SimControl/libs/CLI11/book/chapters/toolkits.md

Using CLI11 in a Toolkit

CLI11 was designed to be integrate into a toolkit, providing a native experience for users. This was used in GooFit to provide GooFit::Application, an class designed to make ROOT users feel at home.

Custom namespace

If you want to provide CLI11 in a custom namespace, you'll want to at least put using CLI::App in your namespace. You can also include Option, some errors, and validators. You can also put using namespace CLI inside your namespace to import everything.

You may also want to make your own copy of the CLI11_PARSE macro. Something like:

 #define MYPACKAGE_PARSE(app, argv, argc)    \
     try {                                   \
         app.parse(argv, argc);              \
     } catch(const CLI::ParseError &e) {     \
         return app.exit(e);                 \
     }

Subclassing App

If you subclass App, you'll just need to do a few things. You'll need a constructor; calling the base App constructor is a good idea, but not necessary (it just sets a description and adds a help flag.

You can call anything you would like to configure in the constructor, like option_defaults()->take_last() or fallthrough(), and it will be set on all user instances. You can add flags and options, as well.

Virtual functions provided

You are given a few virtual functions that you can change (only on the main App). pre_callback runs right before the callbacks run, letting you print out custom messages at the top of your app.