RadioNodeList now reflects changes to the parent, but has room for performance optimization

components/script/dom/nodelist.rs

@@ -7,7 +7,9 @@ use crate::dom::bindings::codegen::Bindings::NodeListBinding;
 use crate::dom::bindings::codegen::Bindings::NodeListBinding::NodeListMethods;
 use crate::dom::bindings::reflector::{reflect_dom_object, Reflector};
 use crate::dom::bindings::root::{Dom, DomRoot, MutNullableDom};
+use crate::dom::bindings::str::DOMString;
 use crate::dom::htmlelement::HTMLElement;
+use crate::dom::htmlformelement::HTMLFormElement;
 use crate::dom::node::{ChildrenMutation, Node};
 use crate::dom::window::Window;
 use dom_struct::dom_struct;
@@ -19,6 +21,7 @@ pub enum NodeListType {
     Simple(Vec<Dom<Node>>),
     Children(ChildrenList),
     Labels(LabelsList),
+    Radio(RadioList),
 }
 
 // https://dom.spec.whatwg.org/#interface-nodelist
@@ -83,6 +86,7 @@ impl NodeListMethods for NodeList {
             NodeListType::Simple(ref elems) => elems.len() as u32,
             NodeListType::Children(ref list) => list.len(),
             NodeListType::Labels(ref list) => list.len(),
+            NodeListType::Radio(ref list) => list.len(),
         }
     }
 
@@ -94,6 +98,7 @@ impl NodeListMethods for NodeList {
                 .map(|node| DomRoot::from_ref(&**node)),
             NodeListType::Children(ref list) => list.item(index),
             NodeListType::Labels(ref list) => list.item(index),
+            NodeListType::Radio(ref list) => list.item(index),
         }
     }
 
@@ -108,20 +113,22 @@ impl NodeList {
         if let NodeListType::Children(ref list) = self.list_type {
             list
         } else {
-            panic!("called as_children_list() on a simple node list")
+            panic!("called as_children_list() on a non-children node list")
         }
     }
 
-    pub fn as_simple_list(&self) -> &Vec<Dom<Node>> {
-        if let NodeListType::Simple(ref list) = self.list_type {
+    pub fn as_radio_list(&self) -> &RadioList {
+        if let NodeListType::Radio(ref list) = self.list_type {
             list
         } else {
-            panic!("called as_simple_list() on a children node list")
+            panic!("called as_radio_list() on a non-radio node list")
         }
     }
 
     pub fn iter<'a>(&'a self) -> impl Iterator<Item = DomRoot<Node>> + 'a {
         let len = self.Length();
+        // There is room for optimization here in non-simple cases,
+        // as calling Item repeatedly on a live list can involve redundant work.
         (0..len).flat_map(move |i| self.Item(i))
     }
 }
@@ -328,7 +335,7 @@ impl ChildrenList {
     }
 }
 
-// Labels lists: There might room for performance optimization
+// Labels lists: There might be room for performance optimization
 // analogous to the ChildrenMutation case of a children list,
 // in which we can keep information from an older access live
 // if we know nothing has happened that would change it.
@@ -357,3 +364,40 @@ impl LabelsList {
         self.element.label_at(index)
     }
 }
+
+// Radio node lists: There is room for performance improvement here;
+// a form is already aware of changes to its set of controls,
+// so a radio list can cache and cache-invalidate its contents
+// just by hooking into what the form already knows without a
+// separate mutation observer. FIXME #25482
+#[derive(Clone, Copy, JSTraceable, MallocSizeOf)]
+pub enum RadioListMode {
+    ControlsExceptImageInputs,
+    Images,
+}
+
+#[derive(JSTraceable, MallocSizeOf)]
+#[unrooted_must_root_lint::must_root]
+pub struct RadioList {
+    form: Dom<HTMLFormElement>,
+    mode: RadioListMode,
+    name: DOMString,
+}
+
+impl RadioList {
+    pub fn new(form: &HTMLFormElement, mode: RadioListMode, name: DOMString) -> RadioList {
+        RadioList {
+            form: Dom::from_ref(form),
+            mode: mode,
+            name: name,
+        }
+    }
+
+    pub fn len(&self) -> u32 {
+        self.form.count_for_radio_list(self.mode, &self.name)
+    }
+
+    pub fn item(&self, index: u32) -> Option<DomRoot<Node>> {
+        self.form.nth_for_radio_list(index, self.mode, &self.name)
+    }
+}