Fixes #5126. TableView: don't raise Activating when click is outside any cell

Terminal.Gui/Views/TableView/TableView.cs

@@ -238,6 +238,25 @@ private bool IsColumnVisible (int columnIndex)
         return Style.GetColumnStyleIfAny (columnIndex)?.Visible ?? true;
     }
 
+    /// <inheritdoc />
+    protected override bool OnActivating (CommandEventArgs args)
+    {
+        // Cancel Activate when a mouse click lands outside any cell (e.g. below the
+        // last row or in the header area). Without this, the Activating event would
+        // fire even though no cell was actually selected, surprising subscribers.
+        if (!TryGetMouseCellHit (args.Context, out Point? hit))
+        {
+            return false;
+        }
+
+        if (hit is null)
+        {
+            return true;
+        }
+
+        return false;
+    }
+
     /// <inheritdoc />
     protected override void OnActivated (ICommandContext? ctx)
     {
@@ -248,26 +267,65 @@ protected override void OnActivated (ICommandContext? ctx)
             return;
         }
 
-        if (ctx?.Binding is not MouseBinding mouseBinding || mouseBinding.MouseEvent is null)
+        if (!TryGetMouseCellHit (ctx, out Point? hit) || hit is null)
         {
             return;
         }
-        int boundsX = mouseBinding.MouseEvent.Position!.Value.X;
-        int boundsY = mouseBinding.MouseEvent.Position!.Value.Y;
+
+        MouseBinding mouseBinding = (MouseBinding)ctx!.Binding!;
+        SetSelection (hit.Value.X, hit.Value.Y, mouseBinding.MouseEvent!.Flags.FastHasFlags (MouseFlags.Shift));
+
+        Update ();
+    }
+
+    // Returns true when the binding represents a left-click on this TableView; in that case
+    // hit is the cell that was clicked, or null if the click was outside any cell (e.g. header,
+    // below the last row, or right of the last rendered column). Returns false for non-mouse or
+    // non-left-click bindings.
+    private bool TryGetMouseCellHit (ICommandContext? ctx, out Point? hit)
+    {
+        hit = null;
+
+        if (ctx?.Binding is not MouseBinding mouseBinding || mouseBinding.MouseEvent is null)
+        {
+            return false;
+        }
 
         if (!mouseBinding.MouseEvent.Flags.FastHasFlags (MouseFlags.LeftButtonClicked))
         {
-            return;
+            return false;
         }
-        Point? hit = ScreenToCell (boundsX, boundsY);
 
-        if (hit is null)
+        int clientX = mouseBinding.MouseEvent.Position!.Value.X;
+        int clientY = mouseBinding.MouseEvent.Position!.Value.Y;
+
+        hit = ScreenToCell (clientX, clientY);
+
+        // ScreenToCell maps far-right X positions onto the last column (its column lookup picks
+        // the largest X with X <= clientX, with no upper-bound check). When ExpandLastColumn is
+        // false there is visible whitespace to the right of the last rendered column; reject
+        // hits that fall there so clicks in that whitespace don't raise Activating.
+        if (hit is not null && !IsXWithinAnyRenderedColumn (clientX))
         {
-            return;
+            hit = null;
         }
-        SetSelection (hit.Value.X, hit.Value.Y, mouseBinding.MouseEvent.Flags.FastHasFlags (MouseFlags.Shift));
 
-        Update ();
+        return true;
+    }
+
+    private bool IsXWithinAnyRenderedColumn (int clientX)
+    {
+        int viewportX = clientX + Viewport.X;
+
+        foreach (ColumnToRender col in NonHiddenCellInfos ())
+        {
+            if (viewportX >= col.X && viewportX < col.X + col.Width)
+            {
+                return true;
+            }
+        }
+
+        return false;
     }
 
     /// <inheritdoc/>

Tests/UnitTestsParallelizable/Views/TableViewTests.cs

@@ -1141,4 +1141,180 @@ public void HeaderSeparatorLines_DoNotUseFocusAttribute_WhenTableHasFocus ()
 
         tableView.Dispose ();
     }
+
+    // Claude - Opus 4.7
+    // Regression test for https://github.com/gui-cs/Terminal.Gui/issues/5126
+    // Clicking outside the row area of a TableView (e.g. below the last row) must
+    // not raise the Activating event.
+    [Fact]
+    public void Click_OutsideRows_DoesNotRaise_Activating ()
+    {
+        TableView tableView = new () { Viewport = new Rectangle (0, 0, 25, 10) };
+        tableView.Table = BuildTable (2, 2);
+
+        var activatingFired = 0;
+        tableView.Activating += (_, _) => activatingFired++;
+
+        // Construct a left-click well below the last data row. With a 2-row table,
+        // y=9 is past the rows so ScreenToCell returns null.
+        Mouse mouseEvent = new ()
+        {
+            Position = new Point (1, 9),
+            Flags = MouseFlags.LeftButtonClicked
+        };
+
+        MouseBinding binding = new ([Command.Activate], mouseEvent);
+
+        tableView.InvokeCommand (Command.Activate, binding);
+
+        Assert.Equal (0, activatingFired);
+
+        tableView.Dispose ();
+    }
+
+    // Claude - Opus 4.7
+    // Companion to Click_OutsideRows_DoesNotRaise_Activating: clicking on a real
+    // cell still raises Activating as before.
+    [Fact]
+    public void Click_OnRow_Raises_Activating ()
+    {
+        TableView tableView = new () { Viewport = new Rectangle (0, 0, 25, 10) };
+        tableView.Table = BuildTable (2, 2);
+
+        var activatingFired = 0;
+        tableView.Activating += (_, _) => activatingFired++;
+
+        // y=3 lands on the first data row. The default header style consumes 3 lines
+        // (overline + header text + underline), so y=0..2 is header and y=3 is the
+        // first data row.
+        Mouse mouseEvent = new ()
+        {
+            Position = new Point (1, 3),
+            Flags = MouseFlags.LeftButtonClicked
+        };
+
+        MouseBinding binding = new ([Command.Activate], mouseEvent);
+
+        tableView.InvokeCommand (Command.Activate, binding);
+
+        Assert.Equal (1, activatingFired);
+
+        tableView.Dispose ();
+    }
+
+    // Claude - Opus 4.7
+    // Click in horizontal whitespace (right of the last rendered column) must not
+    // raise Activating. Disable ExpandLastColumn so the last column doesn't fill
+    // the viewport and there is real whitespace to the right.
+    [Fact]
+    public void Click_RightOfLastColumn_DoesNotRaise_Activating ()
+    {
+        TableView tableView = new () { Viewport = new Rectangle (0, 0, 40, 10) };
+        tableView.Style.ExpandLastColumn = false;
+        tableView.Table = BuildTable (2, 2);
+
+        var activatingFired = 0;
+        tableView.Activating += (_, _) => activatingFired++;
+
+        // BuildTable column "Col0" / "Col1" rendered with values like "R0C0" gives
+        // narrow columns. With ExpandLastColumn=false and viewport width 40, x=35 is
+        // well past the right edge of the last rendered column.
+        Mouse mouseEvent = new ()
+        {
+            Position = new Point (35, 3),
+            Flags = MouseFlags.LeftButtonClicked
+        };
+
+        MouseBinding binding = new ([Command.Activate], mouseEvent);
+
+        tableView.InvokeCommand (Command.Activate, binding);
+
+        Assert.Equal (0, activatingFired);
+
+        tableView.Dispose ();
+    }
+
+    // Claude - Opus 4.7
+    // Click on the column header area must not raise Activating — the click
+    // doesn't correspond to a data cell.
+    [Fact]
+    public void Click_OnHeader_DoesNotRaise_Activating ()
+    {
+        TableView tableView = new () { Viewport = new Rectangle (0, 0, 25, 10) };
+        tableView.Table = BuildTable (2, 2);
+
+        var activatingFired = 0;
+        tableView.Activating += (_, _) => activatingFired++;
+
+        // The header occupies y=0..2 (overline + header text + underline). y=1 is
+        // the header text line.
+        Mouse mouseEvent = new ()
+        {
+            Position = new Point (1, 1),
+            Flags = MouseFlags.LeftButtonClicked
+        };
+
+        MouseBinding binding = new ([Command.Activate], mouseEvent);
+
+        tableView.InvokeCommand (Command.Activate, binding);
+
+        Assert.Equal (0, activatingFired);
+
+        tableView.Dispose ();
+    }
+
+    // Claude - Opus 4.7
+    // Click on a TableView with no Table set must not raise Activating.
+    [Fact]
+    public void Click_EmptyTable_DoesNotRaise_Activating ()
+    {
+        TableView tableView = new () { Viewport = new Rectangle (0, 0, 25, 10) };
+
+        // Intentionally no Table assigned.
+        var activatingFired = 0;
+        tableView.Activating += (_, _) => activatingFired++;
+
+        Mouse mouseEvent = new ()
+        {
+            Position = new Point (5, 5),
+            Flags = MouseFlags.LeftButtonClicked
+        };
+
+        MouseBinding binding = new ([Command.Activate], mouseEvent);
+
+        tableView.InvokeCommand (Command.Activate, binding);
+
+        Assert.Equal (0, activatingFired);
+
+        tableView.Dispose ();
+    }
+
+    // Claude - Opus 4.7
+    // Click on a Table that has zero rows (header rendered but no data) must not
+    // raise Activating regardless of where in the data area the user clicks.
+    [Fact]
+    public void Click_TableWithZeroRows_DoesNotRaise_Activating ()
+    {
+        TableView tableView = new () { Viewport = new Rectangle (0, 0, 25, 10) };
+        tableView.Table = BuildTable (2, 0);
+
+        var activatingFired = 0;
+        tableView.Activating += (_, _) => activatingFired++;
+
+        // y=3 is just past the header, in what would be the first data row if any
+        // existed. With zero rows, ScreenToCell must return null.
+        Mouse mouseEvent = new ()
+        {
+            Position = new Point (1, 3),
+            Flags = MouseFlags.LeftButtonClicked
+        };
+
+        MouseBinding binding = new ([Command.Activate], mouseEvent);
+
+        tableView.InvokeCommand (Command.Activate, binding);
+
+        Assert.Equal (0, activatingFired);
+
+        tableView.Dispose ();
+    }
 }