Re: [Groff] grohtml patch

[Gaius Mulley]

Werner LEMBERG <address@hidden> writes:

> > I'm attempting to implement the new tag mechanism that you outlined
> > back in April.  I've implemented the state machine and can issue
> > `diff' tags.
> 
> What exactly do you mean with `diff' tags?

just tags which are only emitted when some aspect of the state
changes.

> > The problem I'm currently struggling with is how to coordinate the
> > updating of the state machine relative to the node generation and
> > final tbuf printing.
> >
> > Currently I'm flushing state machine diffs when the tbuf goes from
> > an empty state into a non empty state. But this is wrong.
> >
> > I'm now considering creating a copy of the troff state machine (my
> > new class based on the list of troff attributes in your email)
> > during env::add_char and adding this copy to a node. Later when this
> > node appears during tprint I am going to diff the nodes state with
> > the driver state and generate the html tags.
> >
> > Can you see anything immediately wrong with this approach?  I'm
> > hoping that it will fix the synchronisation issue..
> 
> Here my idea of implementation:
> 
>   . We need one troff_state structure and a stack of html_state
>     structures.

yes done.

>     Most of the data for the troff state can be directly taken from
>     the `environment' class (or rather, it holds only the stuff not in
>     the `environment' class).

yes, currently it is populated from the environment class and a few
things outside. Whether we have seen an eol, br, or sp and the .ce value.

I had basically reached here (well actually I went further down a
wrong path :-)

>   . We need two new node types, html_state_push and html_state_pop
>     which both must be transparent to end-of-sentence recognition and
>     similar things.
> 
>   . Set a flag diversion::diversion_start in the code for `.di xxx' to
>     indicate that a diversion has just begun.
> 
>     Add an html_state_push node at the very beginning of the diversion
>     to make troff push the html state during rereading.
> 
>   . In env::add_char, test diversion_start of curdiv.  If set, emit
>     the complete troff state as a series of
> 
>       \!\X'html-tag: ...'
> 
>     (or a new special tag which is equivalent to it) right before
>     adding a glyph node.  Then reset the flag.
> 
>     The \! stuff can be directly inserted using a non_interpreted_node
>     structure.
> 
>   . In the code for `.di', add an html_state_pop node at the very end
>     of the diversion to make troff pop the html state during
>     rereading.
> 
> I think you don't need a new node type to hold the troff state since
> its data has been already output as \!'...' stuff.  Since pushing
> and popping the html state is indicated by nodes, implementing a
> proper tprint function for html_state_pop should be sufficient.

yes you're right. Thank you for the clear directions surrounding
diversions, this has cleared my mind considerably..

Gaius