Merge "Fix issue #13366. Take account of stackFromBottom in computeVerticalScrollOffset()."

Author: Jean-Baptiste Queru

core/java/android/widget/GridView.java

@@ -2095,8 +2095,13 @@ protected int computeVerticalScrollOffset() {
             int height = view.getHeight();
             if (height > 0) {
                 final int numColumns = mNumColumns;
-                final int whichRow = mFirstPosition / numColumns;
                 final int rowCount = (mItemCount + numColumns - 1) / numColumns;
+                // In case of stackFromBottom the calculation of whichRow needs
+                // to take into account that counting from the top the first row
+                // might not be entirely filled.
+                final int oddItemsOnFirstRow = isStackFromBottom() ? ((rowCount * numColumns) -
+                        mItemCount) : 0;
+                final int whichRow = (mFirstPosition + oddItemsOnFirstRow) / numColumns;
                 return Math.max(whichRow * 100 - (top * 100) / height +
                         (int) ((float) mScrollY / getHeight() * rowCount * 100), 0);
             }