Remove OnMouseDown from Widget. Define it on just the widgets that want it.

OpenRA.Game/Widgets/ButtonWidget.cs

@@ -24,6 +24,8 @@ namespace OpenRA.Widgets
 		public string Font = ChromeMetrics.Get<string>("ButtonFont");
 		public Func<string> GetText;
 		public Func<bool> IsDisabled = () => false;
+		public Func<MouseInput, bool> OnMouseDown = mi => false;
+
 		public Action OnClick = () => {};
 		public Action<KeyInput> OnKeyPress = _ => {};
 		
@@ -43,6 +45,8 @@ namespace OpenRA.Widgets
 			Depressed = widget.Depressed;
 			VisualHeight = widget.VisualHeight;
 			GetText = widget.GetText;
+			OnMouseDown = widget.OnMouseDown;
+
 			OnMouseUp = mi => { if (!IsDisabled()) OnClick(); return true; };
 			OnKeyPress = _ => OnClick();
 		}

OpenRA.Game/Widgets/DropDownButtonWidget.cs

@@ -18,7 +18,7 @@ namespace OpenRA.Widgets
 	public class DropDownButtonWidget : ButtonWidget
 	{
 		Widget panel;
-		Widget fullscreenMask;
+		MaskWidget fullscreenMask;
 		
 		public DropDownButtonWidget()
 			: base()
@@ -75,17 +75,11 @@ namespace OpenRA.Widgets
 			panel = p;
 			
 			// Mask to prevent any clicks from being sent to other widgets
-			fullscreenMask = new ContainerWidget();
+			fullscreenMask = new MaskWidget();
 			fullscreenMask.Bounds = new Rectangle(0, 0, Game.viewport.Width, Game.viewport.Height);
+			fullscreenMask.OnMouseDown = mi => RemovePanel();
 			Widget.RootWidget.AddChild(fullscreenMask);
 
-			fullscreenMask.OnMouseDown = mi =>
-			{
-				RemovePanel();
-				return true;
-			};
-			fullscreenMask.OnMouseUp = mi => true;
-
 			var oldBounds = panel.Bounds;
 			panel.Bounds = new Rectangle(RenderOrigin.X, RenderOrigin.Y + Bounds.Height, oldBounds.Width, oldBounds.Height);
 			Widget.RootWidget.AddChild(panel);
@@ -114,4 +108,30 @@ namespace OpenRA.Widgets
 			AttachPanel(panel);
 		}
 	}
+
+	public class MaskWidget : Widget
+    {
+       	public Action<MouseInput> OnMouseDown = _ => {};
+		public MaskWidget() : base() { }
+        public MaskWidget(MaskWidget other)
+            : base(other)
+		{
+			OnMouseDown = other.OnMouseDown;
+		}
+
+		public override bool HandleMouseInput(MouseInput mi)
+        {
+            if (mi.Event != MouseInputEvent.Down && mi.Event != MouseInputEvent.Up)
+				return false;
+
+			if (mi.Event == MouseInputEvent.Down)
+				OnMouseDown(mi);
+
+			return true;
+        }
+
+        public override void DrawInner() { }
+        public override string GetCursor(int2 pos) { return null; }
+        public override Widget Clone() { return new MaskWidget(this); }
+    }
 }

OpenRA.Game/Widgets/MapPreviewWidget.cs

@@ -20,6 +20,8 @@ namespace OpenRA.Widgets
 	{
 		public Func<Map> Map = () => null;
 		public Func<Dictionary<int2, Color>> SpawnColors = () => new Dictionary<int2, Color>();
+		public Action<MouseInput> OnMouseDown = _ => {};
+
 		Cache<Map,Bitmap> PreviewCache = new Cache<Map, Bitmap>(stub => Minimap.RenderMapPreview( new Map( stub.Path )));
 		
 		public MapPreviewWidget() : base() { }
@@ -32,6 +34,15 @@ namespace OpenRA.Widgets
 		}
 		public override Widget Clone() { return new MapPreviewWidget(this); }
 
+		public override bool HandleMouseInput(MouseInput mi)
+        {
+			if (mi.Event != MouseInputEvent.Down)
+				return false;
+
+            OnMouseDown(mi);
+            return true;
+        }
+
 		public int2 ConvertToPreview(Map map, int2 point)
 		{
 			return new int2(MapRect.X + (int)(PreviewScale*(point.X - map.Bounds.Left)) , MapRect.Y + (int)(PreviewScale*(point.Y - map.Bounds.Top)));

OpenRA.Game/Widgets/Widget.cs

@@ -38,7 +38,6 @@ namespace OpenRA.Widgets
         static Stack<Widget> WindowList = new Stack<Widget>();
 
         // Common Funcs that most widgets will want
-        public Func<MouseInput, bool> OnMouseDown = mi => false;
         public Func<MouseInput, bool> OnMouseUp = mi => false;
 
         public Func<bool> IsVisible;
@@ -65,7 +64,6 @@ namespace OpenRA.Widgets
             Bounds = widget.Bounds;
             Parent = widget.Parent;
 
-            OnMouseDown = widget.OnMouseDown;
             OnMouseUp = widget.OnMouseUp;
 
             IsVisible = widget.IsVisible;
@@ -226,7 +224,6 @@ namespace OpenRA.Widgets
         public virtual bool HandleMouseInput(MouseInput mi)
         {
             // Apply any special logic added by event handlers; they return true if they caught the input
-            if (mi.Event == MouseInputEvent.Down && OnMouseDown(mi)) return true;
             if (mi.Event == MouseInputEvent.Up && OnMouseUp(mi)) return true;
 
             return false;

OpenRA.Mods.Cnc/Widgets/Logic/CncLobbyLogic.cs

@@ -120,7 +120,7 @@ namespace OpenRA.Mods.Cnc.Widgets.Logic
 				var map = mapPreview.Map();
 				if (map == null || mi.Button != MouseButton.Left
 				    || orderManager.LocalClient.State == Session.ClientState.Ready)
-					return false;
+					return;
 
 				var p = map.SpawnPoints
 					.Select((sp, i) => Pair.New(mapPreview.ConvertToPreview(map, sp), i))
@@ -131,8 +131,6 @@ namespace OpenRA.Mods.Cnc.Widgets.Logic
 				var owned = orderManager.LobbyInfo.Clients.Any(c => c.SpawnPoint == p);
 				if (p == 0 || !owned)
 					orderManager.IssueOrder(Order.Command("spawn {0} {1}".F(orderManager.LocalClient.Index, p)));
-				
-				return true;
 			};
 
 			var mapTitle = lobby.GetWidget<LabelWidget>("MAP_TITLE");

OpenRA.Mods.RA/Widgets/Logic/LobbyLogic.cs

@@ -65,7 +65,7 @@ namespace OpenRA.Mods.RA.Widgets.Logic
 				var map = mapPreview.Map();
 				if (map == null || mi.Button != MouseButton.Left
 				    || orderManager.LocalClient.State == Session.ClientState.Ready)
-					return false;
+					return;
 
 				var p = map.SpawnPoints
 					.Select((sp, i) => Pair.New(mapPreview.ConvertToPreview(map, sp), i))
@@ -76,8 +76,6 @@ namespace OpenRA.Mods.RA.Widgets.Logic
 				var owned = orderManager.LobbyInfo.Clients.Any(c => c.SpawnPoint == p);
 				if (p == 0 || !owned)
 					orderManager.IssueOrder(Order.Command("spawn {0} {1}".F(orderManager.LocalClient.Index, p)));
-				
-				return true;
 			};
 
 			mapPreview.SpawnColors = () =>