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//! Query or update internal widget state.
pub mod focusable;
pub mod scrollable;
pub use focusable::Focusable;
pub use scrollable::Scrollable;
use crate::widget::Id;
use std::fmt;
/// A piece of logic that can traverse the widget tree of an application in
/// order to query or update some widget state.
pub trait Operation<T> {
/// Operates on a widget that contains other widgets.
///
/// The `operate_on_children` function can be called to return control to
/// the widget tree and keep traversing it.
fn container(
&mut self,
id: Option<&Id>,
operate_on_children: &mut dyn FnMut(&mut dyn Operation<T>),
);
/// Operates on a widget that can be focused.
fn focusable(&mut self, _state: &mut dyn Focusable, _id: Option<&Id>) {}
/// Operates on a widget that can be scrolled.
fn scrollable(&mut self, _state: &mut dyn Scrollable, _id: Option<&Id>) {}
/// Finishes the [`Operation`] and returns its [`Outcome`].
fn finish(&self) -> Outcome<T> {
Outcome::None
}
}
/// The result of an [`Operation`].
pub enum Outcome<T> {
/// The [`Operation`] produced no result.
None,
/// The [`Operation`] produced some result.
Some(T),
/// The [`Operation`] needs to be followed by another [`Operation`].
Chain(Box<dyn Operation<T>>),
}
impl<T> fmt::Debug for Outcome<T>
where
T: fmt::Debug,
{
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
match self {
Self::None => write!(f, "Outcome::None"),
Self::Some(output) => write!(f, "Outcome::Some({:?})", output),
Self::Chain(_) => write!(f, "Outcome::Chain(...)"),
}
}
}
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