A `Keyboard_event_handler.t` is a collections of actions (commands and disabled keys) that can be used to handle keyboard events and to produce help text.

`module Condition : sig ... end`
`module Handler : sig ... end`
`module Command : sig ... end`
`module Action : sig ... end`
`type t`````
`include sig ... end`
`val sexp_of_t : t ‑> Base.Sexp.t`
`val empty : t`
`val of_action_list_exn : Action.t list ‑> t`

`of_action_list_exn` and `of_command_list_exn` create a keyboard event handler from a list of actions. If the same key appears in multiple actions, an exception is raised.

`val of_command_list_exn : Command.t list ‑> t`
`val add_action_exn : t ‑> Action.t ‑> t`

`add_action_exn`, `add_command_exn`, and `add_disabled_key_exn` add a new action to a keyboard event handler. If any key from the new action already exists in the handler, an exception is raised.

`val add_command_exn : t ‑> Command.t ‑> t`
`val add_disabled_key_exn : t ‑> Incr_dom_widgets.Keystroke.t ‑> t`
`val set_action : t ‑> Action.t ‑> t`

`set_action`, `set_command`, and `set_disabled_key` are similar to their respective `*_exn` functions, but if a key from the new action already exists in the handler, that key's action is updated to the new action.

`val set_command : t ‑> Command.t ‑> t`
`val set_disabled_key : t ‑> Incr_dom_widgets.Keystroke.t ‑> t`
`val merge_exn : t ‑> t ‑> t`

`merge_exn t1 t2` and `merge t1 t2` create a new keyboard event handler containing the actions from both `t1` and `t2`. If there is a duplicate key between `t1` and `t2`, `merge_exn` raises an exception while `merge` uses the action from `t2`.

`val merge : t ‑> t ‑> t`
`val handle_event : t ‑> Incr_dom_widgets.Keyboard_event.t ‑> Virtual_dom.Vdom.Event.t option`
`val get_help_text : ?⁠include_disabled_keys:unit ‑> t ‑> Incr_dom_widgets.Help_text.t`
`val get_grouped_help_text : ?⁠include_disabled_keys:unit ‑> t ‑> default_group:Incr_dom_widgets.Grouped_help_text.Group_name.t ‑> Incr_dom_widgets.Grouped_help_text.t`
`val get_grouped_help_text_exn : ?⁠include_disabled_keys:unit ‑> t ‑> Incr_dom_widgets.Grouped_help_text.t`