[NTG-pdftex] Synchronization

Taco Hoekwater taco at elvenkind.com
Sat Feb 9 09:43:59 CET 2008

Hi Jérôme,

LAURENS Jérôme wrote:
>> * how does this patch relate to the --src-specials switch from web2c,
> No common code
> better design
> stronger design
> better result

Does that mean that eventually we may get rid of --src-specials
completely? (That would be good). Right now, we will probably have
both at the same time and I was a little worried that they might
interfere with eachother. From you long explanation below, I now
understand that they don't.

>> and what editor/previewer combinations understand your files format?
>> (and/or are likely to start doing that in the future)
> I understand your question: you are wondering if this feature would be  
> used by a viewer or an editor.
> Anyone who ever used synchronization does not ask this question  
> because he knows that such a synchronization is a "must have".

Thanks for the long technical answer as well. So far, I have never
really used editor synchronization tools in my TeX work. Personally,
I always found that the semi-automatic window changes were very
distracting. I have never been much of a fan of integrated TeX systems
either, for much the same reason (this is a matter of personal taste,
so don't take it as a critique on your patch).

>> This will result in more lines of web changes, but it will be easier
>> to maintain the code by someone that is not you.
> If you are talking about code design, I would follow you if you could  
> explain what kind of extensions you are thinking of.

You made a convincing argument, so just leave it as is.

To give you an idea of what I am talking about, here is the list of
nodes that have size>3 already even without your patch in luatex
(you could consider luatex an extension to pdftex):

Core output nodes:       disc, box, rule, glyph, margin_kern

Whatits that are output: pdf_refxform, pdf_refximage,
                          pdf_annot, pdf_dest, pdf_thread,

Internal stream nodes:   ins_node, page_ins_node

Internal whatsits:       dir, open, local_par, pdf_colorstack,

Temporary math objects:  style, radical_noad, accent_noad,
(about everything)       fraction_noad, noad

Alignment stack entries: align_stack

Paragraph breaking:      hyphenated, unhyphenated, passive, delta

Weird ones:              shape, pseudo_line
(variable size)

Some of those are candidates for synchronization, but many are not.
A whole bunch of them is never written to the output at all.

Like I said, leave your code as is. But I want to show you how
it would also have been possible (luatex pascal web, not pdftex,
but it does not really matter):

   @d box_node_size=8+synchronization_field_size
      {number of words to allocate for a box node}
   @p function new_null_box:pointer; {creates a new box node}
   var p:pointer; {the new node}
   begin p:=new_node(hlist_node,min_quarterword);
+ @<Initialize |list_node| synchronization fields@>;
   @p function new_kern(@!w:scaled):pointer;
   var p:pointer; {the new node}
   begin p:=new_node(kern_node,normal);
+ @<Initialize |medium_node| synchronization fields@>;
  ... etc
+ glue_node: begin
+  @<Synchronization dvi hook: output glue info@>;
+  @<Move right or output leaders@>;
+ end;
+ @ All synchronization stuff is handled in this section
+ @d synchronization_field_size==2
+ @<Initialize |list_node| synchronization fields@>=
+ begin
+ mem[p+box_node_size].int := synctag;
+ mem[p+box_node_size+1].int := line;
+ end
+ ....
+ @ @<Synchronization dvi hook: output glue info@>=
+ sync_glue(p);
+ ...

The main advantages:

* a person changing new_null_nox() can immediately see there
   is something going on with synchronization
* all the actual synchronization code is bundled together,
   allowing better documentation
* there may be a bit more code, but less initialization
   instructions are actually executed by the application.

>> * you licensed the C file as GPL2, yes?
> Open source, whether GPL2 or something else, I don't know for sure  
> because I was not given any hint about pdftex development rules.

GPL2 is fine, just making sure.

>> * the attachments seem missing in sarovar.org at the moment
> All the attachments have been removed, there might be a good reason,  
> should I upload once again?

I don't know why they were removed in the first place. Martin,
is that something you did?

Best wishes,

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