Implement 'control' attribute for <label> elements

5 files changed, 74 insertions, 3 deletions

diff --git a/components/script/dom/document.rs b/components/script/dom/document.rs
index 23d455a1903..771342d0f36 100644
--- a/components/script/dom/document.rs
+++ b/components/script/dom/document.rs
@@ -1147,7 +1147,7 @@ impl Document {
         })
     }
 
-    fn get_element_by_id(&self, id: &Atom) -> Option<Root<Element>> {
+    pub fn get_element_by_id(&self, id: &Atom) -> Option<Root<Element>> {
         self.idmap.borrow().get(&id).map(|ref elements| (*elements)[0].root())
     }
 }
diff --git a/components/script/dom/htmlelement.rs b/components/script/dom/htmlelement.rs
index 34a7847187a..b04082eae4d 100644
--- a/components/script/dom/htmlelement.rs
+++ b/components/script/dom/htmlelement.rs
@@ -296,6 +296,26 @@ impl HTMLElement {
         let local_name = Atom::from_slice(&to_snake_case(local_name));
         self.upcast::<Element>().remove_attribute(&ns!(""), &local_name);
     }
+
+    // https://html.spec.whatwg.org/multipage/#category-label
+    pub fn is_labelable_element(&self) -> bool {
+        // Note: HTMLKeygenElement is omitted because Servo doesn't currently implement it
+        match self.upcast::<Node>().type_id() {
+            NodeTypeId::Element(ElementTypeId::HTMLElement(type_id)) =>
+                match type_id {
+                    HTMLElementTypeId::HTMLInputElement =>
+                        self.downcast::<HTMLInputElement>().unwrap().Type() != "hidden",
+                    HTMLElementTypeId::HTMLButtonElement |
+                        HTMLElementTypeId::HTMLMeterElement |
+                        HTMLElementTypeId::HTMLOutputElement |
+                        HTMLElementTypeId::HTMLProgressElement |
+                        HTMLElementTypeId::HTMLSelectElement |
+                        HTMLElementTypeId::HTMLTextAreaElement => true,
+                    _ => false,
+                },
+            _ => false,
+        }
+    }
 }
 
 impl VirtualMethods for HTMLElement {
diff --git a/components/script/dom/htmllabelelement.rs b/components/script/dom/htmllabelelement.rs
index 3beefc3db9a..e3328648c4d 100644
--- a/components/script/dom/htmllabelelement.rs
+++ b/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 {}
diff --git a/components/script/dom/virtualmethods.rs b/components/script/dom/virtualmethods.rs
index da80f414da4..32406205e5d 100644
--- a/components/script/dom/virtualmethods.rs
+++ b/components/script/dom/virtualmethods.rs
@@ -25,6 +25,7 @@ use dom::htmlheadelement::HTMLHeadElement;
 use dom::htmliframeelement::HTMLIFrameElement;
 use dom::htmlimageelement::HTMLImageElement;
 use dom::htmlinputelement::HTMLInputElement;
+use dom::htmllabelelement::HTMLLabelElement;
 use dom::htmllinkelement::HTMLLinkElement;
 use dom::htmlmetaelement::HTMLMetaElement;
 use dom::htmlobjectelement::HTMLObjectElement;
@@ -164,6 +165,9 @@ pub fn vtable_for(node: &Node) -> &VirtualMethods {
         NodeTypeId::Element(ElementTypeId::HTMLElement(HTMLElementTypeId::HTMLInputElement)) => {
             node.downcast::<HTMLInputElement>().unwrap() as &VirtualMethods
         }
+        NodeTypeId::Element(ElementTypeId::HTMLElement(HTMLElementTypeId::HTMLLabelElement)) => {
+            node.downcast::<HTMLLabelElement>().unwrap() as &VirtualMethods
+        }
         NodeTypeId::Element(ElementTypeId::HTMLElement(HTMLElementTypeId::HTMLLinkElement)) => {
             node.downcast::<HTMLLinkElement>().unwrap() as &VirtualMethods
         }
diff --git a/components/script/dom/webidls/HTMLLabelElement.webidl b/components/script/dom/webidls/HTMLLabelElement.webidl
index 00900df77fc..7188f1d2d43 100644
--- a/components/script/dom/webidls/HTMLLabelElement.webidl
+++ b/components/script/dom/webidls/HTMLLabelElement.webidl
@@ -7,5 +7,5 @@
 interface HTMLLabelElement : HTMLElement {
   readonly attribute HTMLFormElement? form;
   //         attribute DOMString htmlFor;
-  //readonly attribute HTMLElement? control;
+  readonly attribute HTMLElement? control;
 };