[OpenLayers-Dev] projection on geometry
Tim Schaub
tschaub at opengeo.org
Tue Nov 11 16:47:49 EST 2008
Hey-
Picking up on the thread that Bart just referenced:
http://www.mail-archive.com/dev@openlayers.org/msg02523.html
I agree, we should keep track of projection at the geometry level.
There are plenty of times that you have a geometry without a feature or
a layer, and you want to maintain the srs info for that geometry.
I've always thought this change would come with 3.0. But it probably
makes sense to start working it in to see how things go.
Seems to me like we need a setter and getter. So the following would work:
polygon.setProjection(foo);
polygon.components[0].components[0].getProjection(); // foo
And it makes sense to me to push the work on to the setter (setting the
same on all components), making access less work.
I think it also makes sense to me that the layer does not set the
geometry projection. We assume that geometry projection is properly set
before a feature is added to a layer. This pushes the setting or
transforming closer to the parsing (where it makes sense that you'd know
the projection).
In some cases, a format would do the transform (assuming
internal/externalProjection are set). In other cases, a strategy could
do the transform (since it knows the map projection and the layer
projection - where the layer projection should be set to match the source).
I'm sure there's lots more to talk about. This is what a sprint is good
for. Without that, it probably makes sense to get some code going and
see where it takes us. To this end, I've created a new sandbox [1]. I
won't have any time for a bit to work on it, but I'll be happy to comment.
Tim
[1] http://svn.openlayers.org/sandbox/projection
--
Tim Schaub
OpenGeo - http://opengeo.org
Expert service straight from the developers.
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