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Re: [udig-devel] Layer Selection vs Current Layer 
On Wed, 2006-04-19 at 14:19 +0200, Jody Garnett wrote:
> Adrian Custer wrote:
> > Hey all,
> >
> > I'm a bit lost as well and still sipping the morning brew...
> >
> > As part of my "Geospatial operations" workflow, I imagine the user
> > starts by selecting the "Geospatial data" they want to work with. I
> > imagine this happens by users selecting a Map to work with and
> > subselecting some the elements of the map by choosing:
> >         - 1 or more "Layers" in the "Layers" view (using shift or ctrl
> >         to select several layers).
> >         - 1 or more selection areas on the Map (using bounding boxes
> >         (shift) or more generally a filter of some kind (by hand/gui)).
> > That's the selection I'm about to go after. So far things look broken.
> > The "Selection" view shows all the elements in the top selected layer of
> > the "Layers" view no matter what the "Filter" element says in the
> > "Selection" view. Also, the Filter bounding box only acts on the top
> > layer selected in the "Layers" view for highlighting elements in the
> > "Map" graphical view.
> >
> > So is my intuitive feel for how to select "Geospatial resources" wrong?
> Not at all ... I am afraid I am confusing things because we have three 
> definitions of "selected":

> 1. There is the workbench selection (aka what that article was about)
> - if the layer view is the active part then the workbench selection 
> would consist of 1 or more Layer objects
> - if the Map editor was selected then the workbench selection would 
> depend on what tool you were using, a Feature object would be selected 
> if you were using an edit tool for example
> 
or several features in a single layer if using the "selection" tool,
right?

> 2. There is a Filter associated with each layer (perhaps this should be 
> called "filter" or "indicated")
> - this indicates which features are considered "selected" for rendering 
> (or for any code that wants to check that care about such things)

Does "for rendering" mean "for special consideration when rendering,
such as surrounding them with highlight" rather than "for inclusion in
what is rendered"? Because all the features are rendered, right? This is
not an ON/OFF kind of selection but a "tagged"/"not-tagged" kind of
selection, correct?


> 
> 3. There is the concept of a Map having a "selected" Layer  (perhaps 
> this should be called "current"?)

or possibly "active" in parallel with "active" views?
   AppGIS.getActiveMap().getActiveLayer()?
Although that steps into 'eclipse lingo' which is talking about the GUI
state rather than the data model state.

> - note a map may also have a "selected"  feature selected for those 
> editing tools etc...
how is this different from 1(b)?
> - more generally this can be viewed as anything on the Map blackboard 
> used for collaboration

whatever the blackboard may be. That's in my "to learn" column. :-)




> 
> Sigh I am not even sure if things are always this nice:
> - I suspect you you can ask the currently selected object to "adapt" to 
> something else, so your Feature could be asked to adapt to the Layer it 
> was from ...

Don't sigh! This is hard but good. We need to be very, very clear about
these distinctions.

I'd like to, but don't yet, understand if we *can* create an Eclipse
view that shows us a hiearchy of what's in a Project. This would be a
combination of trees and lists, with some elements being tables. I don't
think I'll know the answer until I come to grips with the work on the
complex features which is going on on its branch. I'm drawing something
like: 

Project
  -----> Map1
  -----> Map2
  -----> Page1
  -----> Map3
          ---> Layeri : Filter
                 ----->Featurem
                           -----> ID
                           -----> Schema
                                     -----> ...
                           -----> defaultGeom
                           -----> attribute
I'm trying to draw this out right now to understand the data model of a
running uDig (and embedded Geotools/jts). I've also been thinking hard
about the spatio-temporal view of features I would like to be working
against. Finally, I suspect the same kind of view would be useful to
show "active Geospatial Resource pool" i.e. one of the 'selections' we
are discussing.

--adrian

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