Introduce VirtualMethods::attribute_mutated()

This replaces before_remove_attr(), after_remove_attr() and after_set_attr().
The virtual method takes the mutated attribute and an AttributeMutation value
to disambiguate between "attribute is changed", "attribute is added" and
"attribute is removed".

In the case of "attribute is changed", the mutation value contains a reference
to the old value of the mutated attribute, which is used to unregister outdated
named elements when the "id" attribute is changed on an element.

This greatly simplifies the handling of attributes, which in many cases don't
have any specific behaviour whether they are removed or changed or added. It
also fixes a few bugs where things were put in before_remove_attr() instead of
after_remove_attr() (e.g. when removing an href attribute from a base element).

A few helper functions in Element were also renamed and made private.

1 files changed, 18 insertions, 27 deletions

diff --git a/components/script/dom/htmlbuttonelement.rs b/components/script/dom/htmlbuttonelement.rs
index a8c95eb6d3b..c158ad36fb0 100644
--- a/components/script/dom/htmlbuttonelement.rs
+++ b/components/script/dom/htmlbuttonelement.rs
@@ -10,7 +10,7 @@ use dom::bindings::codegen::InheritTypes::{ElementCast, HTMLElementCast, HTMLBut
 use dom::bindings::codegen::InheritTypes::{HTMLButtonElementDerived, HTMLFieldSetElementDerived};
 use dom::bindings::js::Root;
 use dom::document::Document;
-use dom::element::{Element, ElementTypeId};
+use dom::element::{AttributeMutation, Element, ElementTypeId};
 use dom::event::Event;
 use dom::eventtarget::{EventTarget, EventTargetTypeId};
 use dom::htmlelement::{HTMLElement, HTMLElementTypeId};
@@ -56,7 +56,7 @@ impl HTMLButtonElement {
         HTMLButtonElement {
             htmlelement:
                 HTMLElement::new_inherited(HTMLElementTypeId::HTMLButtonElement, localName, prefix, document),
-            //TODO: implement button_type in after_set_attr
+            //TODO: implement button_type in attribute_mutated
             button_type: Cell::new(ButtonType::ButtonSubmit)
         }
     }
@@ -135,34 +135,25 @@ impl VirtualMethods for HTMLButtonElement {
         Some(htmlelement as &VirtualMethods)
     }
 
-    fn after_set_attr(&self, attr: &Attr) {
-        if let Some(ref s) = self.super_type() {
-            s.after_set_attr(attr);
-        }
-
-        match attr.local_name() {
-            &atom!("disabled") => {
-                let node = NodeCast::from_ref(self);
-                node.set_disabled_state(true);
-                node.set_enabled_state(false);
-            },
-            _ => ()
-        }
-    }
-
-    fn before_remove_attr(&self, attr: &Attr) {
-        if let Some(ref s) = self.super_type() {
-            s.before_remove_attr(attr);
-        }
-
+    fn attribute_mutated(&self, attr: &Attr, mutation: AttributeMutation) {
+        self.super_type().unwrap().attribute_mutated(attr, mutation);
         match attr.local_name() {
-            &atom!("disabled") => {
+            &atom!(disabled) => {
                 let node = NodeCast::from_ref(self);
-                node.set_disabled_state(false);
-                node.set_enabled_state(true);
-                node.check_ancestors_disabled_state_for_form_control();
+                match mutation {
+                    AttributeMutation::Set(Some(_)) => {}
+                    AttributeMutation::Set(None) => {
+                        node.set_disabled_state(true);
+                        node.set_enabled_state(false);
+                    },
+                    AttributeMutation::Removed => {
+                        node.set_disabled_state(false);
+                        node.set_enabled_state(true);
+                        node.check_ancestors_disabled_state_for_form_control();
+                    }
+                }
             },
-            _ => ()
+            _ => {},
         }
     }