docs/pwg/building-filterfactory.xml

<chapter id="chapter-building-filterfactory">
  <title>Creating a Filter with a Filter Factory</title>
    <para>
      A plan for the future is to create a FilterFactory, to make the process of      making a new filter a simple process of specifying a few details, and
      writing a small amount of code to perform the actual data processing.
      Ideally, a FilterFactory would perform the tasks of boilerplate creation,
      code functionality implementation, and filter registration.
    </para>
    <para>
      Unfortunately, this has not yet been implemented. Even when someone
      eventually does write a FilterFactory, this element will not be able to
      cover all the possibilities available for filter writing. Thus, some
      plugins will always need to be manually coded and registered.
    </para>
    <para>
      Here is a rough outline of what is planned: You run the FilterFactory and
      give the factory a list of appropriate function pointers and data
      structures to define a filter. With a reasonable measure of preprocessor
      magic, you just need to provide a name for the filter and definitions of
      the functions and data structures desired. Then you call a macro from
      within plugin_init() that registers the new filter. All the fluff that
      goes into the definition of a filter is thus be hidden from view.
    </para>
</chapter>