libservo|compositor: Have scroll offset directionality match that of WebRender and the web (#37752)

Previously, our Servo-specific spatial tree scroll offsets were opposite
to
that of WebRender and also the web platform. This is due to the fact,
likely, that `winit` wheel directionality is also flipped. This change
has both the Servo spatial tree and the API take offsets that are
consistent with the web.

Any possible changes to the meaning of wheel directionality will be
handled in a followup change.

This is a breaking change to the Servo API.

Testing: This change updates unit tests.

Signed-off-by: Martin Robinson <mrobinson@igalia.com>
Co-authored-by: Oriol Brufau <obrufau@igalia.com>

ports/servoshell/desktop/app_state.rs

@@ -361,14 +361,14 @@ impl RunningAppState {
             .shortcut(Modifiers::empty(), Key::PageDown, || {
                 let scroll_location = ScrollLocation::Delta(Vector2D::new(
                     0.0,
-                    -self.inner().window.page_height() + 2.0 * LINE_HEIGHT,
+                    self.inner().window.page_height() - 2.0 * LINE_HEIGHT,
                 ));
                 webview.notify_scroll_event(scroll_location, origin);
             })
             .shortcut(Modifiers::empty(), Key::PageUp, || {
                 let scroll_location = ScrollLocation::Delta(Vector2D::new(
                     0.0,
-                    self.inner().window.page_height() - 2.0 * LINE_HEIGHT,
+                    -self.inner().window.page_height() + 2.0 * LINE_HEIGHT,
                 ));
                 webview.notify_scroll_event(scroll_location, origin);
             })
@@ -379,19 +379,19 @@ impl RunningAppState {
                 webview.notify_scroll_event(ScrollLocation::End, origin);
             })
             .shortcut(Modifiers::empty(), Key::ArrowUp, || {
-                let location = ScrollLocation::Delta(Vector2D::new(0.0, 3.0 * LINE_HEIGHT));
-                webview.notify_scroll_event(location, origin);
-            })
-            .shortcut(Modifiers::empty(), Key::ArrowDown, || {
                 let location = ScrollLocation::Delta(Vector2D::new(0.0, -3.0 * LINE_HEIGHT));
                 webview.notify_scroll_event(location, origin);
             })
+            .shortcut(Modifiers::empty(), Key::ArrowDown, || {
+                let location = ScrollLocation::Delta(Vector2D::new(0.0, 3.0 * LINE_HEIGHT));
+                webview.notify_scroll_event(location, origin);
+            })
             .shortcut(Modifiers::empty(), Key::ArrowLeft, || {
-                let location = ScrollLocation::Delta(Vector2D::new(LINE_HEIGHT, 0.0));
+                let location = ScrollLocation::Delta(Vector2D::new(-LINE_HEIGHT, 0.0));
                 webview.notify_scroll_event(location, origin);
             })
             .shortcut(Modifiers::empty(), Key::ArrowRight, || {
-                let location = ScrollLocation::Delta(Vector2D::new(-LINE_HEIGHT, 0.0));
+                let location = ScrollLocation::Delta(Vector2D::new(LINE_HEIGHT, 0.0));
                 webview.notify_scroll_event(location, origin);
             });
     }

ports/servoshell/desktop/headed_window.rs

@@ -630,10 +630,9 @@ impl WindowPortsMethods for Window {
                     dy = 0.0;
                 }
 
-                let scroll_location = ScrollLocation::Delta(Vector2D::new(dx as f32, dy as f32));
-
                 // Send events
                 webview.notify_input_event(InputEvent::Wheel(WheelEvent::new(delta, point)));
+                let scroll_location = ScrollLocation::Delta(-Vector2D::new(dx as f32, dy as f32));
                 webview.notify_scroll_event(scroll_location, point.to_i32());
             },
             WindowEvent::Touch(touch) => {

ports/servoshell/egl/android.rs

@@ -244,32 +244,6 @@ pub extern "C" fn Java_org_servo_servoview_JNIServo_goForward<'local>(
     call(&mut env, |s| s.go_forward());
 }
 
-#[unsafe(no_mangle)]
-pub extern "C" fn Java_org_servo_servoview_JNIServo_scrollStart<'local>(
-    mut env: JNIEnv<'local>,
-    _: JClass<'local>,
-    dx: jint,
-    dy: jint,
-    x: jint,
-    y: jint,
-) {
-    debug!("scrollStart");
-    call(&mut env, |s| s.scroll_start(dx as f32, dy as f32, x, y));
-}
-
-#[unsafe(no_mangle)]
-pub extern "C" fn Java_org_servo_servoview_JNIServo_scrollEnd<'local>(
-    mut env: JNIEnv<'local>,
-    _: JClass<'local>,
-    dx: jint,
-    dy: jint,
-    x: jint,
-    y: jint,
-) {
-    debug!("scrollEnd");
-    call(&mut env, |s| s.scroll_end(dx as f32, dy as f32, x, y));
-}
-
 #[unsafe(no_mangle)]
 pub extern "C" fn Java_org_servo_servoview_JNIServo_scroll<'local>(
     mut env: JNIEnv<'local>,

ports/servoshell/egl/app_state.rs

@@ -474,18 +474,6 @@ impl RunningAppState {
         self.perform_updates();
     }
 
-    /// Start scrolling.
-    /// x/y are scroll coordinates.
-    /// dx/dy are scroll deltas.
-    #[cfg(not(target_env = "ohos"))]
-    pub fn scroll_start(&self, dx: f32, dy: f32, x: i32, y: i32) {
-        let delta = Vector2D::new(dx, dy);
-        let scroll_location = ScrollLocation::Delta(delta);
-        self.active_webview()
-            .notify_scroll_event(scroll_location, Point2D::new(x, y));
-        self.perform_updates();
-    }
-
     /// Scroll.
     /// x/y are scroll coordinates.
     /// dx/dy are scroll deltas.
@@ -497,18 +485,6 @@ impl RunningAppState {
         self.perform_updates();
     }
 
-    /// End scrolling.
-    /// x/y are scroll coordinates.
-    /// dx/dy are scroll deltas.
-    #[cfg(not(target_env = "ohos"))]
-    pub fn scroll_end(&self, dx: f32, dy: f32, x: i32, y: i32) {
-        let delta = Vector2D::new(dx, dy);
-        let scroll_location = ScrollLocation::Delta(delta);
-        self.active_webview()
-            .notify_scroll_event(scroll_location, Point2D::new(x, y));
-        self.perform_updates();
-    }
-
     /// Touch event: press down
     pub fn touch_down(&self, x: f32, y: f32, pointer_id: i32) {
         self.active_webview()