[Dev-luatex] Hooking into the page builder?

[Graham Douglas]

Taco Hoekwater wrote:
> On 11/22/2010 03:54 PM, Graham Douglas wrote:
>> Hi All
>>
>> I'd like to use GraphViz to create a graph of the entire
>> node structure of a (simple) page. Keeping the page simple
>> and just for experimentation. Not trying to change any values
>> of node lists, just to output values and structures etc.
>>
>> Before I get too far, is it safe/possible to do this?
>> If so, would anyone have some pseudo code I can use to
>> get me started in the right direction...?
>>
>> Many thanks in advance for suggestions etc.
> 
> The simplest is:
> 
> callback.register('pre_output_filter', function (head)
>   ...
>   return head
> end)
> 
> This callback does not replace any code, so you can do whatever you
> want without interfering, as long as you remember to pass back
> 'head'. This callback runs just before box255 is packaged for
> the output routine, btw.
> 
> Best wishes,
> Taco
> 

Many thanks Taco, much appreciated, as always.

Warm regards

Graham