[jboss-jira] [JBoss JIRA] (DROOLS-3139) [DMN Designer] Automatic Layout Feature

[Jozef Marko (Jira)]

Jozef Marko created DROOLS-3139:
-----------------------------------

             Summary: [DMN Designer] Automatic Layout Feature
                 Key: DROOLS-3139
                 URL: https://issues.jboss.org/browse/DROOLS-3139
             Project: Drools
          Issue Type: Epic
          Components: DMN Editor
            Reporter: Jozef Marko
            Assignee: Daniel José dos Santos


DMN Designer should *autolayout* new imported DMN models. The *autolayout* should position DRG diagram nodes into horizontal layers to minimize crossing of connectors with respect of *Top-Down* importance. It means if nodes *Layer B* are inputs for nodes in *Layer A* then the *Layer B* will be below *Layer A*. The *autolayout* should also try to minimize scrolling needed to see whole DRG diagram.

User should also have possibility to invoke *autolayout* feature any time during designing the diagram. In this case the action should be undoable with the *Undo* toolbar button.

The approach used to achieve this is the Sugiyama Method, which is done in 4 steps. Each step have its own set of algorithms. For each step, we selected one of the available algorithms to implement, based on our current needs and time to develop:

*Step 1 - Cycle breaking:* We break cycles in diagram by reversing some edges (they are de-reversed in the end). This step are required because we need ending points in step 2 while sweeping through graph;

*Step 2 - Layering:* We sweep through graph (diagram) and put each node (vertex) in a layer, based on it's distance from others node. For edges that crosses multiple layers, we create virtual vertices connecting those. They are removed at the end.
This approach usually puts the start nodes at the top and the deepest nodes at the end. In the current implementation we're using Longest Path algorithm. A better approach can be developed in future using Network Simplex;

*Step 3 - Node Ordering:* We order each node (vertex) inside its layers in order to reduce crossing, using median. Another approach that can be used is barycenter. 

*Step 4 - Node Positioning:* We de-reverse nodes reversed in step 1 and remove virtual nodes reconnecting the concrete nodes. Then we calculate the position of each node. This step can be divided in two steps: one for horizontal position and other for vertical for better positioning. Currently we're using a simple approach: every block of nodes inside the layers is centered and the distance between layers is the same. So it will produce results like the attachment "Automatic Layout Demo". 



--
This message was sent by Atlassian Jira
(v7.12.1#712002)