auto merge of #4133 : mttr/servo/form_resetting, r=jdm

We can reset `<input type=text>` fields! I wish I could've done something with checkboxes, but unfortunately, that's it for now.

In addition to that, this PR implements `HTMLInputAttribute.defaultValue`, updates wpt-test to expect passing tests as a result of that implementation, and fixes an index error crash with text inputs.

edit: also includes an html example where one may lazily watch form resets in action: ` tests/html/form_reset_handsfree.html`

8 files changed, 257 insertions, 54 deletions

diff --git a/components/script/dom/element.rs b/components/script/dom/element.rs
index c3c0b9fcb28..a8beed315fe 100644
--- a/components/script/dom/element.rs
+++ b/components/script/dom/element.rs
@@ -35,7 +35,7 @@ use dom::event::Event;
 use dom::eventtarget::{EventTarget, NodeTargetTypeId, EventTargetHelpers};
 use dom::htmlbodyelement::{HTMLBodyElement, HTMLBodyElementHelpers};
 use dom::htmlcollection::HTMLCollection;
-use dom::htmlinputelement::{HTMLInputElement, RawLayoutHTMLInputElementHelpers};
+use dom::htmlinputelement::{HTMLInputElement, RawLayoutHTMLInputElementHelpers, HTMLInputElementHelpers};
 use dom::htmlserializer::serialize;
 use dom::htmltableelement::{HTMLTableElement, HTMLTableElementHelpers};
 use dom::htmltablecellelement::{HTMLTableCellElement, HTMLTableCellElementHelpers};
@@ -212,6 +212,7 @@ pub trait RawLayoutElementHelpers {
     unsafe fn get_integer_attribute_for_layout(&self, integer_attribute: IntegerAttribute)
                                                -> Option<i32>;
     unsafe fn get_checked_state_for_layout(&self) -> bool;
+    unsafe fn get_indeterminate_state_for_layout(&self) -> bool;
     unsafe fn get_unsigned_integer_attribute_for_layout(&self, attribute: UnsignedIntegerAttribute)
                                                         -> Option<u32>;
     unsafe fn get_simple_color_attribute_for_layout(&self, attribute: SimpleColorAttribute)
@@ -352,6 +353,18 @@ impl RawLayoutElementHelpers for Element {
         this.get_checked_state_for_layout()
     }
 
+    #[inline]
+    #[allow(unrooted_must_root)]
+    unsafe fn get_indeterminate_state_for_layout(&self) -> bool {
+        // TODO progress elements can also be matched with :indeterminate
+        if !self.is_htmlinputelement() {
+            return false
+        }
+        let this: &HTMLInputElement = mem::transmute(self);
+        this.get_indeterminate_state_for_layout()
+    }
+
+
     unsafe fn get_unsigned_integer_attribute_for_layout(&self,
                                                         attribute: UnsignedIntegerAttribute)
                                                         -> Option<u32> {
@@ -1289,6 +1302,12 @@ impl<'a> style::TElement<'a> for JSRef<'a, Element> {
             None => false,
         }
     }
+    fn get_indeterminate_state(self) -> bool {
+        match HTMLInputElementCast::to_ref(self) {
+            Some(input) => input.get_indeterminate_state(),
+            None => false,
+        }
+    }
     fn has_class(self, name: &Atom) -> bool {
         // FIXME(zwarich): Remove this when UFCS lands and there is a better way
         // of disambiguating methods.
diff --git a/components/script/dom/htmlformelement.rs b/components/script/dom/htmlformelement.rs
index 1d12bdebf39..62f5e3aa62e 100644
--- a/components/script/dom/htmlformelement.rs
+++ b/components/script/dom/htmlformelement.rs
@@ -2,23 +2,26 @@
  * 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::bindings::codegen::Bindings::DocumentBinding::DocumentMethods;
 use dom::bindings::codegen::Bindings::EventBinding::EventMethods;
 use dom::bindings::codegen::Bindings::EventTargetBinding::EventTargetMethods;
 use dom::bindings::codegen::Bindings::HTMLFormElementBinding;
 use dom::bindings::codegen::Bindings::HTMLFormElementBinding::HTMLFormElementMethods;
 use dom::bindings::codegen::Bindings::HTMLInputElementBinding::HTMLInputElementMethods;
 use dom::bindings::codegen::InheritTypes::{EventTargetCast, HTMLFormElementDerived, NodeCast};
-use dom::bindings::codegen::InheritTypes::HTMLInputElementCast;
+use dom::bindings::codegen::InheritTypes::{HTMLInputElementCast, HTMLTextAreaElementCast, HTMLFormElementCast};
 use dom::bindings::global::Window;
-use dom::bindings::js::{JSRef, Temporary};
+use dom::bindings::js::{JSRef, Temporary, OptionalRootable};
 use dom::bindings::utils::{Reflectable, Reflector};
 use dom::document::{Document, DocumentHelpers};
 use dom::element::{Element, AttributeHandlers, HTMLFormElementTypeId, HTMLTextAreaElementTypeId, HTMLDataListElementTypeId};
 use dom::element::{HTMLInputElementTypeId, HTMLButtonElementTypeId, HTMLObjectElementTypeId, HTMLSelectElementTypeId};
+use dom::element::{HTMLOutputElementTypeId};
 use dom::event::{Event, EventHelpers, Bubbles, Cancelable};
 use dom::eventtarget::{EventTarget, NodeTargetTypeId};
 use dom::htmlelement::HTMLElement;
 use dom::htmlinputelement::HTMLInputElement;
+use dom::htmltextareaelement::HTMLTextAreaElement;
 use dom::node::{Node, NodeHelpers, ElementNodeTypeId, document_from_node, window_from_node};
 use hyper::method::Post;
 use servo_msg::constellation_msg::LoadData;
@@ -29,9 +32,12 @@ use url::UrlParser;
 use url::form_urlencoded::serialize;
 use string_cache::Atom;
 
+use std::cell::Cell;
+
 #[dom_struct]
 pub struct HTMLFormElement {
     htmlelement: HTMLElement,
+    marked_for_reset: Cell<bool>,
 }
 
 impl HTMLFormElementDerived for EventTarget {
@@ -43,7 +49,8 @@ impl HTMLFormElementDerived for EventTarget {
 impl HTMLFormElement {
     fn new_inherited(localName: DOMString, prefix: Option<DOMString>, document: JSRef<Document>) -> HTMLFormElement {
         HTMLFormElement {
-            htmlelement: HTMLElement::new_inherited(HTMLFormElementTypeId, localName, prefix, document)
+            htmlelement: HTMLElement::new_inherited(HTMLFormElementTypeId, localName, prefix, document),
+            marked_for_reset: Cell::new(false),
         }
     }
 
@@ -117,6 +124,11 @@ impl<'a> HTMLFormElementMethods for JSRef<'a, HTMLFormElement> {
     fn Submit(self) {
         self.submit(FromFormSubmitMethod, FormElement(self));
     }
+
+    // https://html.spec.whatwg.org/multipage/forms.html#dom-form-reset
+    fn Reset(self) {
+        self.reset(FromFormResetMethod);
+    }
 }
 
 pub enum SubmittedFrom {
@@ -124,11 +136,18 @@ pub enum SubmittedFrom {
     NotFromFormSubmitMethod
 }
 
+pub enum ResetFrom {
+    FromFormResetMethod,
+    NotFromFormResetMethod
+}
+
 pub trait HTMLFormElementHelpers {
     // https://html.spec.whatwg.org/multipage/forms.html#concept-form-submit
     fn submit(self, submit_method_flag: SubmittedFrom, submitter: FormSubmitter);
     // https://html.spec.whatwg.org/multipage/forms.html#constructing-the-form-data-set
     fn get_form_dataset(self, submitter: Option<FormSubmitter>) -> Vec<FormDatum>;
+    // https://html.spec.whatwg.org/multipage/forms.html#dom-form-reset
+    fn reset(self, submit_method_flag: ResetFrom);
 }
 
 impl<'a> HTMLFormElementHelpers for JSRef<'a, HTMLFormElement> {
@@ -316,6 +335,59 @@ impl<'a> HTMLFormElementHelpers for JSRef<'a, HTMLFormElement> {
         };
         ret
     }
+
+    fn reset(self, _reset_method_flag: ResetFrom) {
+        // https://html.spec.whatwg.org/multipage/forms.html#locked-for-reset
+        if self.marked_for_reset.get() {
+            return;
+        } else {
+            self.marked_for_reset.set(true);
+        }
+
+        let win = window_from_node(self).root();
+        let event = Event::new(Window(*win),
+                               "reset".to_string(),
+                               Bubbles, Cancelable).root();
+        let target: JSRef<EventTarget> = EventTargetCast::from_ref(self);
+        target.DispatchEvent(*event).ok();
+        if event.DefaultPrevented() {
+            return;
+        }
+
+        let node: JSRef<Node> = NodeCast::from_ref(self);
+
+        // TODO: This is an incorrect way of getting controls owned
+        //       by the form, but good enough until html5ever lands
+        for child in node.traverse_preorder() {
+            match child.type_id() {
+                ElementNodeTypeId(HTMLInputElementTypeId) => {
+                    let input: JSRef<HTMLInputElement> = HTMLInputElementCast::to_ref(child)
+                                                                               .unwrap();
+                    input.reset()
+                }
+                // TODO HTMLKeygenElement unimplemented
+                //ElementNodeTypeID(HTMLKeygenElementTypeId) => {
+                //    // Unimplemented
+                //    {}
+                //}
+                ElementNodeTypeId(HTMLSelectElementTypeId) => {
+                    // Unimplemented
+                    {}
+                }
+                ElementNodeTypeId(HTMLTextAreaElementTypeId) => {
+                    let textarea: JSRef<HTMLTextAreaElement> = HTMLTextAreaElementCast::to_ref(child)
+                                                                                        .unwrap();
+                    textarea.reset()
+                }
+                ElementNodeTypeId(HTMLOutputElementTypeId) => {
+                    // Unimplemented
+                    {}
+                }
+                _ => {}
+            }
+        };
+        self.marked_for_reset.set(false);
+    }
 }
 
 impl Reflectable for HTMLFormElement {
@@ -412,7 +484,30 @@ impl<'a> FormSubmitter<'a> {
 }
 
 pub trait FormControl<'a> : Copy {
-    fn form_owner(self) -> Option<Temporary<HTMLFormElement>>;
+    // FIXME: This is wrong (https://github.com/servo/servo/issues/3553)
+    //        but we need html5ever to do it correctly
+    fn form_owner(self) -> Option<Temporary<HTMLFormElement>> {
+        // https://html.spec.whatwg.org/multipage/forms.html#reset-the-form-owner
+        let elem = self.to_element();
+        let owner = elem.get_string_attribute(&atom!("form"));
+        if !owner.is_empty() {
+            let doc = document_from_node(elem).root();
+            let owner = doc.GetElementById(owner).root();
+            match owner {
+                Some(o) => {
+                    let maybe_form: Option<JSRef<HTMLFormElement>> = HTMLFormElementCast::to_ref(*o);
+                    if maybe_form.is_some() {
+                        return maybe_form.map(Temporary::from_rooted);
+                    }
+                },
+                _ => ()
+            }
+        }
+        let node: JSRef<Node> = NodeCast::from_ref(elem);
+        node.ancestors().filter_map(|a| HTMLFormElementCast::to_ref(a)).next()
+            .map(Temporary::from_rooted)
+    }
+
     fn get_form_attribute(self,
                           attr: &Atom,
                           input: |Self| -> DOMString,
@@ -426,4 +521,5 @@ pub trait FormControl<'a> : Copy {
     fn to_element(self) -> JSRef<'a, Element>;
     // https://html.spec.whatwg.org/multipage/forms.html#concept-fe-mutable
     fn mutable(self) -> bool;
+    fn reset(self);
 }
diff --git a/components/script/dom/htmlinputelement.rs b/components/script/dom/htmlinputelement.rs
index 5b0133395a7..3ea2a38a686 100644
--- a/components/script/dom/htmlinputelement.rs
+++ b/components/script/dom/htmlinputelement.rs
@@ -7,12 +7,11 @@ use dom::attr::{Attr, AttrValue, UIntAttrValue};
 use dom::attr::AttrHelpers;
 use dom::bindings::cell::DOMRefCell;
 use dom::bindings::codegen::Bindings::AttrBinding::AttrMethods;
-use dom::bindings::codegen::Bindings::DocumentBinding::DocumentMethods;
 use dom::bindings::codegen::Bindings::EventBinding::EventMethods;
 use dom::bindings::codegen::Bindings::EventTargetBinding::EventTargetMethods;
 use dom::bindings::codegen::Bindings::HTMLInputElementBinding;
 use dom::bindings::codegen::Bindings::HTMLInputElementBinding::HTMLInputElementMethods;
-use dom::bindings::codegen::InheritTypes::{ElementCast, HTMLElementCast, HTMLFormElementCast, HTMLInputElementCast, NodeCast};
+use dom::bindings::codegen::InheritTypes::{ElementCast, HTMLElementCast, HTMLInputElementCast, NodeCast};
 use dom::bindings::codegen::InheritTypes::{HTMLInputElementDerived, HTMLFieldSetElementDerived, EventTargetCast};
 use dom::bindings::codegen::InheritTypes::KeyboardEventCast;
 use dom::bindings::global::Window;
@@ -27,7 +26,7 @@ use dom::eventtarget::{EventTarget, NodeTargetTypeId};
 use dom::htmlelement::HTMLElement;
 use dom::keyboardevent::KeyboardEvent;
 use dom::htmlformelement::{InputElement, FormControl, HTMLFormElement, HTMLFormElementHelpers};
-use dom::htmlformelement::{NotFromFormSubmitMethod};
+use dom::htmlformelement::{NotFromFormSubmitMethod, NotFromFormResetMethod};
 use dom::node::{DisabledStateHelpers, Node, NodeHelpers, ElementNodeTypeId, OtherNodeDamage};
 use dom::node::{document_from_node, window_from_node};
 use dom::virtualmethods::VirtualMethods;
@@ -63,7 +62,9 @@ pub struct HTMLInputElement {
     htmlelement: HTMLElement,
     input_type: Cell<InputType>,
     checked: Cell<bool>,
+    checked_changed: Cell<bool>,
     indeterminate: Cell<bool>,
+    value_changed: Cell<bool>,
     size: Cell<u32>,
     textinput: DOMRefCell<TextInput>,
     activation_state: DOMRefCell<InputActivationState>,
@@ -74,6 +75,7 @@ pub struct HTMLInputElement {
 struct InputActivationState {
     indeterminate: bool,
     checked: bool,
+    checked_changed: bool,
     checked_radio: MutNullableJS<HTMLInputElement>,
     // In case mutability changed
     was_mutable: bool,
@@ -86,6 +88,7 @@ impl InputActivationState {
         InputActivationState {
             indeterminate: false,
             checked: false,
+            checked_changed: false,
             checked_radio: Default::default(),
             was_mutable: false,
             old_type: InputText
@@ -108,6 +111,8 @@ impl HTMLInputElement {
             input_type: Cell::new(InputText),
             checked: Cell::new(false),
             indeterminate: Cell::new(false),
+            checked_changed: Cell::new(false),
+            value_changed: Cell::new(false),
             size: Cell::new(DEFAULT_INPUT_SIZE),
             textinput: DOMRefCell::new(TextInput::new(Single, "".to_string())),
             activation_state: DOMRefCell::new(InputActivationState::new())
@@ -128,6 +133,7 @@ pub trait LayoutHTMLInputElementHelpers {
 
 pub trait RawLayoutHTMLInputElementHelpers {
     unsafe fn get_checked_state_for_layout(&self) -> bool;
+    unsafe fn get_indeterminate_state_for_layout(&self) -> bool;
     unsafe fn get_size_for_layout(&self) -> u32;
 }
 
@@ -171,6 +177,11 @@ impl RawLayoutHTMLInputElementHelpers for HTMLInputElement {
     }
 
     #[allow(unrooted_must_root)]
+    unsafe fn get_indeterminate_state_for_layout(&self) -> bool {
+        self.indeterminate.get()
+    }
+
+    #[allow(unrooted_must_root)]
     unsafe fn get_size_for_layout(&self) -> u32 {
         self.size.get()
     }
@@ -183,6 +194,12 @@ impl<'a> HTMLInputElementMethods for JSRef<'a, HTMLInputElement> {
     // http://www.whatwg.org/html/#dom-fe-disabled
     make_bool_setter!(SetDisabled, "disabled")
 
+    // https://html.spec.whatwg.org/multipage/forms.html#dom-input-defaultchecked
+    make_bool_getter!(DefaultChecked, "checked")
+
+    // https://html.spec.whatwg.org/multipage/forms.html#dom-input-defaultchecked
+    make_bool_setter!(SetDefaultChecked, "checked")
+
     // https://html.spec.whatwg.org/multipage/forms.html#dom-input-checked
     fn Checked(self) -> bool {
         self.checked.get()
@@ -190,7 +207,7 @@ impl<'a> HTMLInputElementMethods for JSRef<'a, HTMLInputElement> {
 
     // https://html.spec.whatwg.org/multipage/forms.html#dom-input-checked
     fn SetChecked(self, checked: bool) {
-        self.update_checked_state(checked);
+        self.update_checked_state(checked, true);
     }
 
     // https://html.spec.whatwg.org/multipage/forms.html#dom-input-readonly
@@ -223,7 +240,17 @@ impl<'a> HTMLInputElementMethods for JSRef<'a, HTMLInputElement> {
     }
 
     // https://html.spec.whatwg.org/multipage/forms.html#dom-input-value
-    make_setter!(SetValue, "value")
+    fn SetValue(self, value: DOMString) {
+        self.textinput.borrow_mut().set_content(value);
+        self.value_changed.set(true);
+        self.force_relayout();
+    }
+
+    // https://html.spec.whatwg.org/multipage/forms.html#dom-input-defaultvalue
+    make_getter!(DefaultValue, "value")
+
+    // https://html.spec.whatwg.org/multipage/forms.html#dom-input-defaultvalue
+    make_setter!(SetDefaultValue, "value")
 
     // https://html.spec.whatwg.org/multipage/forms.html#attr-fe-name
     make_getter!(Name)
@@ -262,7 +289,6 @@ impl<'a> HTMLInputElementMethods for JSRef<'a, HTMLInputElement> {
 
     // https://html.spec.whatwg.org/multipage/forms.html#dom-input-indeterminate
     fn SetIndeterminate(self, val: bool) {
-        // FIXME #4079 this should change the appearance
         self.indeterminate.set(val)
     }
 }
@@ -271,8 +297,9 @@ pub trait HTMLInputElementHelpers {
     fn force_relayout(self);
     fn radio_group_updated(self, group: Option<&str>);
     fn get_radio_group_name(self) -> Option<String>;
-    fn update_checked_state(self, checked: bool);
+    fn update_checked_state(self, checked: bool, dirty: bool);
     fn get_size(&self) -> u32;
+    fn get_indeterminate_state(self) -> bool;
 }
 
 fn broadcast_radio_checked(broadcaster: JSRef<HTMLInputElement>, group: Option<&str>) {
@@ -331,8 +358,13 @@ impl<'a> HTMLInputElementHelpers for JSRef<'a, HTMLInputElement> {
             .map(|name| name.Value())
     }
 
-    fn update_checked_state(self, checked: bool) {
+    fn update_checked_state(self, checked: bool, dirty: bool) {
         self.checked.set(checked);
+
+        if dirty {
+            self.checked_changed.set(true);
+        }
+
         if self.input_type.get() == InputRadio && checked {
             broadcast_radio_checked(self,
                                     self.get_radio_group_name()
@@ -346,6 +378,10 @@ impl<'a> HTMLInputElementHelpers for JSRef<'a, HTMLInputElement> {
     fn get_size(&self) -> u32 {
         self.size.get()
     }
+
+    fn get_indeterminate_state(self) -> bool {
+        self.indeterminate.get()
+    }
 }
 
 impl<'a> VirtualMethods for JSRef<'a, HTMLInputElement> {
@@ -367,7 +403,10 @@ impl<'a> VirtualMethods for JSRef<'a, HTMLInputElement> {
                 node.set_enabled_state(false);
             }
             &atom!("checked") => {
-                self.update_checked_state(true);
+                // https://html.spec.whatwg.org/multipage/forms.html#the-input-element:concept-input-checked-dirty
+                if !self.checked_changed.get() {
+                    self.update_checked_state(true, false);
+                }
             }
             &atom!("size") => {
                 match *attr.value() {
@@ -396,8 +435,10 @@ impl<'a> VirtualMethods for JSRef<'a, HTMLInputElement> {
                 self.force_relayout();
             }
             &atom!("value") => {
-                self.textinput.borrow_mut().set_content(attr.value().as_slice().to_string());
-                self.force_relayout();
+                if !self.value_changed.get() {
+                    self.textinput.borrow_mut().set_content(attr.value().as_slice().to_string());
+                    self.force_relayout();
+                }
             }
             &atom!("name") => {
                 if self.input_type.get() == InputRadio {
@@ -423,7 +464,10 @@ impl<'a> VirtualMethods for JSRef<'a, HTMLInputElement> {
                 node.check_ancestors_disabled_state_for_form_control();
             }
             &atom!("checked") => {
-                self.update_checked_state(false);
+                // https://html.spec.whatwg.org/multipage/forms.html#the-input-element:concept-input-checked-dirty
+                if !self.checked_changed.get() {
+                    self.update_checked_state(false, false);
+                }
             }
             &atom!("size") => {
                 self.size.set(DEFAULT_INPUT_SIZE);
@@ -440,8 +484,10 @@ impl<'a> VirtualMethods for JSRef<'a, HTMLInputElement> {
                 self.force_relayout();
             }
             &atom!("value") => {
-                self.textinput.borrow_mut().set_content("".to_string());
-                self.force_relayout();
+                if !self.value_changed.get() {
+                    self.textinput.borrow_mut().set_content("".to_string());
+                    self.force_relayout();
+                }
             }
             &atom!("name") => {
                 if self.input_type.get() == InputRadio {
@@ -493,7 +539,7 @@ impl<'a> VirtualMethods for JSRef<'a, HTMLInputElement> {
 
         if "click" == event.Type().as_slice() && !event.DefaultPrevented() {
             match self.input_type.get() {
-                InputRadio => self.SetChecked(true),
+                InputRadio => self.update_checked_state(true, true),
                 _ => {}
             }
 
@@ -511,6 +557,7 @@ impl<'a> VirtualMethods for JSRef<'a, HTMLInputElement> {
                     match self.textinput.borrow_mut().handle_keydown(keyevent) {
                         TriggerDefaultAction => (),
                         DispatchInput => {
+                            self.value_changed.set(true);
                             self.force_relayout();
                             event.PreventDefault();
                         }
@@ -528,30 +575,6 @@ impl Reflectable for HTMLInputElement {
 }
 
 impl<'a> FormControl<'a> for JSRef<'a, HTMLInputElement> {
-    // FIXME: This is wrong (https://github.com/servo/servo/issues/3553)
-    //        but we need html5ever to do it correctly
-    fn form_owner(self) -> Option<Temporary<HTMLFormElement>> {
-        // https://html.spec.whatwg.org/multipage/forms.html#reset-the-form-owner
-        let elem: JSRef<Element> = ElementCast::from_ref(self);
-        let owner = elem.get_string_attribute(&atom!("form"));
-        if !owner.is_empty() {
-            let doc = document_from_node(self).root();
-            let owner = doc.GetElementById(owner).root();
-            match owner {
-                Some(o) => {
-                    let maybe_form: Option<JSRef<HTMLFormElement>> = HTMLFormElementCast::to_ref(*o);
-                    if maybe_form.is_some() {
-                        return maybe_form.map(Temporary::from_rooted);
-                    }
-                },
-                _ => ()
-            }
-        }
-        let node: JSRef<Node> = NodeCast::from_ref(self);
-        node.ancestors().filter_map(|a| HTMLFormElementCast::to_ref(a)).next()
-            .map(Temporary::from_rooted)
-    }
-
     fn to_element(self) -> JSRef<'a, Element> {
         ElementCast::from_ref(self)
     }
@@ -562,6 +585,21 @@ impl<'a> FormControl<'a> for JSRef<'a, HTMLInputElement> {
         // https://html.spec.whatwg.org/multipage/forms.html#the-readonly-attribute:concept-fe-mutable
         !(self.Disabled() || self.ReadOnly())
     }
+
+    // https://html.spec.whatwg.org/multipage/forms.html#the-input-element:concept-form-reset-control
+    fn reset(self) {
+        match self.input_type.get() {
+            InputRadio | InputCheckbox => {
+                self.update_checked_state(self.DefaultChecked(), false);
+                self.checked_changed.set(false);
+            },
+            InputImage => (),
+            _ => ()
+        }
+
+        self.SetValue(self.DefaultValue());
+        self.value_changed.set(false);
+    }
 }
 
 
@@ -580,12 +618,15 @@ impl<'a> Activatable for JSRef<'a, HTMLInputElement> {
             match ty {
                 // https://html.spec.whatwg.org/multipage/forms.html#submit-button-state-(type=submit):activation-behavior
                 // InputSubmit => (), // No behavior defined
+                // https://html.spec.whatwg.org/multipage/forms.html#reset-button-state-(type=reset):activation-behavior
+                // InputSubmit => (), // No behavior defined
                 InputCheckbox => {
                     // https://html.spec.whatwg.org/multipage/forms.html#checkbox-state-(type=checkbox):pre-click-activation-steps
                     // cache current values of `checked` and `indeterminate`
                     // we may need to restore them later
                     cache.indeterminate = self.Indeterminate();
                     cache.checked = self.Checked();
+                    cache.checked_changed = self.checked_changed.get();
                     self.SetIndeterminate(false);
                     self.SetChecked(!cache.checked);
                 },
@@ -606,6 +647,7 @@ impl<'a> Activatable for JSRef<'a, HTMLInputElement> {
                                 .find(|r| r.Checked())
                     };
                     cache.checked_radio.assign(checked_member);
+                    cache.checked_changed = self.checked_changed.get();
                     self.SetChecked(true);
                 }
                 _ => ()
@@ -625,12 +667,15 @@ impl<'a> Activatable for JSRef<'a, HTMLInputElement> {
         match ty {
             // https://html.spec.whatwg.org/multipage/forms.html#submit-button-state-(type=submit):activation-behavior
             // InputSubmit => (), // No behavior defined
+            // https://html.spec.whatwg.org/multipage/forms.html#reset-button-state-(type=reset):activation-behavior
+            // InputReset => (), // No behavior defined
             // https://html.spec.whatwg.org/multipage/forms.html#checkbox-state-(type=checkbox):canceled-activation-steps
             InputCheckbox => {
                 // We want to restore state only if the element had been changed in the first place
                 if cache.was_mutable {
                     self.SetIndeterminate(cache.indeterminate);
                     self.SetChecked(cache.checked);
+                    self.checked_changed.set(cache.checked_changed);
                 }
             },
             // https://html.spec.whatwg.org/multipage/forms.html#radio-button-state-(type=radio):canceled-activation-steps
@@ -654,6 +699,7 @@ impl<'a> Activatable for JSRef<'a, HTMLInputElement> {
                         },
                         None => self.SetChecked(false)
                     };
+                    self.checked_changed.set(cache.checked_changed);
                 }
             }
             _ => ()
@@ -678,6 +724,15 @@ impl<'a> Activatable for JSRef<'a, HTMLInputElement> {
                     });
                 }
             },
+            InputReset => {
+                // https://html.spec.whatwg.org/multipage/forms.html#reset-button-state-(type=reset):activation-behavior
+                // FIXME (Manishearth): support document owners (needs ability to get parent browsing context)
+                if self.mutable() /* and document owner is fully active */ {
+                    self.form_owner().map(|o| {
+                        o.root().reset(NotFromFormResetMethod)
+                    });
+                }
+            },
             InputCheckbox | InputRadio => {
                 // https://html.spec.whatwg.org/multipage/forms.html#checkbox-state-(type=checkbox):activation-behavior
                 // https://html.spec.whatwg.org/multipage/forms.html#radio-button-state-(type=radio):activation-behavior
diff --git a/components/script/dom/htmltextareaelement.rs b/components/script/dom/htmltextareaelement.rs
index 642feb38b93..969454afc86 100644
--- a/components/script/dom/htmltextareaelement.rs
+++ b/components/script/dom/htmltextareaelement.rs
@@ -12,13 +12,14 @@ use dom::bindings::codegen::Bindings::NodeBinding::NodeMethods;
 use dom::bindings::codegen::InheritTypes::{ElementCast, HTMLElementCast, NodeCast};
 use dom::bindings::codegen::InheritTypes::{HTMLTextAreaElementDerived, HTMLFieldSetElementDerived};
 use dom::bindings::codegen::InheritTypes::{KeyboardEventCast, TextDerived};
-use dom::bindings::js::{JS, JSRef, Temporary};
+use dom::bindings::js::{JS, JSRef, Temporary, OptionalRootable};
 use dom::bindings::utils::{Reflectable, Reflector};
 use dom::document::{Document, DocumentHelpers};
-use dom::element::{AttributeHandlers, HTMLTextAreaElementTypeId};
+use dom::element::{AttributeHandlers, HTMLTextAreaElementTypeId, Element};
 use dom::event::Event;
 use dom::eventtarget::{EventTarget, NodeTargetTypeId};
 use dom::htmlelement::HTMLElement;
+use dom::htmlformelement::FormControl;
 use dom::keyboardevent::KeyboardEvent;
 use dom::node::{DisabledStateHelpers, Node, NodeHelpers, OtherNodeDamage, ElementNodeTypeId};
 use dom::node::{document_from_node};
@@ -124,6 +125,12 @@ impl<'a> HTMLTextAreaElementMethods for JSRef<'a, HTMLTextAreaElement> {
     // https://html.spec.whatwg.org/multipage/forms.html#dom-textarea-placeholder
     make_setter!(SetPlaceholder, "placeholder")
 
+    // https://html.spec.whatwg.org/multipage/forms.html#attr-textarea-readonly
+    make_bool_getter!(ReadOnly)
+
+    // https://html.spec.whatwg.org/multipage/forms.html#attr-textarea-readonly
+    make_bool_setter!(SetReadOnly, "readonly")
+
     // https://html.spec.whatwg.org/multipage/forms.html#dom-textarea-required
     make_bool_getter!(Required)
 
@@ -161,7 +168,7 @@ impl<'a> HTMLTextAreaElementMethods for JSRef<'a, HTMLTextAreaElement> {
         // if the element's dirty value flag is false, then the element's
         // raw value must be set to the value of the element's textContent IDL attribute
         if !self.value_changed.get() {
-            self.SetValue(node.GetTextContent().unwrap());
+            self.reset();
         }
     }
 
@@ -172,7 +179,9 @@ impl<'a> HTMLTextAreaElementMethods for JSRef<'a, HTMLTextAreaElement> {
 
     // https://html.spec.whatwg.org/multipage/forms.html#dom-textarea-value
     fn SetValue(self, value: DOMString) {
+        // TODO move the cursor to the end of the field
         self.textinput.borrow_mut().set_content(value);
+        self.value_changed.set(true);
         self.force_relayout();
     }
 }
@@ -286,8 +295,8 @@ impl<'a> VirtualMethods for JSRef<'a, HTMLTextAreaElement> {
             _ => (),
         }
 
-        if child.is_text() {
-            self.SetValue(self.DefaultValue());
+        if child.is_text() && !self.value_changed.get() {
+            self.reset();
         }
     }
 
@@ -326,3 +335,21 @@ impl Reflectable for HTMLTextAreaElement {
         self.htmlelement.reflector()
     }
 }
+
+impl<'a> FormControl<'a> for JSRef<'a, HTMLTextAreaElement> {
+    fn to_element(self) -> JSRef<'a, Element> {
+        ElementCast::from_ref(self)
+    }
+
+    // https://html.spec.whatwg.org/multipage/forms.html#concept-fe-mutable
+    fn mutable(self) -> bool {
+        // https://html.spec.whatwg.org/multipage/forms.html#the-textarea-element:concept-fe-mutable
+        !(self.Disabled() || self.ReadOnly())
+    }
+
+    fn reset(self) {
+        // https://html.spec.whatwg.org/multipage/forms.html#the-textarea-element:concept-form-reset-control
+        self.SetValue(self.DefaultValue());
+        self.value_changed.set(false);
+    }
+}
diff --git a/components/script/dom/webidls/HTMLFormElement.webidl b/components/script/dom/webidls/HTMLFormElement.webidl
index 1971680b5be..ce64cac7ec6 100644
--- a/components/script/dom/webidls/HTMLFormElement.webidl
+++ b/components/script/dom/webidls/HTMLFormElement.webidl
@@ -22,7 +22,7 @@ interface HTMLFormElement : HTMLElement {
   //getter (RadioNodeList or Element) (DOMString name);
 
   void submit();
-  //void reset();
+  void reset();
   //boolean checkValidity();
   //boolean reportValidity();
 
diff --git a/components/script/dom/webidls/HTMLInputElement.webidl b/components/script/dom/webidls/HTMLInputElement.webidl
index 434da309f21..47180432736 100644
--- a/components/script/dom/webidls/HTMLInputElement.webidl
+++ b/components/script/dom/webidls/HTMLInputElement.webidl
@@ -9,7 +9,7 @@ interface HTMLInputElement : HTMLElement {
   //         attribute DOMString alt;
   //         attribute DOMString autocomplete;
   //         attribute boolean autofocus;
-  //         attribute boolean defaultChecked;
+           attribute boolean defaultChecked;
            attribute boolean checked;
   //         attribute DOMString dirName;
            attribute boolean disabled;
@@ -38,7 +38,7 @@ interface HTMLInputElement : HTMLElement {
   //         attribute DOMString src;
   //         attribute DOMString step;
            attribute DOMString type;
-  //         attribute DOMString defaultValue;
+           attribute DOMString defaultValue;
   [TreatNullAs=EmptyString] attribute DOMString value;
   //         attribute Date? valueAsDate;
   //         attribute unrestricted double valueAsNumber;
diff --git a/components/script/dom/webidls/HTMLTextAreaElement.webidl b/components/script/dom/webidls/HTMLTextAreaElement.webidl
index 59d10658b14..4bc4510d2a2 100644
--- a/components/script/dom/webidls/HTMLTextAreaElement.webidl
+++ b/components/script/dom/webidls/HTMLTextAreaElement.webidl
@@ -16,7 +16,7 @@ interface HTMLTextAreaElement : HTMLElement {
   //         attribute long minLength;
            attribute DOMString name;
            attribute DOMString placeholder;
-  //         attribute boolean readOnly;
+           attribute boolean readOnly;
            attribute boolean required;
            attribute unsigned long rows;
            attribute DOMString wrap;
diff --git a/components/script/textinput.rs b/components/script/textinput.rs
index d39d22918c0..ed120aae943 100644
--- a/components/script/textinput.rs
+++ b/components/script/textinput.rs
@@ -295,6 +295,12 @@ impl TextInput {
             vec!(content)
         };
         self.edit_point.line = min(self.edit_point.line, self.lines.len() - 1);
-        self.edit_point.index = min(self.edit_point.index, self.current_line_length() - 1);
+
+        if self.current_line_length() == 0 {
+            self.edit_point.index = 0;
+        }
+        else {
+            self.edit_point.index = min(self.edit_point.index, self.current_line_length() - 1);
+        }
     }
 }