MS RFC: Layer Plug-in Architecture

[Jani Averbach]

> -----Original Message-----
> Tamas Szekeres wrote on Friday, September 09, 2005 3:10 PM

Hello Tamas,
 
> Could you point me to a working sample implementation that utilizes
> the concept of this proposal in order to review the possibilities of
> mapping with SWIG C#.

There isn't anything working which is strictly based on this
RFC. However, I posted to the MapServer-dev a prototype patch which
implemented plug-in architecture for MapServer. The message was:

Message-Id: <smtpd.489f.4303bde2.8dbaf.f at mtaout-w.tc.umn.edu>
Date:         Wed, 17 Aug 2005 16:44:44 -0600
Subject: Mapserver Plug-in Infastructure: RFC and PATCH

 
> It seems this solution requires a run time cast on the vtable at the
> client side, but I couldn't see how to enforce the client to use the
> proper fn signature depending on the type of the layer. Is the
> vtable layout static for a particular type?

The main idea is that the vtable is a private data for layer, so you
are not supposed to call any layer functions by yourself by vtable.
Instead you should use existing layer functions e.g..  'msLayerIsOpen',
'msLayerWhichShapes' and so on. What happens internally is that these
calls are multiplexed by vtable instead of static switch.

Also the vtable layout is static for all layers, so all layers will
share same vtable structure layout and the vtable function signatures 
will be same for all layers.  This vtable interface is an abstraction 
layer how MapServer sees all layers and their common operations.

I hope that this clarified things.

BR, Jani

-- 
Jani Averbach