Dynamic Ghost Node Creation (glsp-node-server)

[jmenzies12]

Hey folks,

Is it possible to make the ghost node creation dynamic?

The code to create the ghost nodes, defined under JsonCreateNodeOperationHandler is triggered when the diagram is opened. That means that we are unable to change the color of the node dynamically based on a vscode preference,

Currently we do something similar to this, but if the preference changes whilst the diagram is open the ghost element does not get refreshed so it keeps the previously set color.

Example code:

    override createTriggerGhostElement(): GhostElement | undefined {
    const nodeSize = calculateNodeSize(this.elementTypeIds[0] as NodeType)

	const builder = GNode.builder()
		.type(this.elementTypeIds[0])
		.id('GGHOST')
		.addCssClass('node')
		.layout('hbox')
		.size(nodeSize.width, nodeSize.height)
		.addLayoutOptions({ prefWidth: nodeSize.width, prefHeight: nodeSize.height })
		.position(Point.ORIGIN)
		.addArg('color', nodeColor)
	return { template: builder.build() }
}

Cheers
Jonathan

[tortmayr]

@martin-fleck-at Can you please have a look at this?

[martin-fleck-at]

@jmenzies12 So when we introduced the ghost elements we already introduced a dynamic flag that the server can set that so that the tool palette may reload the palette and re-request the palette items with the ghost elements in them.

So the first thing you need to do is to make sure that you set the dynamic flag in our server, e.g.:

override createTriggerGhostElement(): GhostElement | undefined {
      ...
      return { template: builder.build(), dynamic: true };
}

(for instance, we also do this for our create task handlers).

Now the question is how to trigger the reloadPaletteBody from the tool palette as it only listens to SetModelAction and UpdateModelAction at the moment. I'd say that there are three options:

• CSS Variable: Don't resolve the color server-side at all. Map the preference to a CSS custom property; the ghost renders through the same view as the real node, so everything updates instantly with no round trip. Not sure if that is an option for you.
• Custom ToolPalette: Subclass ToolPalette to call reloadPaletteBody() on your own preference-changed action. This should be fairly straight-forward and you could define other triggers as well.
• Dummy Update: When changing the preference, trigger a model update by sending an UpdateModelAction. Not really recommended.

We might want to consider creating a dedicated refresh action for the palette so it can be triggered from other places as well but for now this should help you get started. If you have any further questions, please let me know.

[jmenzies12]

Thank you @martin-fleck-at! We'll look into these suggestion and see what works best for us. Will let you know how it works out