FixGroupLayoutStage

This stage guarantees that a core layout algorithm will maintain the relative positions of nodes within the same group.

Also, this stage is responsible for routing edges that connect nodes belonging to hierarchically unrelated groups. More precisely, the stage temporarily replaces fixed group nodes (see FIXED_GROUP_NODES_DP_KEY) with normal nodes of the same size while the content of the groups is removed from the graph during layout.

The nodes are used as placeholders and are responsible for keeping the relations to the remaining graph elements. Edges that originate from the outside of the group node and terminate in its interior (inter-edges) are redirected such that they connect to the node that replaces the group.

After the layout process, the group nodes are restored and the stage inserts the content at the new group position (derived from the position of the associated node). The content itself (including the edges between content nodes) remains unchanged and is only relocated. Furthermore, the inter-edges are connected to their original source/target and the stage reroutes them using the specified inter-edge routing algorithm (see interEdgeRouter).

Initial graph. Nodes inside groups have to remain at their relative positions. Example after using FixGroupLayoutStage with OrthogonalLayout. Nodes inside groups did not change relative positions.