1 files changed, 29 insertions, 5 deletions

diff --git a/slick.dataview.js b/slick.dataview.js
index 2dabd87..8103714 100644
--- a/slick.dataview.js
+++ b/slick.dataview.js
@@ -304,7 +304,7 @@
     function mapIdsToRows(idArray) {
       var rows = [];
       ensureRowsByIdCache();
-      for (var i = 0; i < idArray.length; i++) {
+      for (var i = 0, l = idArray.length; i < l; i++) {
         var row = rowsById[idArray[i]];
         if (row != null) {
           rows[rows.length] = row;
@@ -315,7 +315,7 @@
 
     function mapRowsToIds(rowArray) {
       var ids = [];
-      for (var i = 0; i < rowArray.length; i++) {
+      for (var i = 0, l = rowArray.length; i < l; i++) {
         if (rowArray[i] < rows.length) {
           ids[ids.length] = rows[rowArray[i]][idProperty];
         }
@@ -838,10 +838,26 @@
       }
     }
 
-    function syncGridSelection(grid, preserveHidden) {
+    /***
+     * Wires the grid and the DataView together to keep row selection tied to item ids.
+     * This is useful since, without it, the grid only knows about rows, so if the items
+     * move around, the same rows stay selected instead of the selection moving along
+     * with the items.
+     *
+     * NOTE:  This doesn't work with cell selection model.
+     *
+     * @param grid {Slick.Grid} The grid to sync selection with.
+     * @param preserveHidden {Boolean} Whether to keep selected items that go out of the
+     *     view due to them getting filtered out.
+     * @param preserveHiddenOnSelectionChange {Boolean} Whether to keep selected items
+     *     that are currently out of the view (see preserveHidden) as selected when selection
+     *     changes.
+     * @method syncGridSelection
+     */
+    function syncGridSelection(grid, preserveHidden, preserveHiddenOnSelectionChange) {
       var self = this;
-      var selectedRowIds = self.mapRowsToIds(grid.getSelectedRows());;
       var inHandler;
+      var selectedRowIds = self.mapRowsToIds(grid.getSelectedRows());
 
       function update() {
         if (selectedRowIds.length > 0) {
@@ -857,7 +873,15 @@
 
       grid.onSelectedRowsChanged.subscribe(function(e, args) {
         if (inHandler) { return; }
-        selectedRowIds = self.mapRowsToIds(grid.getSelectedRows());
+        var newSelectedRowIds = self.mapRowsToIds(grid.getSelectedRows());
+        if (!preserveHiddenOnSelectionChange || !grid.getOptions().multiSelect) {
+          selectedRowIds = newSelectedRowIds;
+        } else {
+          // keep the ones that are hidden
+          selectedRowIds = $.grep(selectedRowIds, function(id) { return self.getRowById(id) === undefined; });
+          // add the newly selected ones
+          selectedRowIds = selectedRowIds.concat(newSelectedRowIds);
+        }
       });
 
       this.onRowsChanged.subscribe(update);