Macro wrap_focus_handler 

macro_rules! wrap_focus_handler {
    ($ vis : vis struct $ name : ident ; impl FocusHandler { $ ($ (# [$ attrs_name : meta]) * fn $ method_name : ident (& $ self : ident $ (, $ arg_name : ident : $ arg_type : ty) * $ (,) ?) $ (-> $ return_type : ty) ? { $ ($ body : tt) * }) * }) => { ... };
    ($ vis : vis struct $ name : ident $ (< $ ($ generic_type : ident : $ first_generic_type_bound : tt $ (+ $ generic_type_bound : tt) *) , + $ (,) ? >) ? { $ ($ field_vis : vis $ field_name : ident : $ field_type : ty) , * $ (,) ? } impl FocusHandler { $ ($ (# [$ attrs_name : meta]) * fn $ method_name : ident (& $ self : ident $ (, $ arg_name : ident : $ arg_type : ty) * $ (,) ?) $ (-> $ return_type : ty) ? { $ ($ body : tt) * }) * }) => { ... };
}

Implement the WrapFocusHandler trait for the specified struct. You can declare more members for your struct, and in the impl FocusHandler block you can override default methods implemented by the ImplFocusHandler trait.

Example

wrap_focus_handler! {
    struct MyFocusHandler {
        payload: String,
    }

    impl FocusHandler {
        // ...
    }
}

fn make_my_struct() -> FocusHandler {
    MyFocusHandler::new("payload".to_string())
}