Add public methods for animation

source/Grid/Grid.jest.js

@@ -366,6 +366,35 @@ describe('Grid', () => {
       expect(grid.state.scrollTop).toEqual(900)
     })
 
+    it('should support scrollToPosition() public method', () => {
+      const grid = render(getMarkup())
+      expect(grid.state.scrollLeft).toEqual(0)
+      expect(grid.state.scrollTop).toEqual(0)
+
+      grid.scrollToPosition({
+        scrollLeft: 50,
+        scrollTop: 50
+      })
+      expect(grid.state.scrollLeft).toEqual(50)
+      expect(grid.state.scrollTop).toEqual(50)
+    })
+
+    it('should support getOffsetForCell() public method', () => {
+      const grid = render(getMarkup())
+      const { scrollLeft, scrollTop } = grid.getOffsetForCell({
+        columnIndex: 24,
+        rowIndex: 49
+      })
+      // 100 columns * 50 item width = 5,000 total item width
+      // 4 columns can be visible at a time and :scrollLeft is initially 0,
+      // So the minimum amount of scrolling leaves the 25th item at the right (just scrolled into view).
+      expect(scrollLeft).toEqual(1050)
+      // 100 rows * 20 item height = 2,000 total item height
+      // 5 rows can be visible at a time and :scrollTop is initially 0,
+      // So the minimum amount of scrolling leaves the 50th item at the bottom (just scrolled into view).
+      expect(scrollTop).toEqual(900)
+    })
+
     // See issue #565
     it('should update scroll position to account for changed cell sizes within a function prop wrapper', () => {
       let rowHeight = 20

source/Grid/Grid.js

@@ -264,8 +264,6 @@ export default class Grid extends PureComponent {
     this._invokeOnGridRenderedHelper = this._invokeOnGridRenderedHelper.bind(this)
     this._onScroll = this._onScroll.bind(this)
     this._setScrollingContainerRef = this._setScrollingContainerRef.bind(this)
-    this._updateScrollLeftForScrollToColumn = this._updateScrollLeftForScrollToColumn.bind(this)
-    this._updateScrollTopForScrollToRow = this._updateScrollTopForScrollToRow.bind(this)
 
     this._columnWidthGetter = this._wrapSizeGetter(props.columnWidth)
     this._rowHeightGetter = this._wrapSizeGetter(props.rowHeight)
@@ -381,6 +379,40 @@ export default class Grid extends PureComponent {
     })
   }
 
+  /**
+   * Ensure offset position is visible
+   * Useful for animating position changes
+   */
+  scrollToPosition ({
+    scrollLeft,
+    scrollTop
+  } = {}) {
+    this._setScrollPosition({ scrollLeft, scrollTop })
+  }
+
+  /**
+   * Gets offsets for a given cell and alignment
+   */
+  getOffsetForCell ({
+    columnIndex,
+    rowIndex,
+    scrollToAlignment = this.props.scrollToAlignment
+  } = {}) {
+    const scrollToColumn = columnIndex >= 0 ? columnIndex : this.props.scrollToColumn
+    const scrollToRow = rowIndex >= 0 ? rowIndex : this.props.scrollToRow
+    const offsetProps = {
+      ...this.props,
+      scrollToColumn,
+      scrollToRow,
+      scrollToAlignment
+    }
+
+    return {
+      scrollLeft: this._getCalculatedScrollLeft(offsetProps),
+      scrollTop: this._getCalculatedScrollTop(offsetProps)
+    }
+  }
+
   componentDidMount () {
     const { getScrollbarSize, scrollLeft, scrollToColumn, scrollTop, scrollToRow } = this.props
 
@@ -999,7 +1031,7 @@ export default class Grid extends PureComponent {
     return this._wrapPropertyGetter(size)
   }
 
-  _updateScrollLeftForScrollToColumn (props = this.props, state = this.state) {
+  _getCalculatedScrollLeft (props = this.props, state = this.state) {
     const { columnCount, height, scrollToAlignment, scrollToColumn, width } = props
     const { scrollLeft } = state
 
@@ -1008,22 +1040,27 @@ export default class Grid extends PureComponent {
       const totalRowsHeight = this._rowSizeAndPositionManager.getTotalSize()
       const scrollBarSize = totalRowsHeight > height ? this._scrollbarSize : 0
 
-      const calculatedScrollLeft = this._columnSizeAndPositionManager.getUpdatedOffsetForIndex({
+      return this._columnSizeAndPositionManager.getUpdatedOffsetForIndex({
         align: scrollToAlignment,
         containerSize: width - scrollBarSize,
         currentOffset: scrollLeft,
         targetIndex
       })
+    }
+  }
 
-      if (scrollLeft !== calculatedScrollLeft) {
-        this._setScrollPosition({
-          scrollLeft: calculatedScrollLeft
-        })
-      }
+  _updateScrollLeftForScrollToColumn (props = this.props, state = this.state) {
+    const { scrollLeft } = state
+    const calculatedScrollLeft = this._getCalculatedScrollLeft(props, state)
+
+    if (calculatedScrollLeft >= 0 && scrollLeft !== calculatedScrollLeft) {
+      this._setScrollPosition({
+        scrollLeft: calculatedScrollLeft
+      })
     }
   }
 
-  _updateScrollTopForScrollToRow (props = this.props, state = this.state) {
+  _getCalculatedScrollTop (props = this.props, state = this.state) {
     const { height, rowCount, scrollToAlignment, scrollToRow, width } = props
     const { scrollTop } = state
 
@@ -1032,18 +1069,23 @@ export default class Grid extends PureComponent {
       const totalColumnsWidth = this._columnSizeAndPositionManager.getTotalSize()
       const scrollBarSize = totalColumnsWidth > width ? this._scrollbarSize : 0
 
-      const calculatedScrollTop = this._rowSizeAndPositionManager.getUpdatedOffsetForIndex({
+      return this._rowSizeAndPositionManager.getUpdatedOffsetForIndex({
         align: scrollToAlignment,
         containerSize: height - scrollBarSize,
         currentOffset: scrollTop,
         targetIndex
       })
+    }
+  }
 
-      if (scrollTop !== calculatedScrollTop) {
-        this._setScrollPosition({
-          scrollTop: calculatedScrollTop
-        })
-      }
+  _updateScrollTopForScrollToRow (props = this.props, state = this.state) {
+    const { scrollTop } = state
+    const calculatedScrollTop = this._getCalculatedScrollTop(props, state)
+
+    if (calculatedScrollTop >= 0 && scrollTop !== calculatedScrollTop) {
+      this._setScrollPosition({
+        scrollTop: calculatedScrollTop
+      })
     }
   }
 

source/List/List.js

@@ -122,6 +122,19 @@ export default class List extends PureComponent {
     })
   }
 
+  /** See Grid#getOffsetForCell */
+  getOffsetForRow ({
+    rowIndex,
+    scrollToAlignment
+  }) {
+    const { scrollTop } = this.Grid.getOffsetForCell({
+      columnIndex: 0,
+      rowIndex,
+      scrollToAlignment
+    })
+    return scrollTop
+  }
+
   /** See Grid#scrollToCell */
   scrollToRow (index = 0) {
     this.Grid.scrollToCell({
@@ -130,6 +143,11 @@ export default class List extends PureComponent {
     })
   }
 
+  /** See Grid#scrollToPosition */
+  scrollToPosition (scrollTop = 0) {
+    this.Grid.scrollToPosition({ scrollTop })
+  }
+
   render () {
     const {
       className,