[udig-devel] LayerDecorator and LayerListener/LayerEvent

[Jody Garnett <jgarnett@xxxxxxxxxxxxxxx>]

I have been attempting to hook up StyleView to the layer notification 
system. StyleView works by having a clone of the layer blackboard which 
it needs to keep in sync with updates from the layer, while only pushing 
changes back during the application of a style change.

The class SelectionLayer already provides a layer decorator (aka an 
Object that operates as a wrapper on a layer while maintaining the same 
interface).

SelectionLayer pretends to be the original layer while replacing the 
existing StyleBlackboard with one specifically designed to render things 
in Orange.
StyleLayer pretends to be the original layer while replacing the 
existing StyleBlackboard with one that can be edited.

Since this is a common use I have taken the boilerplate code into 
LayerDecorator.

The other addition is the need to listen to modifications on the layer, 
right now layer makes use of EMF "adapters" which are like the listeners 
everyone knows and loves.
Jesse has promised me normal listeners for a while, now today I have 
defined the interface and make use of it for StyleLayer.  The 
implementation will forward any events from the original layer in 
addition to indicating changes to the local clone of the blackboard.

This work replaces the concept of StyleTransaction, StyleTransaction 
made allowances for editing multiple layers. This can still be 
accomplished - simply wraps multiple Layers (each in its own StyleLayer).

I hope this makes sense to all involved.
Jody