Auto merge of #13397 - aochagavia:dispatch-event, r=Ms2ger

Return an enum instead of a boolean from dispatch_event

Fixes #13196

---
- [X] `./mach build -d` does not report any errors
- [X] `./mach test-tidy` does not report any errors
- [X] These changes fix #13196.
- [X] These changes do not require tests because the functionality hasn't changed

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---
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7 files changed, 45 insertions, 17 deletions

diff --git a/components/script/dom/dedicatedworkerglobalscope.rs b/components/script/dom/dedicatedworkerglobalscope.rs
index 589489debce..c425c38b86b 100644
--- a/components/script/dom/dedicatedworkerglobalscope.rs
+++ b/components/script/dom/dedicatedworkerglobalscope.rs
@@ -19,6 +19,7 @@ use dom::bindings::str::DOMString;
 use dom::bindings::structuredclone::StructuredCloneData;
 use dom::errorevent::ErrorEvent;
 use dom::event::{Event, EventBubbles, EventCancelable};
+use dom::eventdispatcher::EventStatus;
 use dom::eventtarget::EventTarget;
 use dom::messageevent::MessageEvent;
 use dom::worker::{TrustedWorkerAddress, WorkerErrorHandler, WorkerMessageHandler};
@@ -370,8 +371,10 @@ impl DedicatedWorkerGlobalScope {
                                     value);
 
         // Step 13.
-        let handled = !event.upcast::<Event>().fire(self.upcast::<EventTarget>());
-        if !handled {
+        let event_status = event.upcast::<Event>().fire(self.upcast::<EventTarget>());
+
+        // Step 15
+        if event_status == EventStatus::NotCanceled {
             let worker = self.worker.borrow().as_ref().unwrap().clone();
             // TODO: Should use the DOM manipulation task source.
             self.parent_sender
@@ -380,6 +383,7 @@ impl DedicatedWorkerGlobalScope {
                 .unwrap();
         }
 
+        // Step 14
         self.in_error_reporting_mode.set(false);
     }
 }
diff --git a/components/script/dom/document.rs b/components/script/dom/document.rs
index 2cca84a625a..1b91e743a78 100644
--- a/components/script/dom/document.rs
+++ b/components/script/dom/document.rs
@@ -41,6 +41,7 @@ use dom::domimplementation::DOMImplementation;
 use dom::element::{Element, ElementCreator};
 use dom::errorevent::ErrorEvent;
 use dom::event::{Event, EventBubbles, EventCancelable};
+use dom::eventdispatcher::EventStatus;
 use dom::eventtarget::EventTarget;
 use dom::focusevent::FocusEvent;
 use dom::forcetouchevent::ForceTouchEvent;
@@ -1119,7 +1120,11 @@ impl Document {
         window.reflow(ReflowGoal::ForDisplay,
                       ReflowQueryType::NoQuery,
                       ReflowReason::MouseEvent);
-        result
+
+        match result {
+            EventStatus::Canceled => false,
+            EventStatus::NotCanceled => true
+        }
     }
 
     /// The entry point for all key processing for web content
diff --git a/components/script/dom/event.rs b/components/script/dom/event.rs
index 07330a776ae..a6dfe7c9ac4 100644
--- a/components/script/dom/event.rs
+++ b/components/script/dom/event.rs
@@ -11,6 +11,7 @@ use dom::bindings::js::{JS, MutNullableHeap, Root};
 use dom::bindings::refcounted::Trusted;
 use dom::bindings::reflector::{Reflector, reflect_dom_object};
 use dom::bindings::str::DOMString;
+use dom::eventdispatcher::EventStatus;
 use dom::eventtarget::EventTarget;
 use script_thread::Runnable;
 use std::cell::Cell;
@@ -153,6 +154,13 @@ impl Event {
         self.cancelable.set(cancelable);
     }
 
+    pub fn status(&self) -> EventStatus {
+        match self.DefaultPrevented() {
+            true => EventStatus::Canceled,
+            false => EventStatus::NotCanceled
+        }
+    }
+
     #[inline]
     pub fn set_current_target(&self, val: &EventTarget) {
         self.current_target.set(Some(val));
@@ -303,7 +311,7 @@ impl Event {
     }
 
     // https://html.spec.whatwg.org/multipage/#fire-a-simple-event
-    pub fn fire(&self, target: &EventTarget) -> bool {
+    pub fn fire(&self, target: &EventTarget) -> EventStatus {
         self.set_trusted(true);
         target.dispatch_event(self)
     }
diff --git a/components/script/dom/eventdispatcher.rs b/components/script/dom/eventdispatcher.rs
index e9525f17604..28ea0b42b31 100644
--- a/components/script/dom/eventdispatcher.rs
+++ b/components/script/dom/eventdispatcher.rs
@@ -103,10 +103,16 @@ fn dispatch_to_listeners(event: &Event, target: &EventTarget, event_path: &[&Eve
     }
 }
 
+#[derive(PartialEq)]
+pub enum EventStatus {
+    Canceled,
+    NotCanceled
+}
+
 // https://dom.spec.whatwg.org/#concept-event-dispatch
 pub fn dispatch_event(target: &EventTarget,
                       target_override: Option<&EventTarget>,
-                      event: &Event) -> bool {
+                      event: &Event) -> EventStatus {
     assert!(!event.dispatching());
     assert!(event.initialized());
     assert_eq!(event.phase(), EventPhase::None);
@@ -126,7 +132,7 @@ pub fn dispatch_event(target: &EventTarget,
         event.clear_dispatching_flags();
 
         // Step 14.
-        return !event.DefaultPrevented();
+        return event.status();
     }
 
     // Step 3. The "invoke" algorithm is only used on `target` separately,
@@ -165,8 +171,8 @@ pub fn dispatch_event(target: &EventTarget,
     // Step 10-12.
     event.clear_dispatching_flags();
 
-    // Step 13.
-    !event.DefaultPrevented()
+    // Step 14.
+    event.status()
 }
 
 // https://dom.spec.whatwg.org/#concept-event-listener-invoke
diff --git a/components/script/dom/eventtarget.rs b/components/script/dom/eventtarget.rs
index c941eb8e20e..1d3efd59b19 100644
--- a/components/script/dom/eventtarget.rs
+++ b/components/script/dom/eventtarget.rs
@@ -23,7 +23,7 @@ use dom::bindings::str::DOMString;
 use dom::element::Element;
 use dom::errorevent::ErrorEvent;
 use dom::event::{Event, EventBubbles, EventCancelable};
-use dom::eventdispatcher::dispatch_event;
+use dom::eventdispatcher::{EventStatus, dispatch_event};
 use dom::node::document_from_node;
 use dom::virtualmethods::VirtualMethods;
 use dom::window::Window;
@@ -300,11 +300,11 @@ impl EventTarget {
 
     pub fn dispatch_event_with_target(&self,
                                       target: &EventTarget,
-                                      event: &Event) -> bool {
+                                      event: &Event) -> EventStatus {
         dispatch_event(self, Some(target), event)
     }
 
-    pub fn dispatch_event(&self, event: &Event) -> bool {
+    pub fn dispatch_event(&self, event: &Event) -> EventStatus {
         dispatch_event(self, None, event)
     }
 
@@ -560,7 +560,10 @@ impl EventTargetMethods for EventTarget {
             return Err(Error::InvalidState);
         }
         event.set_trusted(false);
-        Ok(self.dispatch_event(event))
+        Ok(match self.dispatch_event(event) {
+            EventStatus::Canceled => false,
+            EventStatus::NotCanceled => true
+        })
     }
 }
 
diff --git a/components/script/dom/htmlscriptelement.rs b/components/script/dom/htmlscriptelement.rs
index 566b69967d4..4b16908968f 100644
--- a/components/script/dom/htmlscriptelement.rs
+++ b/components/script/dom/htmlscriptelement.rs
@@ -20,6 +20,7 @@ use dom::bindings::str::DOMString;
 use dom::document::Document;
 use dom::element::{AttributeMutation, Element, ElementCreator};
 use dom::event::{Event, EventBubbles, EventCancelable};
+use dom::eventdispatcher::EventStatus;
 use dom::htmlelement::HTMLElement;
 use dom::node::{ChildrenMutation, CloneChildrenFlag, Node};
 use dom::node::{document_from_node, window_from_node};
@@ -488,7 +489,7 @@ impl HTMLScriptElement {
         }
 
         // TODO(#12446): beforescriptexecute.
-        if !self.dispatch_before_script_execute_event() {
+        if self.dispatch_before_script_execute_event() == EventStatus::Canceled {
             return;
         }
 
@@ -535,7 +536,7 @@ impl HTMLScriptElement {
         window.dom_manipulation_task_source().queue_simple_event(self.upcast(), atom!("error"), window.r());
     }
 
-    pub fn dispatch_before_script_execute_event(&self) -> bool {
+    pub fn dispatch_before_script_execute_event(&self) -> EventStatus {
         self.dispatch_event(atom!("beforescriptexecute"),
                             EventBubbles::Bubbles,
                             EventCancelable::Cancelable)
@@ -606,7 +607,7 @@ impl HTMLScriptElement {
     fn dispatch_event(&self,
                       type_: Atom,
                       bubbles: EventBubbles,
-                      cancelable: EventCancelable) -> bool {
+                      cancelable: EventCancelable) -> EventStatus {
         let window = window_from_node(self);
         let window = window.r();
         let event = Event::new(GlobalRef::Window(window), type_, bubbles, cancelable);
diff --git a/components/script/dom/worker.rs b/components/script/dom/worker.rs
index 1df110a12e5..1821b2d2dee 100644
--- a/components/script/dom/worker.rs
+++ b/components/script/dom/worker.rs
@@ -19,6 +19,7 @@ use dom::bindings::structuredclone::StructuredCloneData;
 use dom::dedicatedworkerglobalscope::DedicatedWorkerGlobalScope;
 use dom::errorevent::ErrorEvent;
 use dom::event::{Event, EventBubbles, EventCancelable};
+use dom::eventdispatcher::EventStatus;
 use dom::eventtarget::EventTarget;
 use dom::messageevent::MessageEvent;
 use dom::workerglobalscope::prepare_workerscope_init;
@@ -153,8 +154,8 @@ impl Worker {
                                     error_info.column,
                                     unsafe { NullHandleValue });
 
-        let handled = !event.upcast::<Event>().fire(self.upcast::<EventTarget>());
-        if handled {
+        let event_status = event.upcast::<Event>().fire(self.upcast::<EventTarget>());
+        if event_status == EventStatus::Canceled {
             return;
         }