1 files changed, 31 insertions, 0 deletions
diff --git a/native/src/widget/operation.rs b/native/src/widget/operation.rs
index 4a075da9..ef636aa2 100644
--- a/native/src/widget/operation.rs
+++ b/native/src/widget/operation.rs
@@ -1,3 +1,4 @@
+//! Query or update internal widget state.
 pub mod focusable;
 pub mod scrollable;
 
@@ -6,24 +7,54 @@ 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(...)"),
+        }
+    }
+}