Implementation

Support for a new type of document writer requires a new structure, derived from fz_document_writer:

$\begin{lstlisting} typedef struct { fz_document_writer_begin_page_fn *begin_pag... ..._writer_fn *drop_writer; fz_device *dev; } fz_document_writer; \end{lstlisting}$

For instance:

$\begin{lstlisting} typedef struct { fz_document_writer super; <foo specific fields> } foo_document_writer; \end{lstlisting}$

A generator function should be defined to return such an instance, perhaps:

$\begin{lstlisting} fz_document_writer *fz_new_foo_document_writer(fz_context *ct... ...par <initialise foo specific fields> \par return &foo->super; } \end{lstlisting}$

This uses a friendly macro that allocates a structure of the required size, initialises the function pointers as required, and zeroes the extra values in the structure.

$\begin{lstlisting} /* fz_new_document_writer_of_size: Internal function to allo... ...f_size(CTX,sizeof(TYPE),BEGIN_PAGE,END_PAGE,CLOSE,DROP), ...$

The actual work for the document writer is done in the functions that are passed to fz_new_derived_document_writer. In the example above these were foo_begin_page, foo_end_page, foo_close, and foo_drop. These have the following 4 types respectively.

$\begin{lstlisting} /* fz_document_writer_begin_page_fn: Function type to start ... ...iter_drop_writer_fn)(fz_context *ctx, fz_document_writer *wri); \end{lstlisting}$

Once defined, if this is intended to be a generally useful document writer, it should probably be hooked into fz_new_document_writer, where it can be selected by appropriate format and options strings.