Auto merge of #18093 - pyfisch:compositionevent, r=jdm

Add CompositionEvent bindings

<!-- Please describe your changes on the following line: -->
Needed for better keyboard input. See also #17578

---
<!-- Thank you for contributing to Servo! Please replace each `[ ]` by `[X]` when the step is complete, and replace `__` with appropriate data: -->
- [ ] `./mach build -d` does not report any errors
- [ ] `./mach test-tidy` does not report any errors
- [ ] These changes fix #__ (github issue number if applicable).

<!-- Either: -->
- [ ] There are tests for these changes OR
- [ ] These changes do not require tests because _____

<!-- Also, please make sure that "Allow edits from maintainers" checkbox is checked, so that we can help you if you get stuck somewhere along the way.-->

<!-- Pull requests that do not address these steps are welcome, but they will require additional verification as part of the review process. -->

<!-- Reviewable:start -->
---
This change is [<img src="https://reviewable.io/review_button.svg" height="34" align="absmiddle" alt="Reviewable"/>](https://reviewable.io/reviews/servo/servo/18093)
<!-- Reviewable:end -->

components/script/dom/compositionevent.rs

@@ -0,0 +1,64 @@
+/* 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::CompositionEventBinding::{self, CompositionEventMethods};
+use dom::bindings::codegen::Bindings::UIEventBinding::UIEventBinding::UIEventMethods;
+use dom::bindings::error::Fallible;
+use dom::bindings::js::{Root, RootedReference};
+use dom::bindings::reflector::reflect_dom_object;
+use dom::bindings::str::DOMString;
+use dom::uievent::UIEvent;
+use dom::window::Window;
+use dom_struct::dom_struct;
+
+#[dom_struct]
+pub struct CompositionEvent {
+    uievent: UIEvent,
+    data: DOMString,
+}
+
+impl CompositionEvent {
+    pub fn new(window: &Window,
+               type_: DOMString,
+               can_bubble: bool,
+               cancelable: bool,
+               view: Option<&Window>,
+               detail: i32,
+               data: DOMString) -> Root<CompositionEvent> {
+        let ev = reflect_dom_object(box CompositionEvent {
+                                        uievent: UIEvent::new_inherited(),
+                                        data: data,
+                                    },
+                                    window,
+                                    CompositionEventBinding::Wrap);
+        ev.uievent.InitUIEvent(type_, can_bubble, cancelable, view, detail);
+        ev
+    }
+
+    pub fn Constructor(window: &Window,
+                       type_: DOMString,
+                       init: &CompositionEventBinding::CompositionEventInit)
+                       -> Fallible<Root<CompositionEvent>> {
+        let event = CompositionEvent::new(window,
+                                    type_,
+                                    init.parent.parent.bubbles,
+                                    init.parent.parent.cancelable,
+                                    init.parent.view.r(),
+                                    init.parent.detail,
+                                    init.data.clone());
+        Ok(event)
+    }
+}
+
+impl CompositionEventMethods for CompositionEvent {
+    // https://w3c.github.io/uievents/#dom-compositionevent-data
+    fn Data(&self) -> DOMString {
+        self.data.clone()
+    }
+
+    // https://dom.spec.whatwg.org/#dom-event-istrusted
+    fn IsTrusted(&self) -> bool {
+        self.uievent.IsTrusted()
+    }
+}

components/script/dom/mod.rs

@@ -236,6 +236,7 @@ pub mod characterdata;
 pub mod client;
 pub mod closeevent;
 pub mod comment;
+pub mod compositionevent;
 pub mod console;
 mod create;
 pub mod crypto;

components/script/dom/webidls/CompositionEvent.webidl

@@ -0,0 +1,20 @@
+/* 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/. */
+/*
+ * The origin of this IDL file is
+ * https://w3c.github.io/uievents/#idl-compositionevent
+ *
+ */
+
+// https://w3c.github.io/uievents/#idl-compositionevent
+[Pref="dom.compositionevent.enabled", Constructor(DOMString type, optional CompositionEventInit eventInitDict)]
+interface CompositionEvent : UIEvent {
+  readonly attribute DOMString data;
+};
+
+// https://w3c.github.io/uievents/#idl-compositioneventinit
+dictionary CompositionEventInit : UIEventInit {
+  DOMString data = "";
+};
+

resources/prefs.json

@@ -1,6 +1,7 @@
 {
   "dom.bluetooth.enabled": false,
   "dom.bluetooth.testing.enabled": false,
+  "dom.compositionevent.enabled": false,
   "dom.customelements.enabled": false,
   "dom.forcetouch.enabled": false,
   "dom.gamepad.enabled": false,