script: Minimize layout queries for window scroll offsets. (#38018)

These changes reduce the number of times we need to query layout for the
same information when creating mouse/pointer events.

Testing: No new tests required for maintaining existing behaviour.

Signed-off-by: Josh Matthews <josh@joshmatthews.net>

components/script/dom/mouseevent.rs

@@ -278,9 +278,10 @@ impl MouseEventMethods<crate::DomTypeHolder> for MouseEvent {
     ) -> Fallible<DomRoot<MouseEvent>> {
         let bubbles = EventBubbles::from(init.parent.parent.parent.bubbles);
         let cancelable = EventCancelable::from(init.parent.parent.parent.cancelable);
+        let scroll_offset = window.scroll_offset(can_gc);
         let page_point = Point2D::new(
-            window.ScrollX() + init.clientX,
+            scroll_offset.x as i32 + init.clientX,
-            window.ScrollY() + init.clientY,
+            scroll_offset.y as i32 + init.clientY,
         );
         let event = MouseEvent::new_with_proto(
             window,
@@ -478,6 +479,7 @@ impl MouseEventMethods<crate::DomTypeHolder> for MouseEvent {
         meta_key_arg: bool,
         button_arg: i16,
         related_target_arg: Option<&EventTarget>,
+        can_gc: CanGc,
     ) {
         if self.upcast::<Event>().dispatching() {
             return;
@@ -496,9 +498,10 @@ impl MouseEventMethods<crate::DomTypeHolder> for MouseEvent {
             .set(Point2D::new(client_x_arg, client_y_arg));
 
         let global = self.global();
+        let scroll_offset = global.as_window().scroll_offset(can_gc);
         self.page_point.set(Point2D::new(
-            global.as_window().ScrollX() + client_x_arg,
+            scroll_offset.x as i32 + client_x_arg,
-            global.as_window().ScrollY() + client_y_arg,
+            scroll_offset.y as i32 + client_y_arg,
         ));
 
         let mut modifiers = Modifiers::empty();

components/script/dom/pointerevent.rs

@@ -8,7 +8,6 @@ use dom_struct::dom_struct;
 use euclid::Point2D;
 use js::rust::HandleObject;
 use keyboard_types::Modifiers;
-use script_bindings::codegen::GenericBindings::WindowBinding::WindowMethods;
 use style_traits::CSSPixel;
 
 use super::bindings::codegen::Bindings::MouseEventBinding::MouseEventMethods;
@@ -234,9 +233,10 @@ impl PointerEventMethods<crate::DomTypeHolder> for PointerEvent {
     ) -> DomRoot<PointerEvent> {
         let bubbles = EventBubbles::from(init.parent.parent.parent.parent.bubbles);
         let cancelable = EventCancelable::from(init.parent.parent.parent.parent.cancelable);
+        let scroll_offset = window.scroll_offset(can_gc);
         let page_point = Point2D::new(
-            window.ScrollX() + init.parent.clientX,
+            scroll_offset.x as i32 + init.parent.clientX,
-            window.ScrollY() + init.parent.clientY,
+            scroll_offset.y as i32 + init.parent.clientY,
         );
         PointerEvent::new_with_proto(
             window,

components/script/dom/wheelevent.rs

@@ -95,6 +95,7 @@ impl WheelEvent {
             delta_y,
             delta_z,
             delta_mode,
+            can_gc,
         );
 
         ev
@@ -160,6 +161,7 @@ impl WheelEventMethods<crate::DomTypeHolder> for WheelEvent {
         delta_y_arg: Finite<f64>,
         delta_z_arg: Finite<f64>,
         delta_mode_arg: u32,
+        can_gc: CanGc,
     ) {
         if self.upcast::<Event>().dispatching() {
             return;
@@ -181,6 +183,7 @@ impl WheelEventMethods<crate::DomTypeHolder> for WheelEvent {
             self.mouseevent.MetaKey(),
             self.mouseevent.Button(),
             self.mouseevent.GetRelatedTarget().as_deref(),
+            can_gc,
         );
         self.delta_x.set(delta_x_arg);
         self.delta_y.set(delta_y_arg);

components/script/dom/window.rs

@@ -1596,11 +1596,7 @@ impl WindowMethods<crate::DomTypeHolder> for Window {
 
     /// <https://drafts.csswg.org/cssom-view/#dom-window-scrollx>
     fn ScrollX(&self) -> i32 {
-        self.scroll_offset_query_with_external_scroll_id(
+        self.scroll_offset(CanGc::note()).x as i32
-            self.pipeline_id().root_scroll_id(),
-            CanGc::note(),
-        )
-        .x as i32
     }
 
     // https://drafts.csswg.org/cssom-view/#dom-window-pagexoffset
@@ -1610,11 +1606,7 @@ impl WindowMethods<crate::DomTypeHolder> for Window {
 
     /// <https://drafts.csswg.org/cssom-view/#dom-window-scrolly>
     fn ScrollY(&self) -> i32 {
-        self.scroll_offset_query_with_external_scroll_id(
+        self.scroll_offset(CanGc::note()).y as i32
-            self.pipeline_id().root_scroll_id(),
-            CanGc::note(),
-        )
-        .y as i32
     }
 
     // https://drafts.csswg.org/cssom-view/#dom-window-pageyoffset
@@ -1656,10 +1648,11 @@ impl WindowMethods<crate::DomTypeHolder> for Window {
 
     // https://drafts.csswg.org/cssom-view/#dom-window-scrollby
     fn ScrollBy_(&self, x: f64, y: f64, can_gc: CanGc) {
+        let scroll_offset = self.scroll_offset(can_gc);
         // Step 3
-        let left = x + self.ScrollX() as f64;
+        let left = x + scroll_offset.x as f64;
         // Step 4
-        let top = y + self.ScrollY() as f64;
+        let top = y + scroll_offset.y as f64;
 
         // Step 5
         self.scroll(left, top, ScrollBehavior::Auto, can_gc);
@@ -1984,6 +1977,13 @@ impl WindowMethods<crate::DomTypeHolder> for Window {
 }
 
 impl Window {
+    pub(crate) fn scroll_offset(&self, can_gc: CanGc) -> Vector2D<f32, LayoutPixel> {
+        self.scroll_offset_query_with_external_scroll_id(
+            self.pipeline_id().root_scroll_id(),
+            can_gc,
+        )
+    }
+
     // https://heycam.github.io/webidl/#named-properties-object
     // https://html.spec.whatwg.org/multipage/#named-access-on-the-window-object
     #[allow(unsafe_code)]
@@ -2102,7 +2102,8 @@ impl Window {
 
         // Step 10
         //TODO handling ongoing smooth scrolling
-        if x == self.ScrollX() as f64 && y == self.ScrollY() as f64 {
+        let scroll_offset = self.scroll_offset(can_gc);
+        if x == scroll_offset.x as f64 && y == scroll_offset.y as f64 {
             return;
         }
 

components/script_bindings/codegen/Bindings.conf

@@ -488,7 +488,7 @@ DOMInterfaces = {
 },
 
 'MouseEvent': {
-    'canGc': ['OffsetX', 'OffsetY'],
+    'canGc': ['InitMouseEvent', 'OffsetX', 'OffsetY'],
 },
 
 'NavigationPreloadManager': {
@@ -649,6 +649,10 @@ DOMInterfaces = {
     'additionalTraits': ['crate::interfaces::WebGL2RenderingContextHelpers'],
 },
 
+'WheelEvent': {
+    'canGc': ['InitWheelEvent'],
+},
+
 'Window': {
     'canGc': ['Stop', 'Fetch', 'Scroll', 'Scroll_','ScrollBy', 'ScrollBy_', 'Stop', 'Fetch', 'Open', 'CreateImageBitmap', 'CreateImageBitmap_', 'TrustedTypes', 'WebdriverCallback', 'WebdriverException'],
     'inRealms': ['Fetch', 'GetOpener', 'WebdriverCallback', 'WebdriverException'],