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Compound node layout [message #1793705]

Tue, 14 August 2018 11:27

Christophe De Loor

Messages: 9
Registered: May 2018

Junior Member

Hi,

I have a graph which consists of several nodes which are connected to another set of nodes, but will never be interconnected between themselves.
A simple example is shown here:
index.php/fa/33632/0/

The three nodes on the left are connected to 1 or more nodes, but can never be connected to eachother.

I wanted to make a clear distinction between these 2 'types' of nodes by adding a parent node around the nodes, as shown here:
index.php/fa/33634/0/

After adding the parent node, the boundary between the nodes was layouted completely different, I assume it has something to do with the routing of hierarchical nodes. Are there options I can set on the graph/edges so a similar layout is generated with or without the parent node?

Best regards,
Christophe

Attachment: example_graph.png
(Size: 5.76KB, Downloaded 311 times)
Attachment: example_graph_parent.png
(Size: 20.74KB, Downloaded 289 times)

[Updated on: Tue, 14 August 2018 11:30]

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Re: Compound node layout [message #1793707 is a reply to message #1793705]

Tue, 14 August 2018 11:47

Christoph Daniel Schulze

Messages: 98
Registered: September 2015

Member

Hi Christophe!

I'm not sure what you mean by "the boundary between the nodes was layouted completely different", but yes, introducing hierarchy into a diagram fundamentally changes the layout problem and can thus yield vastly different results. Also, hierarchy-crossing edges are not supported without setting additional options.

One thing you may thus want to try though is setting hierarchy handling to INCLUDE_CHILDREN on the outermost node. Usually, our layout algorithm would first layout the content of your hierarchical node and then layout the graph the hierarchical node is contained in. Setting this option makes it layout the whole graph at once, thus also providing support for hierarchy-crossing edges.

Hope this helps!

Cheers,
Chris

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Re: Compound node layout [message #1793805 is a reply to message #1793707]

Thu, 16 August 2018 06:43

Christophe De Loor

Messages: 9
Registered: May 2018

Junior Member

Hi Chris,

Thanks for the quick reply. I was already using INCLUDE_CHILDREN setting on the outermost node. With this, I would expect the layout of the graph to be identical to a flat graph structure (without hierarchical nodes), but this isn't the case. It seems to me the hierarchical edges are given way less priority compared to the other edges.

Best regards,
Christophe

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Re: Compound node layout [message #1793807 is a reply to message #1793805]

Thu, 16 August 2018 07:38

Christoph Daniel Schulze

Messages: 98
Registered: September 2015

Member

Christophe De Loor wrote on Thu, 16 August 2018 06:43

With this, I would expect the layout of the graph to be identical to a flat graph structure

Sadly, that's not how things work. Layout involving hierarchical nodes is a lot more complicated than the layout of a flat graph.

If you show us an example layout as produced by ELK we might be able to suggest different settings.

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Re: Compound node layout [message #1793826 is a reply to message #1793807]

Thu, 16 August 2018 14:49

Christophe De Loor

Messages: 9
Registered: May 2018

Junior Member

Hi Chris,

Attached are 2 images, one where hierarchical layout is used (the parent node is not rendered, so I've added it as a red rectangle), and one with a flat layout.

The boundary between the 4 nodes on the left and the rest of the graph is very different between the 2 cases, ideally I'd like them to be identical.

Maybe some background on why I've added the hierarchical node: I want to show several nodes always on the left side of the graph, using a hierarchical node which contains the rest of the graph realises this.

Best regards,
Christophe

Attachment: example_flat_layout_annotated.png
(Size: 40.21KB, Downloaded 118 times)
Attachment: example_hierarchical_layout_annotated.png
(Size: 32.01KB, Downloaded 113 times)

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Re: Compound node layout [message #1794092 is a reply to message #1793826]

Thu, 23 August 2018 12:12

Christoph Daniel Schulze

Messages: 98
Registered: September 2015

Member

Christophe De Loor wrote on Thu, 16 August 2018 14:49

Maybe some background on why I've added the hierarchical node: I want to show several nodes always on the left side of the graph, using a hierarchical node which contains the rest of the graph realises this.

I was hoping for something like this. :) We have a setting to constrain nodes to the left or right boundary of the graph: the layer constraint. Set it to FIRST on the nodes that should appear on the left side and see if that does what you're trying to accomplish through hierarchy.

Cheers,
Chris

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Re: Compound node layout [message #1794141 is a reply to message #1794092]

Fri, 24 August 2018 09:44

Christophe De Loor

Messages: 9
Registered: May 2018

Junior Member

Thanks for the help.

It does work more or less, but my graph can also contain disjunct graphs, and then the graphs are shown side by side (see this topic I made previously: https://www.eclipse.org/forums/index.php/t/1093514/) .

I was able to solve this issue by adding a stub node which connects all the components I want to show on the left, together with setting shortness priority setting on the edges connected to the stub node. However, with bigger graphs, this doesn't work consistently anymore + the graph was shifted more and more to the right by the amount of edges connected to the stub node.

Christophe

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