[Dev-luatex] attributes

[Hans Hagen]

Chris Rowley wrote:
> Taco wrote --
>
>   
>> When replying, please edit your Subject line so it is more specific
>> Hans and I are working on a new feature we call "attributes".
>>     
>
> Sounds like the idea we talked about in ... somewhere ...??
>   
dunno, the name attribute is rather generic -)
> So is this an arbitrary dictionary (list of name, value pairs?
>
>   
no, currently just an array of numbers attached to each node, the index 
in the attribute

attr 1, value 10
attr 5, value 32

so, when attr 5 deals with color, teh value 10 can represent a specific 
color; eventually this will result in a pdfliteral or special to be 
inserted but that's up to the user (macro writer); such insertion can 
take place for instance at shipout time by manipulating the final node 
list (then typeset content)
>> An attribute is an item that becomes attached to the actual nodes
>> that are to be typeset.
>>     
>
> But what is a `node to be typeset'?  Or is this deliberately vague?
>   
the node lists at each stage ... after boxing, before line breaking, 
what enters the output routine (linebreaking done then);
> Anything in an hlist or vlist?  Or only character(/glyph??) nodes?
>   
anything ... glyphs, glue, penalty, whatsits, h/vlists ...

luatex only provides generic mechanisms are provided, (i.e. opens up the 
engine and adds a few features that we think that should be there); one 
can use attributes to implement for instance color, but the actual 
implementation is up to the macro package writer (ok, i will probably 
provide some generic code, but even then, the interfaces on top of that 
may differ)

Hans


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