Package diva.graph.layout

A graph layout package which provides static and incremental node layout and edge routing facilities. This package depends on the package diva.graph.model for defining a graph's topology and graph update events, but has no dependency on the specific implementation of the graph's visual representation. It states certain assumptions about information that it needs to complete its layout (e.g. a viewport, bounding boxes for nodes, and paths for edges) through the interfaces LayoutEnvironment, LayoutNode, LayoutEdge, and PathLayoutEdge. The diva.graph package satisfies these assumptions.

The interfaces for layout engines are specified by StaticLayout and IncrementalLayout, which perform static and incremental layout on the graph, respectively. Static layouts traverse the graph structure and perform layout from scratch, ignoring the previous positions of the nodes in the graphs. Incremental layouts are performed as the graph topology is modified and attempt to preserve the visual continuity of the layout. They are notified of graph modifications via the GraphListener interface.

Edge routing is specified by the interfaces StaticPathRouter and DynamicPathRouter which are somewhat analogous to the two flavors of layout. The StaticPathRouter interface specifies a routing engine that can route a path edge between two nodes statically (i.e. from scratch, ignoring the previous positions of the endpoint nodes); the DynamicPathRouter specifies a routing engine that can dynamically adjust an already-routed path edge as one of its endpoint-nodes is moved (e.g. by the user dragging a node around).

NOTE: How do we handle users interactively editing the middle of an edge's path and collapsing multiple edges?

Interface Summary

Interface	Description
GlobalLayout	A static layout engine which layouts traverse the graph structure and performs layout from scratch, ignoring the previous positions of the nodes in the graphs.
IncrementalLayout	A layout engine which operates incrementally, based on the arrival of new node information.
LayoutTarget	The basic set of information necessary to layout a graph: a mapping the graph data structure to aspects of its visual representation, a viewport to layout in, and some manipulation routines including pick, place, and route.

Class Summary

Class	Description
AbstractGlobalLayout	An abstract implementation of the GlobalLayout interface.
GridAnnealingLayout	A simple layout which places nodes on a grid using a cost function.
IncrementalLayoutListener	A Listener that applies the given incremental layout whenever a graph event is received.
IncrLayoutAdapter	An adapter to make global layouts incremental.
LayoutUtilities	Miscellaneous utility routines used in layout.
LevelLayout	A level-based layout algorithm originally implemented by Ulfar Erlingsson at Cornell/RPI and modified to fit into this system.
LevelLayout.LevelInfo	The semantic object of each node in the graph copy that is being laid out.
ProxyIncrLayout	A proxy layout which forwards all events to a given incremental layout delegate.
RandomIncrLayout	Randomly place newly-added nodes within the target viewport.
RandomLayout	A static random layout engine.