factor out layout policy for ScrollPanelWidget; add GridLayout option.

OpenRA.Game/Widgets/GridLayout.cs

@@ -0,0 +1,46 @@
+#region Copyright & License Information
+/*
+ * Copyright 2007-2011 The OpenRA Developers (see AUTHORS)
+ * This file is part of OpenRA, which is free software. It is made
+ * available to you under the terms of the GNU General Public License
+ * as published by the Free Software Foundation. For more information,
+ * see COPYING.
+ */
+#endregion
+
+using System;
+
+namespace OpenRA.Widgets
+{
+	public class GridLayout : ILayout
+	{
+		ScrollPanelWidget widget;
+		int2 pos;
+
+		public GridLayout(ScrollPanelWidget w) { widget = w; }
+
+		public void AdjustChild(Widget w)
+		{
+			if (widget.Children.Count == 0)
+			{
+				widget.ContentHeight = widget.ItemSpacing;
+				pos = new int2(widget.ItemSpacing, widget.ItemSpacing);
+			}
+			
+			if (pos.X + widget.ItemSpacing + w.Bounds.Width > widget.Bounds.Width - widget.ScrollbarWidth)
+			{
+				/* start a new row */
+				pos.X = widget.ItemSpacing;
+				pos.Y = widget.ContentHeight;
+			}
+			
+			w.Bounds.X += pos.X;
+			w.Bounds.Y += pos.Y;
+			
+			pos.X += widget.Bounds.Width + widget.ItemSpacing;
+
+			widget.ContentHeight = Math.Max(widget.ContentHeight, pos.Y + widget.ItemSpacing + w.Bounds.Height);
+		}
+	}
+}
+