[Grok-dev] Re: Skinning/themeing

Fri May 18 20:22:16 EDT 2007

Kevin Smith wrote:

> The work of creating viewlets has been greatly simplified in 
> megrok.quarry (based on Lennart's megrok.viewlet work). For example...
> 
> class MyView(quarry.View):
>     """<html metal:use-macro="context/@@master/page">
>        <body metal:fill-slot="body">
>        <span tal:replace="structure provider:myviewlets" />
>        </body>
>        </html>
>       """
>     template = grok.PageTemplate(__doc__)

Yipes! I realise this is just an example, but the idea of using the 
docstring like that feels very dirty. :)

>     def render(self): pass # trick grok into not requiring 
> app_templates/myview.pt

Also yipes, but I'm sure this could be cleaned up.

> class MyViewlets(quarry.ViewletManager):
>     grok.context(MyView)
>     quarry.name('myviewlets') # provider:myviewlets
> 
> class MyViewlet_10(quarry.Viewlet):
>     grok.viewletmanager(MyViewlets)
> 
>     def render(self):
>         return "GROK SMASH..."

I assume these names are there for ordering? That really strains the 
eyes, though. Why not something like:

class MyFirstViewlet(quarry.Viewlet):
     grok.viewletmanager(MyViewlets)
     quarry.order(10)

     ...

> class MyViewlet_20(quarry.Viewlet):
>     grok.viewletmanager(MyViewlets)
> 
>     def render(self):
>         return "ZCML"
> 
> class MyViewlet_30(quarry.Viewlet): # using inline template
>     """<b>SQL</b>
>     """
>     grok.viewletmanager(MyViewletManager)
>     quarry.template(__doc__)
> 
> class MyViewlet_40(quarry.Viewlet): # using common templates
>     grok.viewletmanager(MyViewlets)
>     quarry.template('myproject.common.boxlayout')
> 
>     def entries(self):
>         return ['PHP', 'ASP', 'RUBY']
> 
> ... add as many viewlets as you need.
> 
> The viewlets are automatically ordered by view name. 

That to me is bad convention-over-configuration. It's fine if names of 
things are used to find related things (view name -> template name). 
Having to artificially constrain names to get the results you want is 
really frustrating though. I *hate* aesthetically un-appealing code. It 
makes me think of Visual Basic for Applications. :-(

> Viewlets are also 
> be more view-l.ike so templates, self.url, self.application_url and the 
> like are all available.

Great!

> In ZPT land, Deliverance and MatchView are orthogonal to viewlets. When 
> used properly, they are a much simpler and powerful mechanism for 
> creating pluggable UI's like Trac uses. If however, Grok were template 
> neutral, I'm not sure what kind of a role *if any* viewlets could play.

FWIW, I think template neutrality is YAGNI, and possibly harmful. It's a 
nice engineering challenge, and it helps enforce separation of concerns 
in code which are probably good practice, but as a user of a framework, 
I want the framework authors to have chosen the template solution for 
me. And I want all documentation and code examples to use the same 
language as well, so that half of it isn't irrelevant to me no matter 
which one I choose. How should I know which one is best for me, anyway, 
if I'm new to the framework?

Martin