minor fixes

com.unity.uiwidgets/Runtime/engine2/UIWidgetsPanel.cs

 
         void _onScroll() {
             var pos = _getPointerPosition(Input.mousePosition);
-            if (pos == null) {
-                return;
-            }
-            var delta = Input.mouseScrollDelta;
-            UIWidgetsPanel_onScroll(_ptr, delta.x, delta.y, pos.Value.x, pos.Value.y);
+            _wrapper.OnMouseScroll(Input.mouseScrollDelta, pos);
         }
 
         public void OnPointerDown(PointerEventData eventData) {

com.unity.uiwidgets/Runtime/engine2/UIWidgetsPanelWrapper.cs

         UIWidgetsPanel_onMouseMove(_ptr, pos.Value.x, pos.Value.y);
     }
 
+    public void OnMouseScroll(Vector2 delta, Vector2? pos) {
+        if (pos == null) {
+            return;
+        }
+        UIWidgetsPanel_onScroll(_ptr, delta.x, delta.y, pos.Value.x, pos.Value.y);
+    }
+
     public void OnPointerDown(Vector2? pos, int pointerId) {
         if (pos == null) {
             return;
 
     [DllImport(NativeBindings.dllName)]
     static extern void UIWidgetsPanel_onMouseLeave(IntPtr ptr);
+    
+    [DllImport(NativeBindings.dllName)]
+    static extern void UIWidgetsPanel_onScroll(IntPtr ptr, float x, float y, float px, float py);
 }
 
 #endregion

engine/src/shell/platform/unity/windows/uiwidgets_panel.cc

 
   //_Wait
   panel->ProcessMessages();
+}
 
 UIWIDGETS_API(void)
 UIWidgetsPanel_onScroll(UIWidgetsPanel* panel, float x, float y, float px, float py) {