Enable both text and graphical views of generated content in the Playground

[kolovos]

At the moment, generated textual content (e.g. through EGL, EGX and Pinset) can only be shown in a textual or graphical view. For text that we can render (e.g. HTML, PlantUML etc.) it would be nice to allow the user to switch between the two in the same way that we allow users to see the textual graphical/representation of models/metamodels. Most of the code is already there (OutputPanel is a subclass of ModelPanel) so that shouldn't be too difficult.

[dandelion-lowcode]

On a related note, I sometimes find the PlantUML display a bit overwhelming, e.g., in https://eclipse.dev/epsilon/playground/?callcentre2minivoicexml. I tinkered a model tree view with Metro UI imitating that of Eclipse that could be embedded on the Target Model view: https://codepen.io/jnxf/pen/RNbMOjM.

To incorporate this into the playground, the EpsilonExecutionResponse backend should not only return the PlantUML source, but also a serialization of the model. I managed to do it with emfjson-jackson with a code like this one:

import org.eclipse.emfcloud.jackson.module.EMFModule;
import com.fasterxml.jackson.databind.ObjectMapper;

// We want to return a serialized `targetModel`
ObjectMapper mapper = EMFModule.setupDefaultMapper();
JsonResourceFactory factory = new JsonResourceFactory(mapper);
ObjectMapper mapper2 = factory.getMapper();
return mapper2.writeValueAsString(targetModel.getResource());

Emfjson-jackson isn't foolproof:

... but it does the job.

I don't have mental bandwidth these months to create PRs, but I may as well wanted to report on this.

[kolovos]

Thanks for sharing this! I agree that an alternative tree-based representation for models would be a nice feature to have in future versions of the playground.