Tree views are a proven way of showing and navigating structure in IDEs. MPS of course has several of them for various purposes. We have now added a nice tree view that can be used for various tasks. The screenshot below shows a call stack for functions.

Selecting a node in the tree automatically selects the corresponding node in the editor. In addition, tree nodes can contribute user-defined actions that are shown in the context menu. As with visualizations, a node can contribute different categories of tree views. All of this can be defined without dealing with any Swing code. The code below shows the implementation of the callgraph; the framework is part of the platform and can be used for any MPS language.