit that though I've seen them in use in Schooltool (and being put 
off by the tremdendous amount of ZCML they seemed to need) and after 
having listened to Philipp's talk about them at last year's DZUG 
conference, I still don't grok them. Philipp's talk was fine, I think 
that's because I haven't actually tried to use them myself yet, so they 
don't stick in my brain.

So my answer to this: I don't know. :) I'm hoping Lennart has a better

> Also I'm not convinced that it solves the general themeing/branding
> problem. The premise of Deliverance (or something like it) is that
> the designer (be he the same or a different person to the one doing
> the compositing and the raw development) makes a full, flat, static
> HTML page (or pages) which defines "the way it should look", and then
> pulls the relevant parts of the "composed" page into the correct
> parts that static page. That allows them to use familiar tools (e.g.
> Dreamweaver) and design a "whole" into which the application slots

> The match approach described in the email above, as I understand it,
> is about defining a pipeline which post-processes the "bits" of a
> page (which is of course useful for all kinds of things). It works
> the opposite way to Deliverance, in that you start with a "composed"
> set of markup and then selectively swap out bits of it. I can't see
> how someone wearing ad designer hat would make lots of these little
> match classes and template snippets to theme a page.

Actually there are two places to use xpath with MatchViews. One place is
to match with part of a page. That could be a part of a page, but note
it could also be the whole page.

Then the second place where you can use xpath is to pull in bits of the 
matched HTML.

So, you could set up a match view that matches with the whole page. The
template would be a fully themed page. It would pull in bits of the
original page using xpath.

I think that this means we could do what you describe Deliverance does. 
Hopefully we also allow the user to still access the original context 
object somehow, to get information from it the python-way. This breaks a 
pure pipeline model (which has definite advantages) but the gain in 
expressive power may be worth it.

We have many details to work out, such as ordering issues. Which 
MatchViews get applied first? What if you have a whole-page MatchView 
and then also ones that match smaller bits?

I'm not guaranteeing any of this will actually work in practice. :) One 
thing we should definitely do is to make a careful study of Deliverance 
before we start implementing this. I also need to get a better picture 
of how viewlets fit into all of this.



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