Module function_menu

FoldExplorerMinorMode and FoldExplorerMenu use Stani's fold explorer idea to display a subset of the fold hierarchy of the file.

Scintilla has language lexers built in to the C code that are capable of doing a lot of preprocessing of the source file. It's typically used for syntax highlighting, but it can also extended to generate a nested list of items that have some hierarchical relationship.

We can exploit that here to display a function list.