DOM development
From autoplot.org
Introduction of DOM. ApplicationModel is gutted, factoring out code into the dom package. ApplicationModel fields are factored out into dom elements like Panel, Axis, DataSourceFilter, and Options. Its methods are factored out into dom element controllers like PanelController and DataSourceFilterController. This allows Autoplot to represent complex states with many panels, and sorts out the mess of code in ApplicationModel out into agents that just what they need to know.
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1. What's a DOM node?
DomNodes should contain either immutable properties (such as String or Datum), or other DomNodes as children. They can contain other fields, but the accessors should not use "get" and "set" which identify properties.
Often nodes will have a getController() method. The controller has methods that affect the node, and contains data implementing the DOM node's state. For example, the Panel node contains information about the dataset and rendering options, but it is the PanelController that contains the das2 Renderer object and ensures it contains the correct QDataSet.
2. Pitfalls
2.1. Node copy
2.1.1. Deep Copy
A deep copy is needed to make state support and serialization work. It's easy to fail to make a deep copy, because clone will create a shallow copy that seems to work.
Solution: Clients should use "copy" to make copies of DOM elements, even though they are Clonable.
2.1.2. Property Change Support Copied
Clone is used for Node copy, which copied the propertyChangeSupport as well. Changes to the copy notified listeners to the original. Same thing for the controller...
Solution: All nodes should call the DomNode base class' copy, which will clone and replace the propertyChangeSupport. This means copy is no longer abstract, and implementers must be careful to copy and not clone when children exist.
2.1.3. Initialization actions in Constructor
Stuff happens (renaming the property change events) in the constructor, so the copy needs to do this as well.
2.2. Panels and Plots identity
copy and sync need to preserve object identity in copy and sync.
Solution: be careful and assert getPanels().contains(getPanel())
