[ComboBox] Close dropdown on mouse up instead of mouse down.

Author: jpobst

src/Modern.Forms/ComboBox.cs

@@ -11,14 +11,14 @@ public class ComboBox : Control
     {
         private PopupWindow? popup;
         private readonly ListBox popup_listbox;
-        private bool suppress_popup_close;
 
         /// <summary>
         /// Initializes a new instance of the ComboBox class.
         /// </summary>
         public ComboBox ()
         {
             popup_listbox = new ListBox { Dock = DockStyle.Fill, ShowHover = true };
+            popup_listbox.MouseUp += ListBox_OnMouseUp;
             popup_listbox.SelectedIndexChanged += ListBox_SelectedIndexChanged;
         }
 
@@ -48,6 +48,8 @@ protected override void Dispose (bool disposing)
             popup?.Close ();
             popup = null;
 
+            popup_listbox.MouseUp -= ListBox_OnMouseUp;
+            popup_listbox.SelectedIndexChanged -= ListBox_SelectedIndexChanged;
             popup_listbox.Dispose ();
         }
 
@@ -92,13 +94,17 @@ public bool DroppedDown {
         /// </summary>
         public ListBoxItemCollection Items => popup_listbox.Items;
 
+        // We need to close the dropdown on mouse up instead of mouse down so
+        // that the mouse click/up events don't leak to the control underneath the dropdown.
+        private void ListBox_OnMouseUp (object? sender, MouseEventArgs e)
+        {
+            DroppedDown = false;
+        }
+
         // When the selected item of the popup ListBox changes, update the ComboBox
         private void ListBox_SelectedIndexChanged (object? sender, EventArgs e)
         {
             if (popup_listbox.SelectedIndex > -1) {
-                if (!suppress_popup_close)
-                    DroppedDown = false;
-
                 Invalidate ();
 
                 OnSelectedIndexChanged (e);
@@ -148,11 +154,7 @@ protected override void OnKeyUp (KeyEventArgs e)
                 return;
             }
 
-            // If you mouse click an item we automatically close the dropdown,
-            // we don't want that behavior when using the keyboard.
-            suppress_popup_close = true;
             popup_listbox.RaiseKeyUp (e);
-            suppress_popup_close = false;
 
             if (e.Handled)
                 return;