Using constraints to achieve stability in automatic graph layout algorithms

Automatic layout algorithms are commonly used when displaying graphs on the screen because they provide a “nice” drawing of the graph without user intervention. There are, however, a couple of disadvantages to automatic layout. Without user intervention, an automatic layout algorithm is only capable of producing an aesthetically pleasing drawing of the graph. User- or application-specified layout constraints (often concerning the semantics of a graph) are difficult or impossible to specify. A second problem is that automatic layout algorithms seldom make use of information in the current layout when calculating the new layout. This can also be frustrating to the user because whenever a new layout is done, the user's orientation in the graph is lost. This paper suggests using layout constraints to solve both of these problems. We show how user-specified layout constraints may be easily added to many automatic graph layout algorithms. Additionally, the constraints specified by the current layout are used when calculating the new layout to achieve a more stable layout. This approach allows a continuum between manual and automatic layout by allowing the user to specify how stable the graph's layout should be.

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