Gtk fix various treeview bugs

src/Eto.Gtk/Forms/Controls/GridHandler.cs

@@ -1,5 +1,6 @@
 using Eto.GtkSharp.Forms.Cells;
 using Eto.GtkSharp.Forms.Menu;
+
 namespace Eto.GtkSharp.Forms.Controls
 {
 	class GridHandler
@@ -138,12 +139,21 @@ protected override void Initialize()
 			columns.Register(Widget.Columns);
 			base.Initialize();
 
-			Widget.MouseDown += Widget_MouseDown;
+			Control.Selection.Changed += (sender, args) =>
+			{
+				// Prevent unselecting last selected item.
+				if (!AllowEmptySelection && AllowMultipleSelection && Control.Selection.CountSelectedRows() == 0)
+				{
+					Control.GetCursor(out var cursorRow, out _);
+					if (cursorRow != null)
+					{
+						Control.Selection.SelectPath(cursorRow);
+					}
+				}
+			};
 
 			Control.QueryTooltip += Control_QueryTooltip;
 			Control.HasTooltip = true;
-
-
 		}
 
 		private void Control_QueryTooltip(object o, Gtk.QueryTooltipArgs args)
@@ -534,7 +544,7 @@ public void ColumnClicked(GridColumnHandler column)
 		public bool AllowMultipleSelection
 		{
 			get { return Control.Selection.Mode == Gtk.SelectionMode.Multiple; }
-			set { Control.Selection.Mode = value ? Gtk.SelectionMode.Multiple : Gtk.SelectionMode.Browse; }
+			set => SetSelectionMode(AllowEmptySelection, value);
 		}
 
 		public virtual IEnumerable<int> SelectedRows
@@ -703,37 +713,46 @@ public bool IsEditing
 		public bool AllowEmptySelection
 		{
 			get => Widget.Properties.Get<bool>(GridHandler.AllowEmptySelection_Key, true);
-			set => Widget.Properties.TrySet(GridHandler.AllowEmptySelection_Key, value, true);
+			set
+			{
+				Widget.Properties.TrySet(GridHandler.AllowEmptySelection_Key, value, true);
+				SetSelectionMode(value, AllowMultipleSelection);
+			}
 		}
 
-		private void Widget_MouseDown(object sender, MouseEventArgs e)
+		private void SetSelectionMode(bool allowEmptySelection, bool allowMultipleSelection)
 		{
-			if (!e.Handled && e.Buttons == MouseButtons.Primary)
+			var currentMode = Control.Selection.Mode;
+			var newMode =
+				(allowEmptySelection, allowMultipleSelection) switch
+				{
+					(true, true) => Gtk.SelectionMode.Multiple,
+					(true, false) => Gtk.SelectionMode.Single,
+					(false, true) => Gtk.SelectionMode.Multiple, // Handled by Selection Changed event in Initialize().
+					(false, false) => Gtk.SelectionMode.Browse
+				};
+
+			if (newMode != currentMode)
 			{
-				var location = e.Location;
-				if (AllowEmptySelection)
+				// Workaround to not lose the ability to select after switching to Multi, unselecting everything,
+				// then switching back to Single or Browse. Cause unknown but reproduced in GtkSharp.
+				if (currentMode == Gtk.SelectionMode.Multiple
+				    && newMode is Gtk.SelectionMode.Single or Gtk.SelectionMode.Browse)
 				{
-					// clicked on an empty area
-					if (!Control.GetPathAtPos((int)location.X, (int)location.Y, out _, out _))
+					Control.GetCursor(out var cursorRowPath, out _);
+					var mustReselectCursor = cursorRowPath != null && Control.Selection.PathIsSelected(cursorRowPath);
+
+					Control.Selection.Mode = Gtk.SelectionMode.None;
+					Control.Selection.Mode = newMode;
+
+					if (mustReselectCursor)
 					{
-						UnselectAll();
-						e.Handled = true;
+						Control.Selection.SelectPath(cursorRowPath);
 					}
 				}
 				else
 				{
-					// cancel ctrl+clicking to remove last selected item
-					if (Control.GetPathAtPos((int)location.X, (int)location.Y, out var path, out _))
-					{
-						if (Control.Model.GetIter(out var iter, path))
-						{
-							var isSelected = Control.Selection.IterIsSelected(iter);
-							if (e.Modifiers == Keys.Control && isSelected && Control.Selection.CountSelectedRows() == 1)
-							{
-								e.Handled = true;
-							}
-						}
-					}
+					Control.Selection.Mode = newMode;
 				}
 			}
 		}

test/Eto.Test/UnitTests/Forms/Controls/GridViewSelectTests.cs

@@ -124,5 +124,36 @@ public void DeleteSelectedItemsShouldRemoveSelectedItems()
 				Assert.AreEqual(initialCount / 4, selectionChangedCount, "SelectionChanged event should fire for each selected item removed");
 			});
 		}
+
+		[Test]
+		public void UnselectingInMultipleModeThenSwitchingToSingleModeShouldNotBreakSelection()
+		{
+			TestBase.Shown(form =>
+			{
+				form.Content = grid;
+			}, () =>
+			{
+				grid.AllowEmptySelection = true;
+				grid.AllowMultipleSelection = true;
+				grid.UnselectAll();
+				grid.AllowMultipleSelection = false;
+				grid.SelectRow(1);
+				Assert.AreEqual(1, grid.SelectedRow);
+			});
+		}
+
+		[Test]
+		public void SwitchingToSingleModeDoesNotBreakUnselecting()
+		{
+			TestBase.Invoke(() =>
+			{
+				grid.AllowEmptySelection = true;
+				grid.AllowMultipleSelection = true;
+				grid.SelectRow(1);
+				grid.AllowMultipleSelection = false;
+				grid.UnselectAll();
+				Assert.AreEqual(-1, grid.SelectedRow);
+			});
+		}
 	}
 }