How to work with Scopes when using Workspaces in TornadoFX?

Question

I'm using the Workspace feature of TornadoFX and I'm trying to make them work with Scopes. When I'm starting up the application I need to set some things up and when it is done I start the TornadoFX application and I supply a Scope to my first view. After that I want to be able to dock other views into my Workspace in a new Scope but this doesn't work for some reason: the original View doesn't get undocked but the new View gets docked I just don't see it on the screen. What could be the problem? Here is my code to reproduce the problem:

fun main(args: Array<String>) {
    Application.launch(TestApp::class.java, *args)
}


class ParentScope : Scope() {
    val id = UUID.randomUUID().toString().substring(0, 4)
}

class ChildScope : Scope() {
    val id = UUID.randomUUID().toString().substring(0, 4)
}

class TestApp : App(Workspace::class) {

    override fun onBeforeShow(view: UIComponent) {
        workspace.dock<ParentView>(ParentScope())
    }
}

class ParentView : View("parent") {

    override val scope = super.scope as ParentScope

    override val root = hbox {
        button("new child") {
            action {
                workspace.dock<ChildView>(ChildScope())
            }
        }
    }

    override fun onDock() {
        logger.info("Docking parent (${scope.id})")
    }

    override fun onUndock() {
        logger.info("Undocking parent (${scope.id})")
    }

}

class ChildView : View("child") {

    override val scope = super.scope as ChildScope

    override val root = hbox {
        text("In child")
    }

    override fun onDock() {
        logger.info("Docking child (${scope.id})")
    }

    override fun onUndock() {
        logger.info("Undocking child (${scope.id})")
    }

}

The output after I click thew new child button is this:

10:56:19.415 [JavaFX Application Thread] INFO  Test - Docking parent (d202) 
10:56:23.967 [JavaFX Application Thread] INFO  Test - Docking child (cbc5)

What I see is the same ParentView. If I click new child again the ChildView gets undocked and a new ChildView gets docked but I still only see the ParentView:

10:56:31.228 [JavaFX Application Thread] INFO  Test - Undocking child (cbc5)
10:56:31.228 [JavaFX Application Thread] INFO  Test - Docking child (1dd8)

Answer 1

The App already defines a Scope with a corresponding Workspace instance, so while your initial View is docked in the Workspace, your new ParentScope defines a new Workspace instance. When you dock the ChildView into that Workspace it does exactly that, but the Workspace in question is not shown on screen.

To remedy this you can override the primary scope of the your application like this:

class TestApp : WorkspaceApp(ParentView::class) {
    init {
        scope = ParentScope()
    }
}

Notice also that I use the WorkspaceApp subclass so I don't need to dock the ParentView manually.

While looking at this issue I realized that if you dock a UIComponent into a Workspace, it should assume the Workspace it has been docked in. For that reason, I've committed a fix so that your initial code will work without modification.