use return value of invoking event handlers to cancel the event

components/script/dom/eventtarget.rs

@@ -5,6 +5,7 @@
 use dom::bindings::callback::{CallbackContainer, ExceptionHandling, CallbackFunction};
 use dom::bindings::cell::DOMRefCell;
 use dom::bindings::codegen::Bindings::ErrorEventBinding::ErrorEventMethods;
+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::EventListenerBinding::EventListener;
@@ -188,13 +189,20 @@ impl CompiledEventListener {
                             let global = object.global();
                             let cx = global.r().get_cx();
                             let error = RootedValue::new(cx, event.Error(cx));
-                            let _ = handler.Call_(object,
+                            let return_value = handler.Call_(object,
-                                                  EventOrString::String(event.Message()),
+                                                             EventOrString::String(event.Message()),
-                                                  Some(event.Filename()),
+                                                             Some(event.Filename()),
-                                                  Some(event.Lineno()),
+                                                             Some(event.Lineno()),
-                                                  Some(event.Colno()),
+                                                             Some(event.Colno()),
-                                                  Some(error.handle()),
+                                                             Some(error.handle()),
-                                                  exception_handle);
+                                                             exception_handle);
+                            // Step 4
+                            if let Ok(return_value) = return_value {
+                                let return_value = RootedValue::new(cx, return_value);
+                                if return_value.handle().is_boolean() && return_value.handle().to_boolean() == true {
+                                    event.upcast::<Event>().PreventDefault();
+                                }
+                            }
                             return;
                         }
 
@@ -203,13 +211,26 @@ impl CompiledEventListener {
                     }
 
                     CommonEventHandler::EventHandler(ref handler) => {
-                        let _ = handler.Call_(object, event, exception_handle);
+                        if let Ok(value) = handler.Call_(object, event, exception_handle) {
+                            let global = object.global();
+                            let cx = global.r().get_cx();
+                            let value = RootedValue::new(cx, value);
+                            let value = value.handle();
+
+                            //Step 4
+                            let should_cancel = match event.type_() {
+                                atom!("mouseover") => value.is_boolean() && value.to_boolean() == true,
+                                atom!("beforeunload") => value.is_null(),
+                                _ => value.is_boolean() && value.to_boolean() == false
+                            };
+                            if should_cancel {
+                                event.PreventDefault();
+                            }
+                        }
                     }
                 }
-            },
+            }
         }
-
-        // TODO(#8490): step 4 (cancel event based on return value)
     }
 }
 
@@ -294,8 +315,8 @@ impl EventTarget {
     }
 
     pub fn dispatch_event_with_target(&self,
-                                  target: &EventTarget,
+                                      target: &EventTarget,
-                                  event: &Event) -> bool {
+                                      event: &Event) -> bool {
         dispatch_event(self, Some(target), event)
     }
 

components/script/dom/htmlelement.rs

@@ -180,6 +180,24 @@ impl HTMLElementMethods for HTMLElement {
         }
     }
 
+    // https://html.spec.whatwg.org/multipage/#handler-onblur
+    fn GetOnblur(&self) -> Option<Rc<EventHandlerNonNull>> {
+        if self.is_body_or_frameset() {
+            window_from_node(self).GetOnblur()
+        } else {
+            self.upcast::<EventTarget>().get_event_handler_common("blur")
+        }
+    }
+
+    // https://html.spec.whatwg.org/multipage/#handler-onblur
+    fn SetOnblur(&self, listener: Option<Rc<EventHandlerNonNull>>) {
+        if self.is_body_or_frameset() {
+            window_from_node(self).SetOnblur(listener)
+        } else {
+            self.upcast::<EventTarget>().set_event_handler_common("blur", listener)
+        }
+    }
+
     // https://html.spec.whatwg.org/multipage/#dom-click
     fn Click(&self) {
         if let Some(i) = self.downcast::<HTMLInputElement>() {

components/script/dom/macros.rs

@@ -332,19 +332,22 @@ macro_rules! error_event_handler(
 // As more methods get added, just update them here.
 macro_rules! global_event_handlers(
     () => (
+        event_handler!(blur, GetOnblur, SetOnblur);
         event_handler!(load, GetOnload, SetOnload);
         event_handler!(resize, GetOnresize, SetOnresize);
         global_event_handlers!(NoOnload);
 
     );
     (NoOnload) => (
+        event_handler!(change, GetOnchange, SetOnchange);
         event_handler!(click, GetOnclick, SetOnclick);
+        event_handler!(dblclick, GetOndblclick, SetOndblclick);
         error_event_handler!(error, GetOnerror, SetOnerror);
+        event_handler!(input, GetOninput, SetOninput);
         event_handler!(keydown, GetOnkeydown, SetOnkeydown);
         event_handler!(keypress, GetOnkeypress, SetOnkeypress);
         event_handler!(keyup, GetOnkeyup, SetOnkeyup);
-        event_handler!(input, GetOninput, SetOninput);
+        event_handler!(mouseover, GetOnmouseover, SetOnmouseover);
-        event_handler!(change, GetOnchange, SetOnchange);
         event_handler!(reset, GetOnreset, SetOnreset);
         event_handler!(submit, GetOnsubmit, SetOnsubmit);
         event_handler!(toggle, GetOntoggle, SetOntoggle);

components/script/dom/webidls/EventHandler.webidl

@@ -23,18 +23,22 @@ typedef OnErrorEventHandlerNonNull? OnErrorEventHandler;
 
 [NoInterfaceObject]
 interface GlobalEventHandlers {
+           attribute EventHandler onblur;
+           attribute EventHandler onchange;
            attribute EventHandler onclick;
+           attribute EventHandler ondblclick;
            attribute OnErrorEventHandler onerror;
-           attribute EventHandler onload;
            attribute EventHandler oninput;
            attribute EventHandler onkeydown;
            attribute EventHandler onkeypress;
            attribute EventHandler onkeyup;
-           attribute EventHandler onchange;
+           attribute EventHandler onload;
+           attribute EventHandler onmouseover;
            attribute EventHandler onreset;
+           attribute EventHandler onresize;
            attribute EventHandler onsubmit;
            attribute EventHandler ontoggle;
-           attribute EventHandler onresize;
+
 };
 
 [NoInterfaceObject]

tests/wpt/metadata/MANIFEST.json

@@ -34512,7 +34512,16 @@
   },
   "local_changes": {
     "deleted": [],
-    "items": {},
+    "items": {
+      "testharness": {
+        "html/webappapis/scripting/events/event-handler-processing-algorithm.html": [
+          {
+            "path": "html/webappapis/scripting/events/event-handler-processing-algorithm.html",
+            "url": "/html/webappapis/scripting/events/event-handler-processing-algorithm.html"
+          }
+        ]
+      }
+    },
     "reftest_nodes": {}
   },
   "reftest_nodes": {

tests/wpt/metadata/html/dom/interfaces.html.ini

@@ -75,9 +75,6 @@
   [Document interface: attribute onautocompleteerror]
     expected: FAIL
 
-  [Document interface: attribute onblur]
-    expected: FAIL
-
   [Document interface: attribute oncancel]
     expected: FAIL
 
@@ -96,9 +93,6 @@
   [Document interface: attribute oncuechange]
     expected: FAIL
 
-  [Document interface: attribute ondblclick]
-    expected: FAIL
-
   [Document interface: attribute ondrag]
     expected: FAIL
 
@@ -162,9 +156,6 @@
   [Document interface: attribute onmouseout]
     expected: FAIL
 
-  [Document interface: attribute onmouseover]
-    expected: FAIL
-
   [Document interface: attribute onmouseup]
     expected: FAIL
 
@@ -1611,9 +1602,6 @@
   [HTMLElement interface: attribute onautocompleteerror]
     expected: FAIL
 
-  [HTMLElement interface: attribute onblur]
-    expected: FAIL
-
   [HTMLElement interface: attribute oncancel]
     expected: FAIL
 
@@ -1632,9 +1620,6 @@
   [HTMLElement interface: attribute oncuechange]
     expected: FAIL
 
-  [HTMLElement interface: attribute ondblclick]
-    expected: FAIL
-
   [HTMLElement interface: attribute ondrag]
     expected: FAIL
 
@@ -1698,9 +1683,6 @@
   [HTMLElement interface: attribute onmouseout]
     expected: FAIL
 
-  [HTMLElement interface: attribute onmouseover]
-    expected: FAIL
-
   [HTMLElement interface: attribute onmouseup]
     expected: FAIL
 
@@ -1839,9 +1821,6 @@
   [HTMLElement interface: document.createElement("noscript") must inherit property "onautocompleteerror" with the proper type (34)]
     expected: FAIL
 
-  [HTMLElement interface: document.createElement("noscript") must inherit property "onblur" with the proper type (35)]
-    expected: FAIL
-
   [HTMLElement interface: document.createElement("noscript") must inherit property "oncancel" with the proper type (36)]
     expected: FAIL
 
@@ -1860,9 +1839,6 @@
   [HTMLElement interface: document.createElement("noscript") must inherit property "oncuechange" with the proper type (43)]
     expected: FAIL
 
-  [HTMLElement interface: document.createElement("noscript") must inherit property "ondblclick" with the proper type (44)]
-    expected: FAIL
-
   [HTMLElement interface: document.createElement("noscript") must inherit property "ondrag" with the proper type (45)]
     expected: FAIL
 
@@ -1926,9 +1902,6 @@
   [HTMLElement interface: document.createElement("noscript") must inherit property "onmouseout" with the proper type (71)]
     expected: FAIL
 
-  [HTMLElement interface: document.createElement("noscript") must inherit property "onmouseover" with the proper type (72)]
-    expected: FAIL
-
   [HTMLElement interface: document.createElement("noscript") must inherit property "onmouseup" with the proper type (73)]
     expected: FAIL
 
@@ -8610,9 +8583,6 @@
   [Document interface: document.implementation.createDocument(null, "", null) must inherit property "onautocompleteerror" with the proper type (96)]
     expected: FAIL
 
-  [Document interface: document.implementation.createDocument(null, "", null) must inherit property "onblur" with the proper type (97)]
-    expected: FAIL
-
   [Document interface: document.implementation.createDocument(null, "", null) must inherit property "oncancel" with the proper type (98)]
     expected: FAIL
 
@@ -8631,9 +8601,6 @@
   [Document interface: document.implementation.createDocument(null, "", null) must inherit property "oncuechange" with the proper type (105)]
     expected: FAIL
 
-  [Document interface: document.implementation.createDocument(null, "", null) must inherit property "ondblclick" with the proper type (106)]
-    expected: FAIL
-
   [Document interface: document.implementation.createDocument(null, "", null) must inherit property "ondrag" with the proper type (107)]
     expected: FAIL
 
@@ -8697,9 +8664,6 @@
   [Document interface: document.implementation.createDocument(null, "", null) must inherit property "onmouseout" with the proper type (133)]
     expected: FAIL
 
-  [Document interface: document.implementation.createDocument(null, "", null) must inherit property "onmouseover" with the proper type (134)]
-    expected: FAIL
-
   [Document interface: document.implementation.createDocument(null, "", null) must inherit property "onmouseup" with the proper type (135)]
     expected: FAIL
 

tests/wpt/metadata/html/webappapis/scripting/events/event-handler-attributes-body-window.html.ini

@@ -1,8 +1,5 @@
 [event-handler-attributes-body-window.html]
   type: testharness
-  [blur]
-    expected: FAIL
-
   [error]
     expected: FAIL
 

tests/wpt/metadata/html/webappapis/scripting/events/event-handler-processing-algorithm.html.ini

@@ -0,0 +1,4 @@
+[event-handler-processing-algorithm.html]
+  type: testharness
+  [beforeunload listener returning null cancels event]
+    expected: FAIL

tests/wpt/web-platform-tests/html/webappapis/scripting/events/event-handler-processing-algorithm.html

@@ -0,0 +1,63 @@
+<!DOCTYPE html>
+<title>Event handlers processing algorithm</title>
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script
+ <body>
+ <div id="foo" style="width: 100px; height: 100px; background-color: black"></div>
+ <script>
+ async_test(function(t) {
+     var ev = new Event('mouseover', {cancelable: true});
+     document.getElementById("foo").onmouseover = t.step_func(function() { return true });
+     document.getElementById("foo").dispatchEvent(ev);
+     assert_equals(ev.defaultPrevented, true)
+     t.done();
+ }, "mouseover listener returning true cancels event");
+
+ async_test(function(t) {
+     var ev = new Event('mouseover', {cancelable: true});
+     document.getElementById("foo").onmouseover = t.step_func(function() { return false; });
+     document.getElementById("foo").dispatchEvent(ev);
+     assert_equals(ev.defaultPrevented, false);
+     t.done();
+ }, "mouseover listener returning false doesn't cancel event");
+
+ async_test(function(t) {
+     var ev = new Event('beforeunload', {cancelable: true});
+     window.onbeforeunload = t.step_func(function() {return null});
+     window.dispatchEvent(ev);
+     assert_equals(ev.defaultPrevented, true);
+     t.done();
+ }, "beforeunload listener returning null cancels event");
+
+ async_test(function(t) {
+     var ev = new Event('beforeunload', {cancelable: true});
+     window.onbeforeunload = t.step_func(function() {return true});
+     window.dispatchEvent(ev);
+     assert_equals(ev.defaultPrevented, false);
+     t.done();
+ }, "beforeunload listener returning non-null doesn't cancel event");
+
+ async_test(function(t) {
+     var ev = new Event("click", {cancelable: true});
+     document.getElementById("foo").onclick = t.step_func(function() { return false; });
+     document.getElementById("foo").dispatchEvent(ev);
+     assert_equals(ev.defaultPrevented, true);
+     t.done();
+ }, "click listener returning false cancels event");
+
+ async_test(function(t) {
+     var ev = new Event("blur", {cancelable: true});
+     document.getElementById("foo").onblur = t.step_func(function() { return false; });
+     document.getElementById("foo").dispatchEvent(ev);
+     assert_equals(ev.defaultPrevented, true);
+     t.done();
+ }, "blur listener returning false cancels event");
+
+ async_test(function(t) {
+     var ev = new Event("dblclick", {cancelable: true});
+     document.getElementById("foo").ondblclick = t.step_func(function() { return false; });
+     document.getElementById("foo").dispatchEvent(ev);
+     assert_equals(ev.defaultPrevented, true);
+     t.done();
+ }, "dblclick listener returning false cancels event");
+</script>