Implement scrollable::snap_to operation

native/src/widget/operation/scrollable.rs

@@ -0,0 +1,30 @@
+use crate::widget::{Id, Operation};
+
+pub trait Scrollable {
+    fn snap_to(&mut self, percentage: f32);
+}
+
+pub fn snap_to<T>(target: Id, percentage: f32) -> impl Operation<T> {
+    struct SnapTo {
+        target: Id,
+        percentage: f32,
+    }
+
+    impl<T> Operation<T> for SnapTo {
+        fn scrollable(&mut self, state: &mut dyn Scrollable, id: Option<&Id>) {
+            if Some(&self.target) == id {
+                state.snap_to(self.percentage);
+            }
+        }
+
+        fn container(
+            &mut self,
+            _id: Option<&Id>,
+            operate_on_children: &mut dyn FnMut(&mut dyn Operation<T>),
+        ) {
+            operate_on_children(self)
+        }
+    }
+
+    SnapTo { target, percentage }
+}