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.
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.
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.