revert scroll position changes

Author: vursen

packages/grid/src/vaadin-grid-drag-and-drop-mixin.js

@@ -248,7 +248,7 @@ export const DragAndDropMixin = (superClass) =>
         let row = e.composedPath().find((node) => node.localName === 'tr');
 
         // Update the horizontal scroll position property of the row being dragged over
-        // this.__updateRowScrollPositionProperty(row);
+        this.__updateRowScrollPositionProperty(row);
 
         if (!this._flatSize || this.dropMode === DropMode.ON_GRID) {
           // The grid is empty or "on-grid" drop mode was used, always default to "empty"

packages/grid/src/vaadin-grid-scroll-mixin.js

@@ -449,7 +449,26 @@ export const ScrollMixin = (superClass) =>
         }
       });
 
-      this.$.table.style.setProperty('--_grid-horizontal-scroll-position', `${this.__horizontalScrollPosition}px`);
+      const focusedRow = this.shadowRoot.querySelector("[part~='row']:focus");
+      if (focusedRow) {
+        // Update the horizontal scroll position property of the focused row
+        this.__updateRowScrollPositionProperty(focusedRow);
+      }
+    }
+
+    /**
+     * Synchronizes the internal `--_grid-horizontal-scroll-position` CSS property
+     * of the given row with the current horizontal scroll position of the grid.
+     * @private
+     */
+    __updateRowScrollPositionProperty(row) {
+      if (row instanceof HTMLTableRowElement === false) {
+        return;
+      }
+      const newValue = `${this.__horizontalScrollPosition}px`;
+      if (row.style.getPropertyValue('--_grid-horizontal-scroll-position') !== newValue) {
+        row.style.setProperty('--_grid-horizontal-scroll-position', newValue);
+      }
     }
 
     /** @private */