webgl: Implement WebGLContextEvent and use it on context creation error

spec: https://www.khronos.org/registry/webgl/specs/latest/1.0/#5.15

components/script/dom/event.rs

@@ -36,7 +36,8 @@ pub enum EventTypeId {
     StorageEvent,
     UIEvent(UIEventTypeId),
     ErrorEvent,
-    CloseEvent
+    CloseEvent,
+    WebGLContextEvent,
 }
 
 #[derive(PartialEq, HeapSizeOf)]

components/script/dom/mod.rs

@@ -335,6 +335,7 @@ pub mod validitystate;
 pub mod virtualmethods;
 pub mod webglactiveinfo;
 pub mod webglbuffer;
+pub mod webglcontextevent;
 pub mod webglframebuffer;
 pub mod webglobject;
 pub mod webglprogram;

components/script/dom/webglcontextevent.rs

@@ -0,0 +1,87 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * 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::EventBinding::EventMethods;
+use dom::bindings::codegen::Bindings::WebGLContextEventBinding;
+use dom::bindings::codegen::Bindings::WebGLContextEventBinding::WebGLContextEventInit;
+use dom::bindings::codegen::Bindings::WebGLContextEventBinding::WebGLContextEventMethods;
+use dom::bindings::codegen::InheritTypes::{WebGLContextEventDerived, EventCast};
+use dom::bindings::error::Fallible;
+use dom::bindings::global::GlobalRef;
+use dom::bindings::js::{Root, RootedReference};
+use dom::bindings::utils::reflect_dom_object;
+use dom::event::{Event, EventBubbles, EventCancelable, EventTypeId};
+use util::str::DOMString;
+
+#[dom_struct]
+pub struct WebGLContextEvent {
+    event: Event,
+    status_message: DOMString,
+}
+
+impl WebGLContextEventMethods for WebGLContextEvent {
+    // https://www.khronos.org/registry/webgl/specs/latest/1.0/#5.15
+    fn StatusMessage(&self) -> DOMString {
+        self.status_message.clone()
+    }
+}
+
+impl WebGLContextEventDerived for Event {
+    fn is_webglcontextevent(&self) -> bool {
+        *self.type_id() == EventTypeId::WebGLContextEvent
+    }
+}
+
+impl WebGLContextEvent {
+    pub fn new_inherited(type_id: EventTypeId, status_message: DOMString) -> WebGLContextEvent {
+        WebGLContextEvent {
+            event: Event::new_inherited(type_id),
+            status_message: status_message,
+        }
+    }
+
+    pub fn new(global: GlobalRef,
+               type_: DOMString,
+               bubbles: EventBubbles,
+               cancelable: EventCancelable,
+               status_message: DOMString) -> Root<WebGLContextEvent> {
+        let event = reflect_dom_object(
+                        box WebGLContextEvent::new_inherited(EventTypeId::WebGLContextEvent, status_message),
+                        global,
+                        WebGLContextEventBinding::Wrap);
+
+        {
+            let parent = EventCast::from_ref(event.r());
+            parent.InitEvent(type_, bubbles == EventBubbles::Bubbles, cancelable == EventCancelable::Cancelable);
+        }
+
+        event
+    }
+
+    pub fn Constructor(global: GlobalRef,
+                       type_: DOMString,
+                       init: &WebGLContextEventInit) -> Fallible<Root<WebGLContextEvent>> {
+        let status_message = match init.statusMessage.as_ref() {
+            Some(message) => message.clone(),
+            None => "".to_owned(),
+        };
+
+        let bubbles = if init.parent.bubbles {
+            EventBubbles::Bubbles
+        } else {
+            EventBubbles::DoesNotBubble
+        };
+
+        let cancelable = if init.parent.cancelable {
+            EventCancelable::Cancelable
+        } else {
+            EventCancelable::NotCancelable
+        };
+
+        Ok(WebGLContextEvent::new(global, type_,
+                                  bubbles,
+                                  cancelable,
+                                  status_message))
+    }
+}

components/script/dom/webglrenderingcontext.rs

@@ -8,16 +8,18 @@ use canvas_traits::{WebGLFramebufferBindingRequest, WebGLShaderParameter};
 use dom::bindings::codegen::Bindings::WebGLRenderingContextBinding::WebGLRenderingContextConstants as constants;
 use dom::bindings::codegen::Bindings::WebGLRenderingContextBinding::{WebGLRenderingContextMethods};
 use dom::bindings::codegen::Bindings::WebGLRenderingContextBinding::{self, WebGLContextAttributes};
-use dom::bindings::codegen::InheritTypes::NodeCast;
+use dom::bindings::codegen::InheritTypes::{EventCast, EventTargetCast, NodeCast};
 use dom::bindings::codegen::UnionTypes::ImageDataOrHTMLImageElementOrHTMLCanvasElementOrHTMLVideoElement;
 use dom::bindings::conversions::ToJSValConvertible;
 use dom::bindings::global::{GlobalField, GlobalRef};
 use dom::bindings::js::{JS, LayoutJS, Root};
 use dom::bindings::utils::{Reflector, reflect_dom_object};
+use dom::event::{EventBubbles, EventCancelable};
 use dom::htmlcanvaselement::HTMLCanvasElement;
 use dom::htmlcanvaselement::utils as canvas_utils;
 use dom::node::{NodeDamage, window_from_node};
 use dom::webglbuffer::WebGLBuffer;
+use dom::webglcontextevent::WebGLContextEvent;
 use dom::webglframebuffer::WebGLFramebuffer;
 use dom::webglprogram::WebGLProgram;
 use dom::webglrenderbuffer::WebGLRenderbuffer;
@@ -115,6 +117,15 @@ impl WebGLRenderingContext {
                                                WebGLRenderingContextBinding::Wrap)),
             Err(msg) => {
                 error!("Couldn't create WebGLRenderingContext: {}", msg);
+                let event = WebGLContextEvent::new(global, "webglcontextcreationerror".to_owned(),
+                                                   EventBubbles::DoesNotBubble,
+                                                   EventCancelable::Cancelable,
+                                                   msg);
+
+                let event = EventCast::from_ref(event.r());
+                let target = EventTargetCast::from_ref(canvas);
+
+                event.fire(target);
                 None
             }
         }

components/script/dom/webidls/WebGLContextEvent.webidl

@@ -0,0 +1,15 @@
+/* -*- Mode: IDL; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * 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/. */
+
+// https://www.khronos.org/registry/webgl/specs/latest/1.0/#5.15
+[Constructor(DOMString type, optional WebGLContextEventInit eventInit)]
+interface WebGLContextEvent : Event {
+    readonly attribute DOMString statusMessage;
+};
+
+// https://www.khronos.org/registry/webgl/specs/latest/1.0/#5.15
+dictionary WebGLContextEventInit : EventInit {
+    DOMString statusMessage;
+};