Combination of Different Layout Approaches

In an interactive environment such as a visual language editor, it is not sufficient to apply the same layout algorithm in every situation. Instead, the user often wants to select the layout behavior at runtime. With the approach presented, the user can control the layout behavior by choosing different layout patterns for different parts of a diagram, e.g., a graph drawing algorithm may be applied to some selected components while others are aligned vertically or horizontally. To enable the specification of layout behavior, we introduced the concept of layout patterns in previous work. Each layout pattern encapsulates certain layout behavior, and hence enables modularization and reuse. To specify user-controlled layout behavior, a flexible combination of arbitrary layout patterns needs to be enabled. Therefore, we introduce an approach that is capable of combining diverse layout approaches, such as standard graph drawing algorithms, constraint-based algorithms, or rule-based layout algorithms. More specifically, an algorithm is presented that automatically computes the complete layout in a straightforward way.