What is the LayeredMetaDataProvider good for?

[rsoika]

I found that in the workflow java server example in the class WorkflowServerLauncher a LayeredMetaDataProvider is used.

     ElkLayoutEngine.initialize(new LayeredMetaDataProvider());

The class has no comments and also the example is not explained at this point. I never used this component before. What is it good for? Should I use it?

[tortmayr]

Hi @rsoika,

sorry for the late reply.
First the TLDR anwser: This class is used in the context of automated server-side layouting. This is a rather specific usecase and I don't think you need this for your OpenBPMN editor.

More context:

GLSP has an optional feature to support automated server-side layouting. The ELKEngine (and LayeredMetaDataProvider) is used in this context.

In general, it is possible to configure a LayoutEngine on the server side which can be use to autolayout the graphical model on the server side before sending it to the client.

We provide a reusable implementation that uses the powerful Eclipse Layout Kernel (https://eclipse.dev/elk/) under the hood.

In the Workflow example we have a layout engine configured that uses the Layered ELK algorithm. This is setup with the LayeredElkMetadataProvider.

Here is a quick demo:

Note that the entire server layout/automated layout feature is currently mostly undocumented. We are planning on reiterating/extending the GLSP website documentation once the 2.0. release is finalized and hopefully will also be able to add a section that explains the server-side layouting feature in more detail.

[rsoika]

Thanks, yes I understand, and your are right, for the BPMN usecase this is not necessary.