fix: issue with windowAsScrollContainer and translation offsets

With the recently introduced change to automatically find the scrolling parent of the SortableContainer (getScrollingParent function), there was an issue introduced where the scrollContainer would resolve to the document.body when using windowAsScrollContainer, and the container scroll offset would be taken into account twice. Normally, we take into account the window scroll position and the scroll container’s scroll position, but in this case they were both the same element.

src/SortableContainer/index.js

@@ -502,20 +502,14 @@ export default function sortableContainer(
 
     animateNodes() {
       const {transitionDuration, hideSortableGhost, onSortOver} = this.props;
+      const {containerScrollDelta, windowScrollDelta} = this;
       const nodes = this.manager.getOrderedRefs();
-      const containerScrollDelta = {
-        left: this.scrollContainer.scrollLeft - this.initialScroll.left,
-        top: this.scrollContainer.scrollTop - this.initialScroll.top,
-      };
       const sortingOffset = {
         left:
           this.offsetEdge.left + this.translate.x + containerScrollDelta.left,
         top: this.offsetEdge.top + this.translate.y + containerScrollDelta.top,
       };
-      const windowScrollDelta = {
-        left: window.pageXOffset - this.initialWindowScroll.left,
-        top: window.pageYOffset - this.initialWindowScroll.top,
-      };
+
       const prevIndex = this.newIndex;
       this.newIndex = null;
 
@@ -745,5 +739,25 @@ export default function sortableContainer(
 
       return this.props.helperContainer || this.document.body;
     }
+
+    get containerScrollDelta() {
+      const {useWindowAsScrollContainer} = this.props;
+
+      if (useWindowAsScrollContainer) {
+        return {left: 0, top: 0};
+      }
+
+      return {
+        left: this.scrollContainer.scrollLeft - this.initialScroll.left,
+        top: this.scrollContainer.scrollTop - this.initialScroll.top,
+      };
+    }
+
+    get windowScrollDelta() {
+      return {
+        left: this.contentWindow.pageXOffset - this.initialWindowScroll.left,
+        top: this.contentWindow.pageYOffset - this.initialWindowScroll.top,
+      };
+    }
   };
 }