RE: [boost] Re: FORMAL Review of "Output Formatter" library - 7 daysleft

From: Reece Dunn (msclrhd_at_[hidden])
Date: 2004-09-17 04:01:07

Jonathan Turkanis wrote:
>"Reece Dunn" <msclrhd_at_[hidden]> wrote in message
>news:BAY24-F288Jecd92bXC000d4659_at_hotmail.com...
> > Although my library is still under review, I am re-architecturing it 
>based
> > on the feedback thus far. This post is the code associated with what was 
>the
> > delimiters/formatters part of the library. They are now given the better
> > name of "decorators".
>
>Hi Reece,
>
>     I'm planning to post a review [ favorable, presumably ;-) ], but 
>haven't
>started to read the thread yet.

Great.

>     I'm sorry I was never able to follow through on my ideas for your 
>library --
>I just got too busy with other things.

No worries.

>If there you feel there are some major
>architectural changes that need to be made, I'm still interested in
>collaborating. My main ideas were a introducing cascading style sheets and
>inline formatters using expression templates.

Formatters are dead! Long live decorators! ;) I am intrigued by the idea of 
cascading style sheets (CSS), but have a question regarding inlined 
formatters/decorators:

What can you do with inlined decorators that you can't do with the 
format/decorate function? For example:

   namespace io = boost::io;
   namespace fmt = boost::io::format;
   std::cout << io::object( ob,
         fmt::container( fmt::pair().decorate( "( ", " )" )).decorate( "[{ 
", " }]" )
      ).decorate( " - " );
      // output: [{ ( a, 5 ), ( b, -1 ) }]

How do you envision CSS working? The way I see it is that you are viewing 
the format objects as HTML tags that have a style attribute associated with 
them that contains a set of ( attribute, value ) pairs (a std::map< 
std::string, std::string >?)

This way, the decorate function would be the equivalent of setting the style 
attribute:
   fmt::pair().decorate( "( ", " )" ); // <pair style = "open: '( '; close: 
' )';"/>

You can also set CSS properties within script code, e.g.
   tag.style.fontFamily = "Times New Roman";

This style behaviour is available in the new decorators, for example:
   io::wrapper_decorators< char > wrap;
   wrap.open = "<< ";
   wrap.close = " >>";

If you save a format object for use later, e.g.:
   fmt::container_t< char, fmt::pair_t< char > > my_fo = fmt::container( 
fmt::pair());

The library should support decorating nested format objects, e.g.:
   my_fo.elem.open = "<< ";
   my_ob.elem.close = " >>";
   my_ob.separator = " | ";

   std::cout << io::object( ob, my_ob ); // output: [ << a, 5 >> | << b, -1 
 >> ]

HTML allows you to associate a stylesheet file with the HTML markup that 
sets how certain tags are displayed, e.g.:
   body{ color: red; }

This will set the font colour of the body element to red. I suppose the 
equivalent here would be the various format objects (each having a "tag" 
name) and the style being saved on a stream. This would allow something 
like:

   std::cout << ( io::css[ "container" ].separator = " : " )
      << io::object( ob ); // output: [ [ a, 5 ] : [ b, -1 ] ]
   std::wcout << ( io::css[ L"pair" ].separator = L" = " )
      << io::object( ob ); // output: [ [ a = 5 ], [ b = -1 ] ]

With the "body{ color: red; }" example, the CSS attribute is inherited to 
all its child tags. The question here would be: should styling be inherited?

Regards,
Reece

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