fix for #998

source/Grid/Grid.jest.js

@@ -637,6 +637,87 @@ describe('Grid', () => {
       expect(node.scrollTop).toBe(1920);
     });
 
+    // See issue #998
+    it('call to recomputeGridSize should not reset position to scrollTo[Row|Column] when scrolling forward', () => {
+      const cellRendererCalls = [];
+      function cellRenderer({columnIndex, key, rowIndex, style}) {
+        cellRendererCalls.push({columnIndex, rowIndex});
+        return defaultCellRenderer({columnIndex, key, rowIndex, style});
+      }
+      const props = {
+        cellRenderer,
+        columnWidth: 100,
+        height: 40,
+        rowHeight: 20,
+        scrollToRow: 0,
+        scrollToColumn: 0,
+        width: 100,
+      };
+
+      const grid = render(getMarkup(props));
+      expect(cellRendererCalls).toEqual([
+        {columnIndex: 0, rowIndex: 0},
+        {columnIndex: 0, rowIndex: 1},
+      ]);
+
+      //scroll forward to row 45
+      simulateScroll({grid, scrollTop: 900, scrollLeft: 2400});
+
+      expect(grid.state.scrollDirectionVertical).toEqual(
+        SCROLL_DIRECTION_FORWARD,
+      );
+      cellRendererCalls.splice(0);
+
+      grid.recomputeGridSize({rowIndex: 45, columnIndex: 24});
+
+      //grid should still be at row 45, column 24
+      expect(cellRendererCalls).toEqual([
+        {columnIndex: 24, rowIndex: 45},
+        {columnIndex: 24, rowIndex: 46},
+      ]);
+    });
+    // see #998
+    it('call to recomputeGridSize should not reset position to scrollTo[Row|Column] when scrolling backward', () => {
+      const cellRendererCalls = [];
+      function cellRenderer({columnIndex, key, rowIndex, style}) {
+        cellRendererCalls.push({columnIndex, rowIndex});
+        return defaultCellRenderer({columnIndex, key, rowIndex, style});
+      }
+      const props = {
+        cellRenderer,
+        columnWidth: 100,
+        height: 40,
+        rowHeight: 20,
+        scrollToRow: 99,
+        scrollToColumn: 49,
+        width: 100,
+      };
+
+      const grid = render(getMarkup(props));
+      expect(cellRendererCalls).toEqual([
+        {columnIndex: 0, rowIndex: 0},
+        {columnIndex: 0, rowIndex: 1},
+        {columnIndex: 49, rowIndex: 98},
+        {columnIndex: 49, rowIndex: 99},
+      ]);
+
+      //scroll backward to row 45
+      simulateScroll({grid, scrollTop: 900, scrollLeft: 2400});
+
+      expect(grid.state.scrollDirectionVertical).toEqual(
+        SCROLL_DIRECTION_BACKWARD,
+      );
+      cellRendererCalls.splice(0);
+
+      grid.recomputeGridSize({rowIndex: 45, columnIndex: 24});
+
+      //grid should still be at row 45 and column 24
+      expect(cellRendererCalls).toEqual([
+        {columnIndex: 24, rowIndex: 45},
+        {columnIndex: 24, rowIndex: 46},
+      ]);
+    });
+
     it('should restore scroll offset for column when row count increases from 0 (and vice versa)', () => {
       const props = {
         columnWidth: 50,

source/Grid/Grid.js

@@ -480,8 +480,16 @@ export default class Grid extends React.PureComponent<Props, State> {
     // In this case the cDU handler can't know if they changed.
     // Store this flag to let the next cDU pass know it needs to recompute the scroll offset.
     this._recomputeScrollLeftFlag =
-      scrollToColumn >= 0 && columnIndex <= scrollToColumn;
-    this._recomputeScrollTopFlag = scrollToRow >= 0 && rowIndex <= scrollToRow;
+      scrollToColumn >= 0 &&
+      (this.state.scrollDirectionHorizontal === SCROLL_DIRECTION_FORWARD
+        ? columnIndex <= scrollToColumn
+        : columnIndex >= scrollToColumn);
+
+    this._recomputeScrollTopFlag =
+      scrollToRow >= 0 &&
+      (this.state.scrollDirectionVertical === SCROLL_DIRECTION_FORWARD
+        ? rowIndex <= scrollToRow
+        : rowIndex >= scrollToRow);
 
     // Clear cell cache in case we are scrolling;
     // Invalid row heights likely mean invalid cached content as well.