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// handleable.rs

// *************************************************************************
// * Copyright (C) 2018-2019 Daniel Mueller (deso@posteo.net)              *
// *                                                                       *
// * This program is free software: you can redistribute it and/or modify  *
// * it under the terms of the GNU General Public License as published by  *
// * the Free Software Foundation, either version 3 of the License, or     *
// * (at your option) any later version.                                   *
// *                                                                       *
// * This program is distributed in the hope that it will be useful,       *
// * but WITHOUT ANY WARRANTY; without even the implied warranty of        *
// * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the         *
// * GNU General Public License for more details.                          *
// *                                                                       *
// * You should have received a copy of the GNU General Public License     *
// * along with this program.  If not, see <http://www.gnu.org/licenses/>. *
// *************************************************************************

use std::any::Any;
use std::fmt::Debug;

use crate::MutCap;
use crate::UiEvent;
use crate::UiEvents;


/// A trait representing an object capable of handling events.
pub trait Handleable<E>: Debug
where
  E: 'static,
{
  /// Handle an `Event`.
  ///
  /// The widget has the option to either consume the event and return
  /// nothing, in which no one else will get informed about it, forward
  /// it directly (the default behavior), in which case the its parent
  /// widget will receive it, or return a completely different event.
  #[allow(unused_variables)]
  fn handle(&mut self, event: E, cap: &mut dyn MutCap<E>) -> Option<UiEvents<E>> {
    // By default we just pass through the event, which will cause it to
    // bubble up to the parent.
    Some(event.into())
  }

  /// Handle a custom event.
  #[allow(unused_variables)]
  fn handle_custom(&mut self, event: Box<dyn Any>, cap: &mut dyn MutCap<E>) -> Option<UiEvents<E>> {
    Some(UiEvent::Custom(event).into())
  }

  /// Handle a custom event without transferring ownership of it.
  #[allow(unused_variables)]
  fn handle_custom_ref(&mut self,
                       event: &mut dyn Any,
                       cap: &mut dyn MutCap<E>) -> Option<UiEvents<E>> {
    None
  }
}