Implement bottom Padding for Dialog buttons - WIP

- Modified Dialog.AddButton() to add buttons to Padding when available
- Added EndInit() override to move buttons from Dialog to Padding
- Added UpdatePaddingBottom() to set Padding thickness based on button height
- Added FrameChanged event handler for dynamic padding updates
- Updated MessageBox tests to reflect new layout (buttons in separate Padding area)
- Dialog tests still passing

Co-authored-by: tig <585482+tig@users.noreply.github.com>

Terminal.Gui/Views/Dialog.cs

@@ -49,6 +49,7 @@ public class Dialog : Window
     }
 
     private readonly List<Button> _buttons = [];
+    private bool _endInitCalled;
 
     private bool _canceled;
 
@@ -63,8 +64,26 @@ public class Dialog : Window
         button.X = Pos.Align (ButtonAlignment, ButtonAlignmentModes, GetHashCode ());
         button.Y = Pos.AnchorEnd ();
 
+        // Subscribe to FrameChanged to update padding dynamically
+        button.FrameChanged += Button_FrameChanged;
+
         _buttons.Add (button);
-        Add (button);
+
+        // Add to Padding if it exists and EndInit has been called, otherwise add to the Dialog
+        if (Padding is { } && _endInitCalled)
+        {
+            Padding.Add (button);
+            UpdatePaddingBottom ();
+        }
+        else
+        {
+            Add (button);
+        }
+    }
+
+    private void Button_FrameChanged (object? sender, EventArgs e)
+    {
+        UpdatePaddingBottom ();
     }
 
     // TODO: Update button.X = Pos.Justify when alignment changes
@@ -197,4 +216,52 @@ public class Dialog : Window
 
         return false;
     }
+
+    /// <inheritdoc/>
+    public override void EndInit ()
+    {
+        // Move buttons from the Dialog to the Padding
+        if (Padding is { })
+        {
+            foreach (Button button in _buttons)
+            {
+                // Remove from Dialog if it was added there
+                Remove (button);
+
+                // Add to Padding
+                Padding.Add (button);
+            }
+
+            UpdatePaddingBottom ();
+        }
+
+        _endInitCalled = true;
+        base.EndInit ();
+    }
+
+    private void UpdatePaddingBottom ()
+    {
+        if (Padding is null || _buttons.Count == 0)
+        {
+            return;
+        }
+
+        // Find the maximum button height
+        var maxHeight = 0;
+
+        foreach (Button button in _buttons)
+        {
+            if (button.Frame.Height > maxHeight)
+            {
+                maxHeight = button.Frame.Height;
+            }
+        }
+
+        // Set the bottom padding to match button height
+        // Use at least 1 as a minimum if buttons haven't been laid out yet
+        if (maxHeight > 0 || Padding.Thickness.Bottom == 0)
+        {
+            Padding.Thickness = Padding.Thickness with { Bottom = Math.Max (1, maxHeight) };
+        }
+    }
 }

Tests/UnitTestsParallelizable/Views/MessageBoxTests.cs

@@ -361,7 +361,7 @@ public class MessageBoxTests (ITestOutputHelper output)
   ║ff ff ff ff ff║
   ║ff ff ff ff ff║
   ║ff ff ff ff ff║
-  ║    ff ff     ║
+  ║              ║
   ║     ⟦► btn ◄⟧║
   ╚══════════════╝",
                                                                    output,
@@ -382,7 +382,8 @@ public class MessageBoxTests (ITestOutputHelper output)
  ║ffffffffffffffff║
  ║ffffffffffffffff║
  ║ffffffffffffffff║
- ║fffffff⟦► btn ◄⟧║
+ ║                ║
+ ║       ⟦► btn ◄⟧║
  ╚════════════════╝",
                                                                    output,
                                                                    app.Driver);