Returns the index paths for any supplementary views that the layout object wants to add to the collection view.
- macOS 10.11+
The type of the supplementary views to add.
The set of
NSIndex objects representing the supplementary views to insert, or an empty array if you do not want to insert any supplementary views.
When your app inserts or deletes items or sections in the collection view, the collection view calls this method for each of the registered supplementary view types. The default implementation returns an empty array, but you can override it and return index paths for each supplementary view you want to add. For example, when a section is added, you might want to add the supplementary views that belong in that section. In that case, you would add index paths to the array that contain the section numbers that were added.
The index paths you return should always contain a valid section number, but the item number is optional. The item number is necessary only if you support multiple supplementary views of the same type in a single section. If you do, your layout object can use the item numbers internally to differentiate the supplementary views.
Subclasses are expected to override this method, as needed, and provide any appropriate index paths.