Map View

[1] Overview

The map view renders a portion of the world model on screen.

[2] Dependencies

* Map Engine (--> mapengine.txt)
* Graphics (--> graphics.txt)

[3] Requirements

* The mapview contains a cache of the graphics needed to render the
  model. It works with a reference count, discarding unused graphics
  after the cache reaches a certain size.
* Multiple instances of the mapview may be active at any time.
* The portion of the map being rendered is controlled by a python
  script that runs periodically.
  
[4] References