Re: API for extension functions (was HTML forms with XSLT slideshow question)

[James Clark <jjc@xxxxxxxxxx>]

Kay Michael wrote:
> 
> > > - how to provide context information (this has been my main reservation
> in
> > > adopting xt's style of interface: it's fine for "pure"
> > functions but doesn't
> > > extend easily to functions that use context, e.g. the
> > current node or the system id of the containing stylesheet node.
> >
> > Why can't you extend it by defining an interface along the lines of:
> >
> > interface XPathContext {
> >   Node getCurrentNode();
> >   String getStylesheetSystemId();
> >   ...
> > }
> >
> > ?
> >
> > Then if the first argument of the Java function is of type
> > XPathContext,
> > the XSLT processor will automatically pass the Java function an
> > additional argument of type XPathContext representing the current
> > context.
> >
> That's certainly one possibility. Another (the one I was planning) is to say
> that if the class containing the extension function implements Contextual,
> then the method setContext(XPathContext) will be called before the function
> itself is called.

That might be OK in a single-threaded environment, but doesn't seem a
good solution in a multi-threaded environment.  It also seems
unsatisfactory for static methods.

Another issue is providing access to information defined by non-XSL
top-level elements (eg an extension function that used top-level
elements in a similar way to format-number() or key()).

James


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