Merge pull request #1526 from mtkennerly/feature/find-focused

Add widget operation to find currently focused widget

Author: hecrj

native/src/widget/operation/focusable.rs

@@ -167,3 +167,37 @@ pub fn focus_next<T>() -> impl Operation<T> {
 
     count(|count| FocusNext { count, current: 0 })
 }
+
+/// Produces an [`Operation`] that searches for the current focused widget
+/// and stores its ID. This ignores widgets that do not have an ID.
+pub fn find_focused() -> impl Operation<Id> {
+    struct FindFocused {
+        focused: Option<Id>,
+    }
+
+    impl Operation<Id> for FindFocused {
+        fn focusable(&mut self, state: &mut dyn Focusable, id: Option<&Id>) {
+            if state.is_focused() && id.is_some() {
+                self.focused = id.cloned();
+            }
+        }
+
+        fn container(
+            &mut self,
+            _id: Option<&Id>,
+            operate_on_children: &mut dyn FnMut(&mut dyn Operation<Id>),
+        ) {
+            operate_on_children(self)
+        }
+
+        fn finish(&self) -> Outcome<Id> {
+            if let Some(id) = &self.focused {
+                Outcome::Some(id.clone())
+            } else {
+                Outcome::None
+            }
+        }
+    }
+
+    FindFocused { focused: None }
+}

native/src/widget/scrollable.rs

@@ -334,6 +334,12 @@ impl Id {
     }
 }
 
+impl From<Id> for widget::Id {
+    fn from(id: Id) -> Self {
+        id.0
+    }
+}
+
 /// Produces a [`Command`] that snaps the [`Scrollable`] with the given [`Id`]
 /// to the provided `percentage`.
 pub fn snap_to<Message: 'static>(id: Id, percentage: f32) -> Command<Message> {

native/src/widget/text_input.rs

@@ -333,6 +333,12 @@ impl Id {
     }
 }
 
+impl From<Id> for widget::Id {
+    fn from(id: Id) -> Self {
+        id.0
+    }
+}
+
 /// Produces a [`Command`] that focuses the [`TextInput`] with the given [`Id`].
 pub fn focus<Message: 'static>(id: Id) -> Command<Message> {
     Command::widget(operation::focusable::focus(id.0))