Structure View
The Structure View implementation used for a specific file type can be customized on many levels. If a custom language plugin provides an implementation of the StructureView interface, it can completely replace the standard structure view implementation with a custom user interface component. However, for most languages, this is not necessary, and the standard StructureView implementation provided by IntelliJ Platform can be reused.
The starting point for the structure view is the PsiStructureViewFactory interface, which is registered in the com.intellij.lang.psiStructureViewFactory extension point.
Examples:
To reuse the IntelliJ Platform implementation of the StructureView, the plugin returns a TreeBasedStructureViewBuilder from its PsiStructureViewFactory.getStructureViewBuilder() method. As the builder model, the plugin can specify a subclass of TextEditorBasedStructureViewModel, and by overriding methods of this subclass, it customizes the structure view for a specific language.
Example: StructureViewModel for Properties language plugin
The main method to override is getRoot(), which returns the instance of a class implementing the StructureViewTreeElement interface. There exists no standard implementation of this interface, so a plugin will need to implement it completely.
The structure view tree is usually built as a partial mirror of the PSI tree. In the implementation of StructureViewTreeElement.getChildren(), the plugin can specify which of the child elements of a specific PSI tree node need to be represented as elements in the structure view. Another important method is getPresentation(), which can be used to customize the text, attributes, and icon used to represent an element in the structure view.
The implementation of StructureViewTreeElement.getChildren() needs to be matched by TextEditorBasedStructureViewModel.getSuitableClasses(). The latter method returns an array of PsiElement-derived classes, which can be shown as structure view elements. It is used to select the Structure View item matching the cursor position when the structure view is first opened or when the Autoscroll from source option is enabled.
Example: StructureViewTreeElement for Properties language plugin