Fix invalid index in drop target Grid (#9604)

Was using length - 1 and 0 for getting the row element,
which caused client side exception when dragging over header or footer when the grid had enough rows.
This had no effect on UX, only exceptions thrown. Now using visible range instead.

1 files changed, 15 insertions, 11 deletions

diff --git a/client/src/main/java/com/vaadin/client/connectors/grid/GridDropTargetConnector.java b/client/src/main/java/com/vaadin/client/connectors/grid/GridDropTargetConnector.java
index 9954134821..ae24ed850f 100644
--- a/client/src/main/java/com/vaadin/client/connectors/grid/GridDropTargetConnector.java
+++ b/client/src/main/java/com/vaadin/client/connectors/grid/GridDropTargetConnector.java
@@ -31,6 +31,7 @@ import com.vaadin.client.widget.escalator.RowContainer;
 import com.vaadin.client.widget.escalator.RowContainer.BodyRowContainer;
 import com.vaadin.client.widgets.Escalator;
 import com.vaadin.shared.MouseEventDetails;
+import com.vaadin.shared.Range;
 import com.vaadin.shared.ui.Connect;
 import com.vaadin.shared.ui.grid.DropLocation;
 import com.vaadin.shared.ui.grid.DropMode;
@@ -128,7 +129,7 @@ public class GridDropTargetConnector extends DropTargetExtensionConnector {
      * Get the row data as json object for the given row.
      *
      * @param row
-     *         table row element
+     *            table row element
      * @return row data as json object for the given row
      */
     protected JsonObject getRowData(TableRowElement row) {
@@ -141,9 +142,9 @@ public class GridDropTargetConnector extends DropTargetExtensionConnector {
      * Returns the location of the event within the row.
      *
      * @param target
-     *         drop target element
+     *            drop target element
      * @param event
-     *         drop event
+     *            drop event
      */
     protected DropLocation getDropLocation(Element target, NativeEvent event) {
         if (TableRowElement.is(target)) {
@@ -257,13 +258,13 @@ public class GridDropTargetConnector extends DropTargetExtensionConnector {
      * Gets the target element for a dragover or drop event.
      *
      * @param source
-     *         the event target of the event
+     *            the event target of the event
      * @return the element that should be handled as the target of the event
      */
     protected Element getTargetElement(Element source) {
         final Element tableWrapper = getDropTargetElement();
         final BodyRowContainer gridBody = getGridBody();
-        final int rowCount = gridBody.getRowCount();
+        final Range visibleRowRange = getEscalator().getVisibleRowRange();
 
         while (!Objects.equals(source, tableWrapper)) {
             // the drop might happen on top of header, body or footer rows
@@ -272,20 +273,22 @@ public class GridDropTargetConnector extends DropTargetExtensionConnector {
                 if ("thead".equalsIgnoreCase(parentTagName)) {
                     // for empty grid or ON_TOP mode, drop as last row,
                     // otherwise as above first visible row
-                    if (rowCount == 0
+                    if (visibleRowRange.length() == 0
                             || getState().dropMode == DropMode.ON_TOP) {
                         return tableWrapper;
                     } else {
-                        return gridBody.getRowElement(0);
+                        return gridBody
+                                .getRowElement(visibleRowRange.getStart());
                     }
                 } else if ("tfoot".equalsIgnoreCase(parentTagName)) {
                     // for empty grid or ON_TOP mode, drop as last row,
                     // otherwise as below last visible row
-                    if (rowCount == 0
+                    if (visibleRowRange.length() == 0
                             || getState().dropMode == DropMode.ON_TOP) {
                         return tableWrapper;
                     } else {
-                        return gridBody.getRowElement(rowCount - 1);
+                        return gridBody
+                                .getRowElement(visibleRowRange.getEnd() - 1);
                     }
                 } else { // parent is tbody
                     return source;
@@ -296,11 +299,12 @@ public class GridDropTargetConnector extends DropTargetExtensionConnector {
         // the drag is on top of the tablewrapper
         // if no rows in grid, or if the drop mode is ON_TOP, then there is no
         // target row for the drop
-        if (rowCount == 0 || getState().dropMode == DropMode.ON_TOP) {
+        if (visibleRowRange.length() == 0
+                || getState().dropMode == DropMode.ON_TOP) {
             return tableWrapper;
         } else { // if dragged under the last row to empty space, drop target
                  // needs to be below the last row
-            return gridBody.getRowElement(rowCount - 1);
+            return gridBody.getRowElement(visibleRowRange.getEnd() - 1);
         }
     }