Implement MouseEvent buttons attribute

components/compositing/compositor.rs

@@ -662,6 +662,7 @@ impl<Window: WindowMethods + ?Sized> IOCompositor<Window> {
             result.point_in_viewport.to_untyped(),
             Some(UntrustedNodeAddress(result.tag.0 as *const c_void)),
             Some(result.point_relative_to_item.to_untyped()),
+            MouseButton::Left as u16,
         );
 
         let pipeline_id = PipelineId::from_webrender(result.pipeline);
@@ -705,7 +706,11 @@ impl<Window: WindowMethods + ?Sized> IOCompositor<Window> {
         let results = self.hit_test_at_point(cursor);
         if let Some(item) = results.items.first() {
             let node_address = Some(UntrustedNodeAddress(item.tag.0 as *const c_void));
-            let event = MouseMoveEvent(Some(item.point_in_viewport.to_untyped()), node_address);
+            let event = MouseMoveEvent(
+                Some(item.point_in_viewport.to_untyped()),
+                node_address,
+                MouseButton::Left as u16,
+            );
             let pipeline_id = PipelineId::from_webrender(item.pipeline);
             let msg = ConstellationMsg::ForwardEvent(pipeline_id, event);
             if let Err(e) = self.constellation_chan.send(msg) {

components/constellation/constellation.rs

@@ -135,6 +135,8 @@ use net_traits::storage_thread::{StorageThreadMsg, StorageType};
 use net_traits::{self, FetchResponseMsg, IpcSend, ResourceThreads};
 use profile_traits::mem;
 use profile_traits::time;
+use script_traits::CompositorEvent::{MouseButtonEvent, MouseMoveEvent};
+use script_traits::MouseEventType;
 use script_traits::{webdriver_msg, LogEntry, ScriptToConstellationChan, ServiceWorkerMsg};
 use script_traits::{
     AnimationState, AnimationTickType, AuxiliaryBrowsingContextLoadInfo, CompositorEvent,
@@ -373,6 +375,10 @@ pub struct Constellation<Message, LTF, STF> {
 
     /// Navigation requests from script awaiting approval from the embedder.
     pending_approval_navigations: PendingApprovalNavigations,
+
+    /// Bitmask which indicates which combination of mouse buttons are
+    /// currently being pressed.
+    pressed_mouse_buttons: u16,
 }
 
 /// State needed to construct a constellation.
@@ -715,6 +721,7 @@ where
                     webvr_chan: state.webvr_chan,
                     canvas_chan: CanvasPaintThread::start(),
                     pending_approval_navigations: HashMap::new(),
+                    pressed_mouse_buttons: 0,
                 };
 
                 constellation.run();
@@ -1798,6 +1805,34 @@ where
     }
 
     fn forward_event(&mut self, destination_pipeline_id: PipelineId, event: CompositorEvent) {
+        if let MouseButtonEvent(event_type, button, ..) = &event {
+            match event_type {
+                MouseEventType::MouseDown | MouseEventType::Click => {
+                    self.pressed_mouse_buttons |= *button as u16;
+                },
+                MouseEventType::MouseUp => {
+                    self.pressed_mouse_buttons &= !(*button as u16);
+                },
+            }
+        }
+
+        let event = match event {
+            MouseButtonEvent(event_type, button, point, node_address, point_in_node, _) => {
+                MouseButtonEvent(
+                    event_type,
+                    button,
+                    point,
+                    node_address,
+                    point_in_node,
+                    self.pressed_mouse_buttons,
+                )
+            },
+            MouseMoveEvent(point, node_address, _) => {
+                MouseMoveEvent(point, node_address, self.pressed_mouse_buttons)
+            },
+            _ => event,
+        };
+
         let msg = ConstellationControlMsg::SendEvent(destination_pipeline_id, event);
         let result = match self.pipelines.get(&destination_pipeline_id) {
             None => {

components/script/dom/activation.rs

@@ -12,6 +12,7 @@ use crate::dom::mouseevent::MouseEvent;
 use crate::dom::node::window_from_node;
 use crate::dom::window::ReflowReason;
 use script_layout_interface::message::ReflowGoal;
+use script_traits::MouseButton;
 
 /// Trait for elements with defined activation behavior
 pub trait Activatable {
@@ -96,6 +97,7 @@ pub fn synthetic_click_activation(
         alt_key,
         meta_key,
         0,
+        MouseButton::Left as u16,
         None,
         None,
     );

components/script/dom/document.rs

@@ -926,6 +926,7 @@ impl Document {
         mouse_event_type: MouseEventType,
         node_address: Option<UntrustedNodeAddress>,
         point_in_node: Option<Point2D<f32>>,
+        pressed_mouse_buttons: u16,
     ) {
         let mouse_event_type_string = match mouse_event_type {
             MouseEventType::Click => "click".to_owned(),
@@ -976,6 +977,7 @@ impl Document {
             false,
             false,
             0i16,
+            pressed_mouse_buttons,
             None,
             point_in_node,
         );
@@ -1007,14 +1009,19 @@ impl Document {
 
         if let MouseEventType::Click = mouse_event_type {
             self.commit_focus_transaction(FocusType::Element);
-            self.maybe_fire_dblclick(client_point, node);
+            self.maybe_fire_dblclick(client_point, node, pressed_mouse_buttons);
         }
 
         self.window
             .reflow(ReflowGoal::Full, ReflowReason::MouseEvent);
     }
 
-    fn maybe_fire_dblclick(&self, click_pos: Point2D<f32>, target: &Node) {
+    fn maybe_fire_dblclick(
+        &self,
+        click_pos: Point2D<f32>,
+        target: &Node,
+        pressed_mouse_buttons: u16,
+    ) {
         // https://w3c.github.io/uievents/#event-type-dblclick
         let now = Instant::now();
 
@@ -1053,6 +1060,7 @@ impl Document {
                     false,
                     false,
                     0i16,
+                    pressed_mouse_buttons,
                     None,
                     None,
                 );
@@ -1073,6 +1081,7 @@ impl Document {
         client_point: Point2D<f32>,
         target: &EventTarget,
         event_name: FireMouseEventType,
+        pressed_mouse_buttons: u16,
     ) {
         let client_x = client_point.x.to_i32().unwrap_or(0);
         let client_y = client_point.y.to_i32().unwrap_or(0);
@@ -1093,6 +1102,7 @@ impl Document {
             false,
             false,
             0i16,
+            pressed_mouse_buttons,
             None,
             None,
         );
@@ -1107,6 +1117,7 @@ impl Document {
         client_point: Option<Point2D<f32>>,
         prev_mouse_over_target: &MutNullableDom<Element>,
         node_address: Option<UntrustedNodeAddress>,
+        pressed_mouse_buttons: u16,
     ) {
         let client_point = match client_point {
             None => {
@@ -1132,7 +1143,12 @@ impl Document {
             None => return,
         };
 
-        self.fire_mouse_event(client_point, new_target.upcast(), FireMouseEventType::Move);
+        self.fire_mouse_event(
+            client_point,
+            new_target.upcast(),
+            FireMouseEventType::Move,
+            pressed_mouse_buttons,
+        );
 
         // Nothing more to do here, mousemove is sent,
         // and the element under the mouse hasn't changed.
@@ -1165,7 +1181,12 @@ impl Document {
             }
 
             // Remove hover state to old target and its parents
-            self.fire_mouse_event(client_point, old_target.upcast(), FireMouseEventType::Out);
+            self.fire_mouse_event(
+                client_point,
+                old_target.upcast(),
+                FireMouseEventType::Out,
+                pressed_mouse_buttons,
+            );
 
             // TODO: Fire mouseleave here only if the old target is
             // not an ancestor of the new target.
@@ -1184,7 +1205,12 @@ impl Document {
                 element.set_hover_state(true);
             }
 
-            self.fire_mouse_event(client_point, &new_target.upcast(), FireMouseEventType::Over);
+            self.fire_mouse_event(
+                client_point,
+                &new_target.upcast(),
+                FireMouseEventType::Over,
+                pressed_mouse_buttons,
+            );
 
             // TODO: Fire mouseenter here.
         }

components/script/dom/mouseevent.rs

@@ -32,6 +32,7 @@ pub struct MouseEvent {
     alt_key: Cell<bool>,
     meta_key: Cell<bool>,
     button: Cell<i16>,
+    buttons: Cell<u16>,
     related_target: MutNullableDom<EventTarget>,
     point_in_target: Cell<Option<Point2D<f32>>>,
 }
@@ -49,6 +50,7 @@ impl MouseEvent {
             alt_key: Cell::new(false),
             meta_key: Cell::new(false),
             button: Cell::new(0),
+            buttons: Cell::new(0),
             related_target: Default::default(),
             point_in_target: Cell::new(None),
         }
@@ -78,6 +80,7 @@ impl MouseEvent {
         shift_key: bool,
         meta_key: bool,
         button: i16,
+        buttons: u16,
         related_target: Option<&EventTarget>,
         point_in_target: Option<Point2D<f32>>,
     ) -> DomRoot<MouseEvent> {
@@ -99,6 +102,7 @@ impl MouseEvent {
             button,
             related_target,
         );
+        ev.buttons.set(buttons);
         ev.point_in_target.set(point_in_target);
         ev
     }
@@ -126,6 +130,7 @@ impl MouseEvent {
             init.parent.shiftKey,
             init.parent.metaKey,
             init.button,
+            0,
             init.relatedTarget.deref(),
             None,
         );
@@ -183,6 +188,11 @@ impl MouseEventMethods for MouseEvent {
         self.button.get()
     }
 
+    // https://w3c.github.io/uievents/#dom-mouseevent-buttons
+    fn Buttons(&self) -> u16 {
+        self.buttons.get()
+    }
+
     // https://w3c.github.io/uievents/#widl-MouseEvent-relatedTarget
     fn GetRelatedTarget(&self) -> Option<DomRoot<EventTarget>> {
         self.related_target.get()

components/script/dom/webidls/MouseEvent.webidl

@@ -17,7 +17,7 @@ interface MouseEvent : UIEvent {
     readonly    attribute short          button;
     readonly    attribute EventTarget?   relatedTarget;
     // Introduced in DOM Level 3
-    //readonly    attribute unsigned short buttons;
+    readonly    attribute unsigned short buttons;
     //boolean getModifierState (DOMString keyArg);
 
     [Pref="dom.mouseevent.which.enabled"]
@@ -31,7 +31,7 @@ dictionary MouseEventInit : EventModifierInit {
     long           clientX = 0;
     long           clientY = 0;
     short          button = 0;
-    //unsigned short buttons = 0;
+    unsigned short buttons = 0;
     EventTarget?   relatedTarget = null;
 };
 

components/script/script_thread.rs

@@ -3060,7 +3060,14 @@ impl ScriptThread {
                 self.handle_resize_event(pipeline_id, new_size, size_type);
             },
 
-            MouseButtonEvent(event_type, button, point, node_address, point_in_node) => {
+            MouseButtonEvent(
+                event_type,
+                button,
+                point,
+                node_address,
+                point_in_node,
+                pressed_mouse_buttons,
+            ) => {
                 self.handle_mouse_event(
                     pipeline_id,
                     event_type,
@@ -3068,10 +3075,11 @@ impl ScriptThread {
                     point,
                     node_address,
                     point_in_node,
+                    pressed_mouse_buttons,
                 );
             },
 
-            MouseMoveEvent(point, node_address) => {
+            MouseMoveEvent(point, node_address, pressed_mouse_buttons) => {
                 let document = match { self.documents.borrow().find_document(pipeline_id) } {
                     Some(document) => document,
                     None => return warn!("Message sent to closed pipeline {}.", pipeline_id),
@@ -3086,6 +3094,7 @@ impl ScriptThread {
                     point,
                     &self.topmost_mouse_over_target,
                     node_address,
+                    pressed_mouse_buttons,
                 );
 
                 // Short-circuit if nothing changed
@@ -3185,6 +3194,7 @@ impl ScriptThread {
         point: Point2D<f32>,
         node_address: Option<UntrustedNodeAddress>,
         point_in_node: Option<Point2D<f32>>,
+        pressed_mouse_buttons: u16,
     ) {
         let document = match { self.documents.borrow().find_document(pipeline_id) } {
             Some(document) => document,
@@ -3197,6 +3207,7 @@ impl ScriptThread {
             mouse_event_type,
             node_address,
             point_in_node,
+            pressed_mouse_buttons,
         );
     }
 

components/script_traits/lib.rs

@@ -444,11 +444,11 @@ pub struct TouchId(pub i32);
 #[derive(Clone, Copy, Debug, Deserialize, Serialize)]
 pub enum MouseButton {
     /// The left mouse button.
-    Left,
+    Left = 1,
-    /// The middle mouse button.
-    Middle,
     /// The right mouse button.
-    Right,
+    Right = 2,
+    /// The middle mouse button.
+    Middle = 4,
 }
 
 /// The types of mouse events
@@ -474,9 +474,16 @@ pub enum CompositorEvent {
         Point2D<f32>,
         Option<UntrustedNodeAddress>,
         Option<Point2D<f32>>,
+        // Bitmask of MouseButton values representing the currently pressed buttons
+        u16,
     ),
     /// The mouse was moved over a point (or was moved out of the recognizable region).
-    MouseMoveEvent(Option<Point2D<f32>>, Option<UntrustedNodeAddress>),
+    MouseMoveEvent(
+        Option<Point2D<f32>>,
+        Option<UntrustedNodeAddress>,
+        // Bitmask of MouseButton values representing the currently pressed buttons
+        u16,
+    ),
     /// A touch event was generated with a touch ID and location.
     TouchEvent(
         TouchEventType,

tests/wpt/metadata/dom/events/Event-subclasses-constructors.html.ini

@@ -1,20 +1,5 @@
 [Event-subclasses-constructors.html]
   type: testharness
-  [MouseEvent constructor (no argument)]
-    expected: FAIL
-
-  [MouseEvent constructor (undefined argument)]
-    expected: FAIL
-
-  [MouseEvent constructor (null argument)]
-    expected: FAIL
-
-  [MouseEvent constructor (empty argument)]
-    expected: FAIL
-
-  [MouseEvent constructor (argument with default values)]
-    expected: FAIL
-
   [MouseEvent constructor (argument with non-default values)]
     expected: FAIL
 

tests/wpt/metadata/uievents/idlharness.window.js.ini

@@ -5,9 +5,6 @@
   [MouseEvent interface: new WheelEvent("event") must inherit property "buttons" with the proper type]
     expected: FAIL
 
-  [MouseEvent interface: new MouseEvent("event") must inherit property "buttons" with the proper type]
-    expected: FAIL
-
   [UIEvent interface: new CompositionEvent("event") must inherit property "view" with the proper type]
     expected: FAIL
 
@@ -152,9 +149,6 @@
   [WheelEvent interface: existence and properties of interface prototype object's @@unscopables property]
     expected: FAIL
 
-  [MouseEvent interface: attribute buttons]
-    expected: FAIL
-
   [MouseEvent interface: new WheelEvent("event") must inherit property "screenY" with the proper type]
     expected: FAIL