Re: [Geotools-devel] Relation between Map and Renderer

[Cameron S. <csh...@bi...>]

Great to see some discussion on this issue.  I agree with most of what James 
has to say


> How does the following sound:
>
> DataSource : Object from which features can be pulled, backed by
> file/DB/memory/WFS
> Layer : Holds a DataSouce and a Style
> Map : A set of Layers, in a specific order, with the ability to switch
> layers off or change order

I'd prefer to call this "LayerList" - in keeping with the class already by 
that name.

> Renderer : Holds a reference to a map and renders any AOI on request.
Also holds reference to AOI_Model.
Renderer keeps a list of features for it's AoI and only refreshes the list 
when either:
* AoI changed event happens or
* A layer changed event happens (causing only one layer to reload and repaint)
* A layerList changed event happens (eg a layer is deleted from the view)


MapPane: Contains Tool, and Renderer and various models.


> >My main issue is that the difference between Map and Renderer is not
> >obvious to me at this time (in the same way that the difference between
> >FeatureCollection and DataSource seem very small to me). How are we
> >suppose to implements caching in Renderer? If we allow it by the addition
> >of "set" methods, then what would be the difference between a Map and a
> >Renderer?

I think the problem with merging Map and Renderer comes about when you try to 
create 2 views (displays) of the same data.
* If you want a main map with 5 layers, and a locator map with one basemap, 
then you need to LayerList classes, but one AoI class.
* If you want 2 maps viewing the same data, but zooming independantly, then 
you need one LayerList class, and 2 AoI classes.
* And so I could go on with different use cases.

Attached is a rough class diagram of the key classes I think are required.


-- 
Cameron Shorter              http://cameron.shorter.net
Open Source Developer        http://mapbuilder.sourceforge.net
Senior Software Engineer http://www.adi-limited.com/