[Tilecache] getLegendGraphic

[Chris Brown]

Hi Chris,

Thanks for the quick thorough response. I hear where you are coming from and
agree with you as in it would simply be a case of updating the static image
each time you update a layer and clear the cache. Sorry I'm not familiar
with Mapnik but would I be right in saying that it's a non-WMS complient
backend?

What you've said has reminded me that TileCache is a caching engine that
caters to more than just WMS so can logically only support a subset of
functionality which is common to each of the supported backends.

When I was thinking of GetLegendGraphic I was thinking of something whereby
the legend graphic is stored in the cache the first time it's loaded from
the WMS, then is reloaded when the cache is cleared, as it the case with
standard tiles, but now understand why this is not in line with the vision
of TileCache.

The use case that I am seeing quite often now is the WMS engine and WMS-C
sitting on the same server and only WMS-C being exposed to the outside
world, which is why I ask if you have you ever thought of doing something
that caters exclusively to WMS, maybe as a separate branch? For me
personally it would be great to see TileCache support all of the features of
WMS. If a feature which is in the specification is not supported by the
backend then the exception from the WMS is just passed onto the client via
TileCache. This way the system isn't catering to the lowest common
denominator in WMS backend implementations.

[Off Topic]

Something else that I've often thought would be useful for a tool like
TileCache that sits between the map server and the client is the
generalization of non-image requests. I would love to use SVG (or even VML)
more on the client but it is often impossible over the web due to the size
of the XML documents for complex shapes. Something that sat in the middle,
performed a generalizing algorithm like the Douglas Peucker and returned the
simplified shape in SVG could open up a whole new world of possibilities in
the world of vector based web mapping. I asked about this on the OSGEO irc,
and it was said that there is something in the pipeline for generalization
but nothing has come of it yet.

Regards,

Chris
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