Re: [pdf-devel] Error module implementation

[jemarch]

   BTW, I read an old mail from Behdad 
   (http://lists.gnu.org/archive/html/pdf-devel/2007-12/msg00059.html) 
   explaining the way errors are propagated in Cairo, using an error state 
   variable within object types. This could be useful (in addition to the 
   current error reporting scheme) if, for example, functions deal with 
   more than one object at the same time (an error could invalidate one of 
   the objects, or both of them, or none). If just an error enum is 
   returned, it is not possible to know which returned objects are valid 
   (unless you specify different return values covering those cases...). 
   The solution would be storing an error state in each object type (which 
   could even be of type pdf_status_t). Did someone elaborate more on this?

The plan is to use `pdf_obj_doc_t' (in the object layer) and
`pdf_doc_t' (in the document layer) to store error states.

The error module will then provide convenient abstractions to
implement these complex error states: stack of errors (status),
etc. We dont need to think about it right now.