// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License in the LICENSE-APACHE file or at:
// https://www.apache.org/licenses/LICENSE-2.0
//! Callback specific code
//!
//! Note that callbacks are added to windows, hence some callback functionality
//! is a detail of the [`Window`] trait.
//!
//! [`Window`]: crate::Window
/// Specifies under which condition a callback is called.