[MWF] Fix ComboBox list to not display offscreen (#15462)

The fix mimics the behavior of Windows/.NET.

diff --git a/mcs/class/Managed.Windows.Forms/System.Windows.Forms/ComboBox.cs b/mcs/class/Managed.Windows.Forms/System.Windows.Forms/ComboBox.cs
index d58ad360c0b2f493ef6d83ddd05613269e015b3e..07bf3e56fb33e7343d9322d603f28da49c4dede5 100644 (file)
--- a/mcs/class/Managed.Windows.Forms/System.Windows.Forms/ComboBox.cs
+++ b/mcs/class/Managed.Windows.Forms/System.Windows.Forms/ComboBox.cs
@@ -2757,6 +2757,10 @@ namespace System.Windows.Forms
                                HighlightedIndex = owner.SelectedIndex;
 
                                CalcListBoxArea ();
+                               // If the listbox would extend below the screen, move it above the textbox.
+                               Rectangle scrn_rect = Screen.FromControl (owner).Bounds;
+                               if (this.Location.Y + this.Height >= scrn_rect.Bottom)
+                                       this.Location = new Point (this.Location.X, this.Location.Y - (this.Height + owner.TextArea.Height));
                                Show ();
 
                                Refresh ();