Implement 'control' attribute for <label> elements

components/script/dom/htmllabelelement.rs

@@ -2,13 +2,18 @@
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
+use dom::attr::AttrValue;
 use dom::bindings::codegen::Bindings::HTMLLabelElementBinding;
 use dom::bindings::codegen::Bindings::HTMLLabelElementBinding::HTMLLabelElementMethods;
+use dom::bindings::conversions::Castable;
 use dom::bindings::js::Root;
 use dom::document::Document;
+use dom::element::Element;
 use dom::htmlelement::HTMLElement;
 use dom::htmlformelement::{FormControl, HTMLFormElement};
-use dom::node::Node;
+use dom::node::{document_from_node, Node};
+use dom::virtualmethods::VirtualMethods;
+use string_cache::Atom;
 use util::str::DOMString;
 
 #[dom_struct]
@@ -40,6 +45,48 @@ impl HTMLLabelElementMethods for HTMLLabelElement {
     fn GetForm(&self) -> Option<Root<HTMLFormElement>> {
         self.form_owner()
     }
+
+    // https://html.spec.whatwg.org/multipage/#dom-label-control
+    fn GetControl(&self) -> Option<Root<HTMLElement>> {
+        if !self.upcast::<Node>().is_in_doc() {
+            return None;
+        }
+
+        let for_attr = match self.upcast::<Element>().get_attribute(&ns!(""), &atom!("for")) {
+            Some(for_attr) => for_attr,
+            None => return self.first_labelable_descendant(),
+        };
+
+        let for_value = for_attr.value();
+        document_from_node(self).get_element_by_id(for_value.as_atom())
+                                .and_then(Root::downcast::<HTMLElement>)
+                                .into_iter()
+                                .filter(|e| e.is_labelable_element())
+                                .next()
+    }
+}
+
+impl VirtualMethods for HTMLLabelElement {
+    fn super_type(&self) -> Option<&VirtualMethods> {
+        Some(self.upcast::<HTMLElement>() as &VirtualMethods)
+    }
+
+    fn parse_plain_attribute(&self, name: &Atom, value: DOMString) -> AttrValue {
+        match name {
+            &atom!("for") => AttrValue::from_atomic(value),
+            _ => self.super_type().unwrap().parse_plain_attribute(name, value),
+        }
+    }
+}
+
+impl HTMLLabelElement {
+    fn first_labelable_descendant(&self) -> Option<Root<HTMLElement>> {
+        self.upcast::<Node>()
+            .traverse_preorder()
+            .filter_map(Root::downcast::<HTMLElement>)
+            .filter(|elem| elem.is_labelable_element())
+            .next()
+    }
 }
 
 impl FormControl for HTMLLabelElement {}