Implement scrollable::snap_to operation

native/src/widget/operation.rs

@@ -1,4 +1,9 @@
-use crate::widget::state;
+pub mod focusable;
+pub mod scrollable;
+
+pub use focusable::Focusable;
+pub use scrollable::Scrollable;
+
 use crate::widget::Id;
 
 pub trait Operation<T> {
@@ -8,12 +13,9 @@ pub trait Operation<T> {
         operate_on_children: &mut dyn FnMut(&mut dyn Operation<T>),
     );
 
-    fn focusable(
-        &mut self,
-        _state: &mut dyn state::Focusable,
-        _id: Option<&Id>,
-    ) {
-    }
+    fn focusable(&mut self, _state: &mut dyn Focusable, _id: Option<&Id>) {}
+
+    fn scrollable(&mut self, _state: &mut dyn Scrollable, _id: Option<&Id>) {}
 
     fn finish(&self) -> Outcome<T> {
         Outcome::None
@@ -25,160 +27,3 @@ pub enum Outcome<T> {
     Some(T),
     Chain(Box<dyn Operation<T>>),
 }
-
-pub fn focus<T>(target: Id) -> impl Operation<T> {
-    struct Focus {
-        target: Id,
-    }
-
-    impl<T> Operation<T> for Focus {
-        fn focusable(
-            &mut self,
-            state: &mut dyn state::Focusable,
-            id: Option<&Id>,
-        ) {
-            match id {
-                Some(id) if id == &self.target => {
-                    state.focus();
-                }
-                _ => {
-                    state.unfocus();
-                }
-            }
-        }
-
-        fn container(
-            &mut self,
-            _id: Option<&Id>,
-            operate_on_children: &mut dyn FnMut(&mut dyn Operation<T>),
-        ) {
-            operate_on_children(self)
-        }
-    }
-
-    Focus { target }
-}
-
-#[derive(Debug, Clone, Copy, PartialEq, Eq, Default)]
-pub struct FocusCount {
-    focused: Option<usize>,
-    total: usize,
-}
-
-pub fn count_focusable<T, O>(f: fn(FocusCount) -> O) -> impl Operation<T>
-where
-    O: Operation<T> + 'static,
-{
-    struct CountFocusable<O> {
-        count: FocusCount,
-        next: fn(FocusCount) -> O,
-    }
-
-    impl<T, O> Operation<T> for CountFocusable<O>
-    where
-        O: Operation<T> + 'static,
-    {
-        fn focusable(
-            &mut self,
-            state: &mut dyn state::Focusable,
-            _id: Option<&Id>,
-        ) {
-            if state.is_focused() {
-                self.count.focused = Some(self.count.total);
-            }
-
-            self.count.total += 1;
-        }
-
-        fn container(
-            &mut self,
-            _id: Option<&Id>,
-            operate_on_children: &mut dyn FnMut(&mut dyn Operation<T>),
-        ) {
-            operate_on_children(self)
-        }
-
-        fn finish(&self) -> Outcome<T> {
-            Outcome::Chain(Box::new((self.next)(self.count)))
-        }
-    }
-
-    CountFocusable {
-        count: FocusCount::default(),
-        next: f,
-    }
-}
-
-pub fn focus_previous<T>() -> impl Operation<T> {
-    struct FocusPrevious {
-        count: FocusCount,
-        current: usize,
-    }
-
-    impl<T> Operation<T> for FocusPrevious {
-        fn focusable(
-            &mut self,
-            state: &mut dyn state::Focusable,
-            _id: Option<&Id>,
-        ) {
-            if self.count.total == 0 {
-                return;
-            }
-
-            match self.count.focused {
-                None if self.current == self.count.total - 1 => state.focus(),
-                Some(0) if self.current == 0 => state.unfocus(),
-                Some(0) => {}
-                Some(focused) if focused == self.current => state.unfocus(),
-                Some(focused) if focused - 1 == self.current => state.focus(),
-                _ => {}
-            }
-
-            self.current += 1;
-        }
-
-        fn container(
-            &mut self,
-            _id: Option<&Id>,
-            operate_on_children: &mut dyn FnMut(&mut dyn Operation<T>),
-        ) {
-            operate_on_children(self)
-        }
-    }
-
-    count_focusable(|count| FocusPrevious { count, current: 0 })
-}
-
-pub fn focus_next<T>() -> impl Operation<T> {
-    struct FocusNext {
-        count: FocusCount,
-        current: usize,
-    }
-
-    impl<T> Operation<T> for FocusNext {
-        fn focusable(
-            &mut self,
-            state: &mut dyn state::Focusable,
-            _id: Option<&Id>,
-        ) {
-            match self.count.focused {
-                None if self.current == 0 => state.focus(),
-                Some(focused) if focused == self.current => state.unfocus(),
-                Some(focused) if focused + 1 == self.current => state.focus(),
-                _ => {}
-            }
-
-            self.current += 1;
-        }
-
-        fn container(
-            &mut self,
-            _id: Option<&Id>,
-            operate_on_children: &mut dyn FnMut(&mut dyn Operation<T>),
-        ) {
-            operate_on_children(self)
-        }
-    }
-
-    count_focusable(|count| FocusNext { count, current: 0 })
-}