Guard against incomplete cell measurement

bvaughn · Jan 27, 2019 · a9c2ae7 · a9c2ae7
1 parent 32f3259
commit a9c2ae7
Showing 1 changed file with 7 additions and 0 deletions.
diff --git a/source/Grid/utils/CellSizeAndPositionManager.js b/source/Grid/utils/CellSizeAndPositionManager.js
@@ -246,6 +246,13 @@ export default class CellSizeAndPositionManager {
         return nearestCellIndex;
       }
       nearestCellIndex = vector.indexOf(targetOffset);
+      // Guard in case `getSizeAndPositionOfCell` didn't fully measure to
+      // the nearestCellIndex. This might happen scrolling quickly down
+      // and back up on large lists -- possible race with React or DOM?
+      if (nearestCellIndex === -1) {
+        nearestCellIndex = this._lastMeasuredIndex;
+        this._lastMeasuredIndex = nearestCellIndex - 1;
+      }
     }
 
     return nearestCellIndex;