We do not as a rule cache
any features - in part so we can work
with massive content.
As a framework we want to be as
light on resources as possible, and
leave it up to applications that use
uDig to choose when (and what) to
cache.
There is a cache checkbox in the
style editor you can tick as an
experimental option, it keeps the
features in a spatial index (and pull
features in as needed as your scroll
around. It is very effective when
working with things like WFS.
The second question is a bit more
interesting, wanting features in world
coordinates.
If you want to do that make a
request of the feature source and fill
in the viewport CRS in the Query
object. The features will be
reprojected as they come out of the
database or shapefile. Indeed in some
cases the data sources supports native
reproduction allowing us to do less
work in uDig.
Note that the features that are
drawn on screen are subject to
"decimation" by the rendering engine,
we throw out coordinates on the fly,
based on the math transform
constructed between the original data,
the world CRS and the affine
transformation to the screen. The
earlier we can throw out coordinates
the less information involved in
drawing, and the faster we can update
the screen.
Jody
