[ZPT] Stylesheet Language

[Paul Everitt]

I thought this idea was groovy back during Casey's IPC talk, and I still 
think it's groovy.  Couple of points:

1) Obviously it gives an option for people that *really* want further 
separation of presentation and logic.  The Dreamweaver jockeys and the 
Zope jockeys don't even work on the same file/object (if you can use a 
<link> that gets rendered server-side).

2) As noted here, you can do something that's painful in current ZPT: in 
one fell swoop, apply logic to many elements using a selector-style 
approach.

3) If you later chose to, you can do interesting things with things with 
the under-appreciated areas of CSS, such as pseudo selectors.

4) You can alter the idea of macros by programmatically deciding which 
of several <link>'d TSSLs to apply to a document.

5) For a bizarre twist on (4), you could have multiple "pipelined" TSSL 
stylesheets, with the output of one being the input of the next.  OK, 
that's too bizarre, I retract it. :)

--Paul

Evan Simpson wrote:
> Thanks to Casey Duncan, I'm now thinking hard about an extension to ZPT 
> that I'm tentatively calling Template Style Sheet Language (pronounced 
> "Tassle").  Much like CSS, this would allow you to write the equivalent 
> of TAL statements out-of-line, and apply them based on tag selectors.
> 
> Stylesheet sytax is much more forgiving than attribute syntax, so some 
> of the more awkward aspects of TAL could be abandoned.  For instance, we 
> can use "=" instead of "define", and we can have multiple instances of 
> the same kind of statement applied in whatever order we specify.  String 
> expressions could simply be quoted strings, and explicit expression 
> types could become pseudo-functions such as "python(<expr>)". A major 
> advantage would be the ability to attach generic code to tags based on 
> pattern matching.  This also eliminates the need to add new tags in 
> order to control scope and order of operations.
> 
> Here's a complex example with made-up syntax:
> 
> <style type="text/tssl">
>   @begin { base = template/portal_url; }
>   .item-list {
>     items = path-string(attrs/items);
>     @if not(items) replace: structure "<b>No items</b>";
>   }
>   .item-list > * {
>       repeat: item items;
>       i = repeat/item/number;
>       [name] = "item-$1";
>   }
>   img.portal { [src] = "$base/${attrs/src}"; }
>   form.auto {
>     recname = attrs/name;
>     recpath = "$recname | options/$recname | nothing";
>     rec = path_string(recpath);
>   }
>   form.auto input, select, textarea {
>     name = attrs/name;
>     [name] = "$recname.$name:record";
>     value = path_string("rec/$name | nothing");
>   }
>   form.auto input[type=text] {
>     [value] = value;
>   }
>   form.auto textarea {
>     content: value;
>   }
>   form.auto option {
>     optvalue = attrs/value;
>     [selected] = python(value == optvalue);
>   }
> </style>
> 
> <ul class="item-list" items="here/query.sql">
>   <li tal:content="item/text">Record</li>
> </ul>
> 
> <form class="auto" name="person">
>   <img class="portal" src="face.png" />
>   Name: <input type="text" name="fullname" />
>   Password: <input type="password" name="password" />
>   <textarea name="bio"></textarea>
>   Sex: <select name="sex">
>     <option value="M">Male</option>
>     <option value="F">Female</option>
>   </select>
> </form>
> 
> The interaction between TAL and TSSL could be controlled by having all 
> TSSL statements for a tag execute before TAL on the tag, but providing a 
>  "@tal;" statement, so that the following:
> 
> <style type="text/tssl">
> * { x = "1"; @tal; y = "$z 3"; [z] = z; }
> * { y = "2"; @tal; content: y; }
> </style>
> 
> <p tal:define="z string:$x $y"></p>
> 
> ...would produce:
> 
> <p z="1 2">1 2 3</p>
> 
> ...since the order of execution would be:
> 
> 1) x = "1";
> 2) y = "2";
> 3) tal:define="z string:$x $y"
> 4) y = "$z 3";
> 5) [z] = z;
> 6) content: y;
> 
> For documents, such as XML with a DTD, in which an inline <style> would 
> not work, we could (ab)use the standard:
> 
> <?xml-stylesheet path="here/autoform" type="text/tssl"?>
> 
> Cheers,
> 
> Evan @ 4-am
> 
> 
> 
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