Auto merge of #14738 - Wafflespeanut:keypress, r=jdm

Properly dispatch keypress event

<!-- Please describe your changes on the following line: -->

This was an attempt to fix #14659. It turned out that the problem wasn't what I thought it was. So, I didn't fix that. On the brighter side, this fixes two related issues.

- Previously, we were unable to launch `keypress` events from `input` and `textarea` elements, because [we'd been cancelling](https://github.com/servo/servo/blob/1327ebd52f53f5f6637a12fab6cf0cad0aa0be6f/components/script/dom/htmlinputelement.rs#L1120-L1124) the key events, so that they don't trigger window navigation - #8400). I've introduced an enum to represent an additional state to an event's cancellation.
- [According to the spec](https://w3c.github.io/uievents/#keypress-event-order), `keypress` (if available) should be dispatched immediately after `keydown`, and it should be followed by `input`. Canceling `keypress` should also cancel `input`. But, we'd been dispatching `input` before `keypress`. We now dispatch `input` once the `keypress` event is on the respective elements.

---
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- [x] `./mach build -d` does not report any errors
- [x] `./mach test-tidy` does not report any errors

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- [x] These changes do not require tests because it's a refactor?

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r? @jdm or anyone interested

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5 files changed, 93 insertions, 62 deletions

diff --git a/components/atoms/static_atoms.txt b/components/atoms/static_atoms.txt
index e59c9cad809..c2a4ea84ec2 100644
--- a/components/atoms/static_atoms.txt
+++ b/components/atoms/static_atoms.txt
@@ -52,6 +52,7 @@ beforeunload
 message
 click
 keydown
+keypress
 abort
 beforescriptexecute
 afterscriptexecute
diff --git a/components/script/dom/document.rs b/components/script/dom/document.rs
index 79acb69096d..83dc980716c 100644
--- a/components/script/dom/document.rs
+++ b/components/script/dom/document.rs
@@ -13,7 +13,6 @@ use dom::bindings::codegen::Bindings::DOMRectBinding::DOMRectMethods;
 use dom::bindings::codegen::Bindings::DocumentBinding;
 use dom::bindings::codegen::Bindings::DocumentBinding::{DocumentMethods, DocumentReadyState};
 use dom::bindings::codegen::Bindings::ElementBinding::ElementMethods;
-use dom::bindings::codegen::Bindings::EventBinding::EventMethods;
 use dom::bindings::codegen::Bindings::EventHandlerBinding::EventHandlerNonNull;
 use dom::bindings::codegen::Bindings::EventHandlerBinding::OnErrorEventHandlerNonNull;
 use dom::bindings::codegen::Bindings::NodeBinding::NodeMethods;
@@ -41,7 +40,7 @@ use dom::documenttype::DocumentType;
 use dom::domimplementation::DOMImplementation;
 use dom::element::{Element, ElementCreator, ElementPerformFullscreenEnter, ElementPerformFullscreenExit};
 use dom::errorevent::ErrorEvent;
-use dom::event::{Event, EventBubbles, EventCancelable};
+use dom::event::{Event, EventBubbles, EventCancelable, EventDefault};
 use dom::eventdispatcher::EventStatus;
 use dom::eventtarget::EventTarget;
 use dom::focusevent::FocusEvent;
@@ -1308,10 +1307,10 @@ impl Document {
                                           props.key_code);
         let event = keyevent.upcast::<Event>();
         event.fire(target);
-        let mut prevented = event.DefaultPrevented();
+        let mut cancel_state = event.get_cancel_state();
 
         // https://w3c.github.io/uievents/#keys-cancelable-keys
-        if state != KeyState::Released && props.is_printable() && !prevented {
+        if state != KeyState::Released && props.is_printable() && cancel_state != EventDefault::Prevented {
             // https://w3c.github.io/uievents/#keypress-event-order
             let event = KeyboardEvent::new(&self.window,
                                            DOMString::from("keypress"),
@@ -1334,40 +1333,39 @@ impl Document {
                                            0);
             let ev = event.upcast::<Event>();
             ev.fire(target);
-            prevented = ev.DefaultPrevented();
-            // TODO: if keypress event is canceled, prevent firing input events
+            cancel_state = ev.get_cancel_state();
         }
 
-        if !prevented {
+        if cancel_state == EventDefault::Allowed {
             constellation.send(ConstellationMsg::SendKeyEvent(ch, key, state, modifiers)).unwrap();
-        }
 
-        // This behavior is unspecced
-        // We are supposed to dispatch synthetic click activation for Space and/or Return,
-        // however *when* we do it is up to us
-        // I'm dispatching it after the key event so the script has a chance to cancel it
-        // https://www.w3.org/Bugs/Public/show_bug.cgi?id=27337
-        match key {
-            Key::Space if !prevented && state == KeyState::Released => {
-                let maybe_elem = target.downcast::<Element>();
-                if let Some(el) = maybe_elem {
-                    synthetic_click_activation(el,
-                                               false,
-                                               false,
-                                               false,
-                                               false,
-                                               ActivationSource::NotFromClick)
+            // This behavior is unspecced
+            // We are supposed to dispatch synthetic click activation for Space and/or Return,
+            // however *when* we do it is up to us.
+            // Here, we're dispatching it after the key event so the script has a chance to cancel it
+            // https://www.w3.org/Bugs/Public/show_bug.cgi?id=27337
+            match key {
+                Key::Space if state == KeyState::Released => {
+                    let maybe_elem = target.downcast::<Element>();
+                    if let Some(el) = maybe_elem {
+                        synthetic_click_activation(el,
+                                                   false,
+                                                   false,
+                                                   false,
+                                                   false,
+                                                   ActivationSource::NotFromClick)
+                    }
                 }
-            }
-            Key::Enter if !prevented && state == KeyState::Released => {
-                let maybe_elem = target.downcast::<Element>();
-                if let Some(el) = maybe_elem {
-                    if let Some(a) = el.as_maybe_activatable() {
-                        a.implicit_submission(ctrl, alt, shift, meta);
+                Key::Enter if state == KeyState::Released => {
+                    let maybe_elem = target.downcast::<Element>();
+                    if let Some(el) = maybe_elem {
+                        if let Some(a) = el.as_maybe_activatable() {
+                            a.implicit_submission(ctrl, alt, shift, meta);
+                        }
                     }
                 }
+                _ => (),
             }
-            _ => (),
         }
 
         self.window.reflow(ReflowGoal::ForDisplay,
diff --git a/components/script/dom/event.rs b/components/script/dom/event.rs
index d471c25d873..fa3b9bfae6b 100644
--- a/components/script/dom/event.rs
+++ b/components/script/dom/event.rs
@@ -77,6 +77,28 @@ impl From<bool> for EventCancelable {
     }
 }
 
+/// An enum to indicate whether the default action of an event is allowed.
+///
+/// This should've been a bool. Instead, it's an enum, because, aside from the allowed/canceled
+/// states, we also need something to stop the event from being handled again (without cancelling
+/// the event entirely). For example, an Up/Down `KeyEvent` inside a `textarea` element will
+/// trigger the cursor to go up/down if the text inside the element spans multiple lines. This enum
+/// helps us to prevent such events from being [sent to the constellation][msg] where it will be
+/// handled once again for page scrolling (which is definitely not what we'd want).
+///
+/// [msg]: https://doc.servo.org/script_traits/enum.ConstellationMsg.html#variant.KeyEvent
+///
+#[derive(JSTraceable, HeapSizeOf, Copy, Clone, PartialEq)]
+pub enum EventDefault {
+    /// The default action of the event is allowed (constructor's default)
+    Allowed,
+    /// The default action has been prevented by calling `PreventDefault`
+    Prevented,
+    /// The event has been handled somewhere in the DOM, and it should be prevented from being
+    /// re-handled elsewhere. This doesn't affect the judgement of `DefaultPrevented`
+    Handled,
+}
+
 #[dom_struct]
 pub struct Event {
     reflector_: Reflector,
@@ -84,7 +106,7 @@ pub struct Event {
     target: MutNullableJS<EventTarget>,
     type_: DOMRefCell<Atom>,
     phase: Cell<EventPhase>,
-    canceled: Cell<bool>,
+    canceled: Cell<EventDefault>,
     stop_propagation: Cell<bool>,
     stop_immediate: Cell<bool>,
     cancelable: Cell<bool>,
@@ -103,7 +125,7 @@ impl Event {
             target: Default::default(),
             type_: DOMRefCell::new(atom!("")),
             phase: Cell::new(EventPhase::None),
-            canceled: Cell::new(false),
+            canceled: Cell::new(EventDefault::Allowed),
             stop_propagation: Cell::new(false),
             stop_immediate: Cell::new(false),
             cancelable: Cell::new(false),
@@ -146,7 +168,7 @@ impl Event {
         self.initialized.set(true);
         self.stop_propagation.set(false);
         self.stop_immediate.set(false);
-        self.canceled.set(false);
+        self.canceled.set(EventDefault::Allowed);
         self.trusted.set(false);
         self.target.set(None);
         *self.type_.borrow_mut() = type_;
@@ -229,6 +251,16 @@ impl Event {
     pub fn type_(&self) -> Atom {
         self.type_.borrow().clone()
     }
+
+    #[inline]
+    pub fn mark_as_handled(&self) {
+        self.canceled.set(EventDefault::Handled);
+    }
+
+    #[inline]
+    pub fn get_cancel_state(&self) -> EventDefault {
+        self.canceled.get()
+    }
 }
 
 impl EventMethods for Event {
@@ -254,13 +286,13 @@ impl EventMethods for Event {
 
     // https://dom.spec.whatwg.org/#dom-event-defaultprevented
     fn DefaultPrevented(&self) -> bool {
-        self.canceled.get()
+        self.canceled.get() == EventDefault::Prevented
     }
 
     // https://dom.spec.whatwg.org/#dom-event-preventdefault
     fn PreventDefault(&self) {
         if self.cancelable.get() {
-            self.canceled.set(true)
+            self.canceled.set(EventDefault::Prevented)
         }
     }
 
diff --git a/components/script/dom/htmlinputelement.rs b/components/script/dom/htmlinputelement.rs
index eb344ef0a79..d133efd5e14 100755
--- a/components/script/dom/htmlinputelement.rs
+++ b/components/script/dom/htmlinputelement.rs
@@ -1105,28 +1105,29 @@ impl VirtualMethods for HTMLInputElement {
                         DispatchInput => {
                             self.value_changed.set(true);
                             self.update_placeholder_shown_state();
-
-                            if event.IsTrusted() {
-                                let window = window_from_node(self);
-                                let _ = window.user_interaction_task_source().queue_event(
-                                    &self.upcast(),
-                                    atom!("input"),
-                                    EventBubbles::Bubbles,
-                                    EventCancelable::NotCancelable,
-                                    &window);
-                            }
-
                             self.upcast::<Node>().dirty(NodeDamage::OtherNodeDamage);
-                            event.PreventDefault();
+                            event.mark_as_handled();
                         }
                         RedrawSelection => {
                             self.upcast::<Node>().dirty(NodeDamage::OtherNodeDamage);
-                            event.PreventDefault();
+                            event.mark_as_handled();
                         }
                         Nothing => (),
                     }
                 }
-        }
+        } else if event.type_() == atom!("keypress") && !event.DefaultPrevented() &&
+            (self.input_type.get() == InputType::InputText ||
+             self.input_type.get() == InputType::InputPassword) {
+                if event.IsTrusted() {
+                    let window = window_from_node(self);
+                    let _ = window.user_interaction_task_source()
+                                  .queue_event(&self.upcast(),
+                                               atom!("input"),
+                                               EventBubbles::Bubbles,
+                                               EventCancelable::NotCancelable,
+                                               &window);
+                }
+            }
     }
 }
 
diff --git a/components/script/dom/htmltextareaelement.rs b/components/script/dom/htmltextareaelement.rs
index fd5b42fa25c..2582b13514a 100755
--- a/components/script/dom/htmltextareaelement.rs
+++ b/components/script/dom/htmltextareaelement.rs
@@ -403,27 +403,26 @@ impl VirtualMethods for HTMLTextAreaElement {
                     KeyReaction::DispatchInput => {
                         self.value_changed.set(true);
                         self.update_placeholder_shown_state();
-
-                        if event.IsTrusted() {
-                            let window = window_from_node(self);
-                            let _ = window.user_interaction_task_source().queue_event(
-                                &self.upcast(),
-                                atom!("input"),
-                                EventBubbles::Bubbles,
-                                EventCancelable::NotCancelable,
-                                &window);
-                        }
-
                         self.upcast::<Node>().dirty(NodeDamage::OtherNodeDamage);
-                        event.PreventDefault();
+                        event.mark_as_handled();
                     }
                     KeyReaction::RedrawSelection => {
                         self.upcast::<Node>().dirty(NodeDamage::OtherNodeDamage);
-                        event.PreventDefault();
+                        event.mark_as_handled();
                     }
                     KeyReaction::Nothing => (),
                 }
             }
+        } else if event.type_() == atom!("keypress") && !event.DefaultPrevented() {
+            if event.IsTrusted() {
+                let window = window_from_node(self);
+                let _ = window.user_interaction_task_source()
+                              .queue_event(&self.upcast(),
+                                           atom!("input"),
+                                           EventBubbles::Bubbles,
+                                           EventCancelable::NotCancelable,
+                                           &window);
+            }
         }
     }
 }