Fixes #174. Changing Filter does not undo previously marked items (#186)

This addresses #174 (changing the filter caused marked items to get unmarked) by:

- The input to the cmdlet tracks marked/unmarked items
- The list attached to the listview is now always a copy of the input list, with the filter applied (even if there's no fitler).
- Whenever mark/unmark happens in the listview, the original item in the input list is updated
- On exit, any items in the input list that are marked are provided as output

src/Microsoft.PowerShell.ConsoleGuiTools/ConsoleGui.cs

@@ -22,7 +22,15 @@ internal class ConsoleGui : IDisposable
         private Label _filterLabel;
         private TextField _filterField;
         private ListView _listView;
-        private GridViewDataSource _itemSource;
+        // _inputSource contains the full set of Input data and tracks any items the user
+        // marks. When the cmdlet exits, any marked items are returned. When a filter is 
+        // active, the list view shows a copy of _inputSource that includes both the items
+        // matching the filter AND any items previously marked. 
+        private GridViewDataSource _inputSource;
+
+        // _listViewSource is a filtered copy of _inputSource that ListView.Source is set to. 
+        // Changes to IsMarked are propogated back to _inputSource.
+        private GridViewDataSource _listViewSource;
         private ApplicationData _applicationData;
         private GridViewDetails _gridViewDetails;
 
@@ -43,8 +51,9 @@ public HashSet<int> Start(ApplicationData applicationData)
             List<string> gridHeaders = _applicationData.DataTable.DataColumns.Select((c) => c.Label).ToList();
             CalculateColumnWidths(gridHeaders);
 
-            // Copy DataTable into the ListView's DataSource
-            _itemSource = LoadData();
+            // Copy the input DataTable into our master ListView source list; upon exit any items
+            // that are IsMarked are returned (if Outputmode is set)
+            _inputSource = LoadData();
 
             if (!_applicationData.MinUI)
             {
@@ -60,7 +69,9 @@ public HashSet<int> Start(ApplicationData applicationData)
             // Status bar is where our key-bindings are handled
             AddStatusBar(!_applicationData.MinUI);
 
-            // If -Filter parameter is set, apply it. 
+            // We *always* apply a filter, even if the -Filter parameter is not set or Filtering is not
+            // available. The ListView always shows a fitlered version of _inputSource even if there is no
+            // actual fitler. 
             ApplyFilter();
 
             _listView.SetFocus();
@@ -76,10 +87,8 @@ public HashSet<int> Start(ApplicationData applicationData)
                 return selectedIndexes;
             }
 
-            // Ensure that only items that are marked AND not filtered out
-            // get returned (See Issue #121)
-            List<GridViewRow> itemList = GridViewHelpers.FilterData(_itemSource.GridViewRowList, _applicationData.Filter);
-            foreach (GridViewRow gvr in itemList)
+            // Return any items that were selected.
+            foreach (GridViewRow gvr in _inputSource.GridViewRowList)
             {
                 if (gvr.IsMarked)
                 {
@@ -109,6 +118,7 @@ private GridViewDataSource LoadData()
                 items.Add(new GridViewRow
                 {
                     DisplayString = displayString,
+                    // We use this to keep _inputSource up to date when a filter is applied
                     OriginalIndex = i
                 });
 
@@ -120,9 +130,22 @@ private GridViewDataSource LoadData()
 
         private void ApplyFilter()
         {
-            List<GridViewRow> itemList = GridViewHelpers.FilterData(_itemSource.GridViewRowList, _applicationData.Filter ?? string.Empty);
-            // Set the ListView to show only the subset defined by the filter
-            _listView.Source = new GridViewDataSource(itemList);
+            // The ListView is always filled with a (filtered) copy of _inputSource.
+            // We listen for `MarkChanged` events on this filtered list and apply those changes up to _inputSource.
+
+            if (_listViewSource != null) {
+                _listViewSource.MarkChanged -= ListViewSource_MarkChanged;
+                _listViewSource = null;
+            }
+
+            _listViewSource = new GridViewDataSource(GridViewHelpers.FilterData(_inputSource.GridViewRowList, _applicationData.Filter ?? string.Empty));
+            _listViewSource.MarkChanged +=  ListViewSource_MarkChanged;
+            _listView.Source = _listViewSource;
+        }
+
+        private void ListViewSource_MarkChanged (object s, GridViewDataSource.RowMarkedEventArgs a)
+        {
+                _inputSource.GridViewRowList[a.Row.OriginalIndex].IsMarked = a.Row.IsMarked;
         }
 
         private void Accept()
@@ -198,7 +221,7 @@ private void AddStatusBar(bool visible)
                         // when ENTER is pressed in Single mode. If something was previously selected
                         // (using SPACE) then honor that as the single item to return
                         if (_applicationData.OutputMode == OutputModeOption.Single &&
-                            _itemSource.GridViewRowList.Find(i => i.IsMarked) == null)
+                            _inputSource.GridViewRowList.Find(i => i.IsMarked) == null)
                         {
                             _listView.MarkUnmarkRow();
                         }
@@ -315,7 +338,7 @@ private void AddFilter(Window win)
                     filterErrorLabel.Text = ex.Message;
                     filterErrorLabel.ColorScheme = Colors.Error;
                     filterErrorLabel.Redraw(filterErrorLabel.Bounds);
-                    _listView.Source = _itemSource;
+                    _listView.Source = _inputSource;
                 }
             };
 
@@ -370,7 +393,7 @@ private void AddHeaders(Window win, List<string> gridHeaders)
 
         private void AddListView(Window win)
         {
-            _listView = new ListView(_itemSource);
+            _listView = new ListView(_inputSource);
             _listView.X = MARGIN_LEFT;
             if (!_applicationData.MinUI)
             {

src/Microsoft.PowerShell.ConsoleGuiTools/GridViewDataSource.cs

@@ -32,9 +32,23 @@ public void Render(ListView container, ConsoleDriver driver, bool selected, int
 
         public void SetMark(int item, bool value)
         {
+            var oldValue = GridViewRowList[item].IsMarked;
             GridViewRowList[item].IsMarked = value;
+            var args = new RowMarkedEventArgs() { 
+                Row = GridViewRowList[item],
+                OldValue = oldValue
+            };
+            MarkChanged?.Invoke(this, args);
         }
 
+        public class RowMarkedEventArgs : EventArgs {
+            public GridViewRow Row { get; set;}
+            public bool OldValue { get ; set;}
+
+        }
+
+        public event EventHandler<RowMarkedEventArgs> MarkChanged;
+
         public IList ToList()
         {
             return GridViewRowList;

src/Microsoft.PowerShell.ConsoleGuiTools/GridViewHelpers.cs

@@ -24,7 +24,7 @@ public static List<GridViewRow> FilterData(List<GridViewRow> list, string filter
 
             foreach (GridViewRow gvr in list)
             {
-                if(Regex.IsMatch(gvr.DisplayString, filter, RegexOptions.IgnoreCase))
+                if (gvr.IsMarked || Regex.IsMatch(gvr.DisplayString, filter, RegexOptions.IgnoreCase))
                 {
                     items.Add(gvr);
                 }