update player list in lobby gracefully for better user experience

OpenRA.Game/Widgets/GridLayout.cs

@@ -41,6 +41,11 @@ namespace OpenRA.Widgets
 
 			widget.ContentHeight = Math.Max(widget.ContentHeight, pos.Y + widget.ItemSpacing + w.Bounds.Height);
 		}
+
+		public void AdjustChildren()
+		{
+
+		}
 	}
 }
 

OpenRA.Game/Widgets/ListLayout.cs

@@ -24,5 +24,16 @@ namespace OpenRA.Widgets
 			w.Bounds.Y += widget.ContentHeight;
 			widget.ContentHeight += w.Bounds.Height + widget.ItemSpacing;
 		}
+
+
+		public void AdjustChildren()
+		{
+			widget.ContentHeight = widget.ItemSpacing;
+			foreach (var w in widget.Children)
+			{
+				w.Bounds.Y = widget.ContentHeight;
+				widget.ContentHeight += w.Bounds.Height + widget.ItemSpacing;
+			}
+		}
 	}
 }

OpenRA.Game/Widgets/ScrollPanelWidget.cs

@@ -14,7 +14,7 @@ using OpenRA.Graphics;
 
 namespace OpenRA.Widgets
 {
-	public interface ILayout { void AdjustChild(Widget w); }
+	public interface ILayout { void AdjustChild(Widget w); void AdjustChildren(); }
 
 	public class ScrollPanelWidget : Widget
 	{
@@ -95,6 +95,8 @@ namespace OpenRA.Widgets
 
 			Game.Renderer.EnableScissor(backgroundRect.X + 1, backgroundRect.Y + 1, backgroundRect.Width - 2, backgroundRect.Height - 2);
 
+			Layout.AdjustChildren();
+
 			foreach (var child in Children)
 				child.DrawOuter();
 

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

@@ -327,19 +327,26 @@ namespace OpenRA.Mods.RA.Widgets.Logic
 		{
 			// This causes problems for people who are in the process of editing their names (the widgets vanish from beneath them)
 			// Todo: handle this nicer
-			Players.RemoveChildren();
 
+			var idx = 0;
 			foreach (var kv in orderManager.LobbyInfo.Slots)
 			{
 				var key = kv.Key;
 				var slot = kv.Value;
 				var client = orderManager.LobbyInfo.ClientInSlot(key);
-				Widget template;
+				Widget template = null;
+
+				// get template for possible reuse
+				if (idx < Players.Children.Count)
+					template = Players.Children [idx];
 
 				// Empty slot
 				if (client == null)
 				{
+					//template = EmptySlotTemplate.Clone();
+					if (template == null || template.Id != EmptySlotTemplate.Id)
 						template = EmptySlotTemplate.Clone();
+
 					Func<string> getText = () => slot.Closed ? "Closed" : "Open";
 					var ready = orderManager.LocalClient.IsReady;
 
@@ -367,7 +374,9 @@ namespace OpenRA.Mods.RA.Widgets.Logic
 				else if ((client.Index == orderManager.LocalClient.Index) ||
 						 (client.Bot != null && Game.IsHost))
 				{
+					if (template == null || template.Id != EditablePlayerTemplate.Id)
 						template = EditablePlayerTemplate.Clone();
+
 					var botReady = client.Bot != null && Game.IsHost && orderManager.LocalClient.IsReady;
 					var ready = botReady || client.IsReady;
 
@@ -422,7 +431,9 @@ namespace OpenRA.Mods.RA.Widgets.Logic
 				}
 				else
 				{	// Non-editable player in slot
+					if (template == null || template.Id != NonEditablePlayerTemplate.Id)
 						template = NonEditablePlayerTemplate.Clone();
+
 					template.Get<LabelWidget>("NAME").GetText = () => client.Name;
 					if (client.IsAdmin)
 						template.Get<LabelWidget>("NAME").Font = "Bold";
@@ -449,20 +460,35 @@ namespace OpenRA.Mods.RA.Widgets.Logic
 				}
 
 				template.IsVisible = () => true;
+
+				if (idx >= Players.Children.Count)
 					Players.AddChild(template);
+				else if (Players.Children [idx].Id != template.Id)
+				{
+					Players.Children [idx].Removed();
+					template.Parent = Players;
+					Players.Children [idx] = template;
+				}
+				idx++;
 			}
 
 			// Add spectators
 			foreach (var client in orderManager.LobbyInfo.Clients.Where(client => client.Slot == null))
 			{
-				Widget template;
+				Widget template = null;
 				var c = client;
 				var ready = c.IsReady;
 
+				// get template for possible reuse
+				if (idx < Players.Children.Count)
+				template = Players.Children[idx];
+
 				// Editable spectator
 				if (c.Index == orderManager.LocalClient.Index)
 				{
+					if (template == null || template.Id != EditableSpectatorTemplate.Id)
 						template = EditableSpectatorTemplate.Clone();
+
 					var name = template.Get<TextFieldWidget>("NAME");
 					name.IsDisabled = () => ready;
 					LobbyUtils.SetupNameWidget(orderManager, c, name);
@@ -481,7 +507,9 @@ namespace OpenRA.Mods.RA.Widgets.Logic
 				// Non-editable spectator
 				else
 				{
+					if (template == null || template.Id != NonEditableSpectatorTemplate.Id)
 						template = NonEditableSpectatorTemplate.Clone();
+
 					template.Get<LabelWidget>("NAME").GetText = () => c.Name;
 					if (client.IsAdmin)
 						template.Get<LabelWidget>("NAME").Font = "Bold";
@@ -497,8 +525,20 @@ namespace OpenRA.Mods.RA.Widgets.Logic
 				}
 
 				template.IsVisible = () => true;
+
+				if (idx >= Players.Children.Count)
 					Players.AddChild(template);
+				else if (Players.Children [idx].Id != template.Id)
+				{
+					Players.Children [idx].Removed();
+					template.Parent = Players;
+					Players.Children [idx] = template;
 				}
+				idx++;
+			}
+
+			for (var i = idx; i < Players.Children.Count; i++)
+				Players.RemoveChild(Players.Children[i]);
 
 			// Spectate button
 			if (orderManager.LocalClient.Slot != null)