widget: list: impl ListIter for VecDeque

druid/src/widget/list.rs

@@ -15,6 +15,7 @@
 //! Simple list view widget.
 
 use std::cmp::Ordering;
+use std::collections::VecDeque;
 use std::f64;
 use std::sync::Arc;
 
@@ -216,6 +217,77 @@ impl<S: Data, T: Data> ListIter<(S, T)> for (S, Arc<Vec<T>>) {
     }
 }
 
+impl<T: Data> ListIter<T> for Arc<VecDeque<T>> {
+    fn for_each(&self, mut cb: impl FnMut(&T, usize)) {
+        for (i, item) in self.iter().enumerate() {
+            cb(item, i);
+        }
+    }
+
+    fn for_each_mut(&mut self, mut cb: impl FnMut(&mut T, usize)) {
+        let mut new_data = VecDeque::with_capacity(self.data_len());
+        let mut any_changed = false;
+
+        for (i, item) in self.iter().enumerate() {
+            let mut d = item.to_owned();
+            cb(&mut d, i);
+
+            if !any_changed && !item.same(&d) {
+                any_changed = true;
+            }
+            new_data.push_back(d);
+        }
+
+        if any_changed {
+            *self = Arc::new(new_data);
+        }
+    }
+
+    fn data_len(&self) -> usize {
+        self.len()
+    }
+}
+
+// S == shared data type
+impl<S: Data, T: Data> ListIter<(S, T)> for (S, Arc<VecDeque<T>>) {
+    fn for_each(&self, mut cb: impl FnMut(&(S, T), usize)) {
+        for (i, item) in self.1.iter().enumerate() {
+            let d = (self.0.clone(), item.to_owned());
+            cb(&d, i);
+        }
+    }
+
+    fn for_each_mut(&mut self, mut cb: impl FnMut(&mut (S, T), usize)) {
+        let mut new_data = VecDeque::with_capacity(self.1.len());
+        let mut any_shared_changed = false;
+        let mut any_el_changed = false;
+
+        for (i, item) in self.1.iter().enumerate() {
+            let mut d = (self.0.clone(), item.to_owned());
+            cb(&mut d, i);
+
+            if !any_shared_changed && !self.0.same(&d.0) {
+                any_shared_changed = true;
+            }
+            if any_shared_changed {
+                self.0 = d.0;
+            }
+            if !any_el_changed && !item.same(&d.1) {
+                any_el_changed = true;
+            }
+            new_data.push_back(d.1);
+        }
+
+        if any_el_changed {
+            self.1 = Arc::new(new_data);
+        }
+    }
+
+    fn data_len(&self) -> usize {
+        self.1.len()
+    }
+}
+
 impl<C: Data, T: ListIter<C>> Widget<T> for List<C> {
     fn event(&mut self, ctx: &mut EventCtx, event: &Event, data: &mut T, env: &Env) {
         let mut children = self.children.iter_mut();